Stanford Encyclopedia of Philosophy Archive

Kant’s Transcendental Idealism

First published Fri Mar 4, 2016

In theCritique of Pure Reason Kant argues that space andtime are merely formal features of how we perceive objects, not thingsin themselves that exist independently of us, or properties orrelations among them. Objects in space and time are said to be“appearances”, and he argues that we know nothing ofsubstance about the things in themselves of which they areappearances. Kant calls this doctrine (or set of doctrines)“transcendental idealism”, and ever since the publicationof the first edition of theCritique of Pure Reason in 1781,Kant’s readers have wondered, and debated, what exactly transcendentalidealism is, and have developed quite different interpretations. Some,including many of Kant’s contemporaries, interpret transcendentalidealism as essentially a form of phenomenalism, similar in somerespects to that of Berkeley, while others think that it is not ametaphysical or ontological theory at all. There is probably no majorinterpretive question in Kant’s philosophy on which there is so littleconsensus. This entry provides an introduction to the most importantKantian texts, as well as the interpretive and philosophical issuessurrounding them.

1. Appearances and Things in Themselves

In the first edition (A) of theCritique of Pure Reason,published in 1781, Kant argues for a surprising set of claims aboutspace, time, and objects:

Space and time are merely the forms of our sensible intuition ofobjects. They are not beings that exist independently of our intuition(things in themselves), nor are they properties of, nor relationsamong, such beings. (A26, A33)
The objects we intuit in space and time are appearances, notobjects that exist independently of our intuition (things inthemselves). This is also true of the mental states we intuit inintrospection; in “inner sense” (introspective awarenessof my inner states) I intuit only how I appear to myself, not how I am“in myself”. (A37–8, A42)
We can only cognize objects that we can, in principle, intuit.Consequently, we can only cognize objects in space and time,appearances. We cannot cognize things in themselves. (A239)
Nonetheless, we can think about things in themselves using thecategories (A254).
Things in themselves affect us, activating our sensible faculty(A190, A387).^[1]

In the “Fourth Paralogism” Kant defines“transcendental idealism”:

I understand by thetranscendental idealism of allappearances [Erscheinungen] the doctrine that they are alltogether to be regarded as mere representations and not as things inthemselves [nicht als Dinge an sich selbst ansehen], andaccordingly that space and time are only sensible forms of ourintuition, but not determinations given for themselves or conditionsof objects as things in themselves [als Dinge an sichselbst]. (A369; theCritique is quoted from the Guyer& Wood translation (1998))

Ever since 1781, the meaning and significance of Kant’s“transcendental idealism” has been a subject ofcontroversy. Kant’s doctrines raise numerous interpretive questions,which cluster around three sets of issues:

(a): The nature ofappearances. Are they (as Kant sometimes suggests) identical torepresentations, i.e., states of our minds? If so, does Kant followBerkeley in equating bodies (objects in space) with ideas(representations)? If not, what are they, and what relation do theyhave to our representations of them?
(b): The nature ofthings in themselves. What can we say positively about them? Whatdoes it mean that they are not in space and time? How is this claimcompatible with the doctrine that we cannot know anything about them?How is the claim that they affect us compatible with that doctrine? IsKant committed to theexistence of things in themselves, oris the concept of a “thing in itself” merely the conceptof a way objects might be (for all we know)?
(c): The relationof things in themselves to appearances. Is the appearance/thingin itself distinction an ontological one between two different kindsof objects? If not, is it a distinction between two aspects of one andthe same kind of object? Or perhaps an adverbial distinction betweentwo different ways of considering the same objects?

Sections 2–6 examine various influential interpretations oftranscendental idealism, focusing on their consequences for(a)–(c). Section 7 is devoted more narrowly to the nature ofthings in themselves, topic (b), and the related Kantian notions:noumena, and the transcendental object. The primary focuswill be theCritique of Pure Reason itself; whiletranscendental idealism, arguably, plays an equally crucial role inthe otherCritiques, discussing them would take us too farafield into Kant’s ethics, aesthetics, and teleology.^[2] While transcendental idealism is a view both about spaceandtime, and thus of objects of outer sense as well as inner sense (myown mental states), this entry will focus on Kant’s views about spaceand outer objects. Kant’s transcendental idealist theory of time istoo intimately tied up with his theory of the self, and the argumentof the transcendental deduction, to discuss here (see Falkenstein1991; Van Cleve 1999: 52–61; and Dunlop 2009 for more on Kant’stheory of time).

Before discussing the details of different interpretations, though, itwill be helpful if readers have an overview of some relevant texts andsome sense of theirprima facie meaning. The interpretationof these texts offered in this section is provisional; later, we willsee powerful reasons to question whether it is correct. Since somescholars claim there is a change in Kant’s doctrine from the A editionof 1781 to the B edition of 1787, we will begin by restrictingattention to the A edition.Section 2.4 discusses what relevance the changes made in the B edition have forthe interpretation of transcendental idealism. However, followingstandard scholarly practice, for passages present in both editions,the A page number followed by the B page number is given (e.g.,A575/B603). Works other than theCritique are cited by volumein the “Academy” edition of Kant’s work (Ak.), followed bythe page number. At the end of this article can be found a guide toall the editions and translations of Kant used in its preparation.

1.1 Transcendental Realism and Empirical Idealism

One promising place to begin understanding transcendental idealism isto look at the other philosophical positions from which Kantdistinguishes it. In the “Fourth Paralogism”, hedistinguishes transcendental idealism from transcendental realism:

To this [transcendental] idealism is opposed transcendental realism,which regards space and time as something given in themselves(independent of our sensibility). The transcendental realist thereforerepresents outer appearances (if their reality is conceded) as thingsin themselves [Dinge an sich selbst], which would existindependently of us and our sensibility and thus would also be outsideus according to pure concepts of the understanding. (A369)

Transcendental realism, according to this passage, is the view thatobjects in space and time exist independently of our experience ofthem, while transcendental idealism denies this. This point isreiterated later in theCritique when Kant writes:

We have sufficiently proved in the Transcendental Aesthetic thateverything intuited in space or in time, hence all objects of anexperience possible for us, are nothing but appearances, i.e., mererepresentations, which, as they are represented, as extended beings orseries of alterations, have outside our thoughts no existence groundedin itself. This doctrine I calltranscendental idealism. The realist, in the transcendental signification, makesthese modifications of our sensibility into things subsisting inthemselves, and hence makes mererepresentations intothings in themselves [Sachen an sich selbst]. (A491/B519)^[3]

Appearances exist at least partly in virtue of our experience of them,while the existence of things in themselves is not grounded in ourexperience at all (cf. A369, A492/B521, A493/B522). Kant callstranscendental realism the “common prejudice” (A740/B768)and describes it as a “common but fallaciouspresupposition” (A536/B564; cf. Allison 2004: 22).Transcendental realism is the commonsense pre-theoretic view thatobjects in space and time are “things in themselves”,which Kant, of course, denies.

Kant also distinguishes transcendental idealism from another positionhe calls “empirical idealism”:

One would also do us an injustice if one tried to ascribe to us thatlong-decried empirical idealism that, while assuming the properreality of space, denies the existence of extended beings in it, or atleast finds this existence doubtful, and so in this respect admits nosatisfactorily provable distinction between dream and truth. As to theappearances of inner sense in time, it finds no difficulty in them asreal things, indeed, it even asserts that this inner experience and italone gives sufficient proof of the real existence of their object (initself) along with all this time-determination. (A491/B519)

Empirical idealism, as Kant here characterizes it, is the view thatall we know immediately (non-inferentially) is the existence of ourown minds and our temporally ordered mental states, while we can onlyinfer the existence of objects “outside” us in space.Since the inference from a known effect to an unknown cause is alwaysuncertain, the empirical idealist concludes we cannot know thatobjects exist outside us in space. Kant typically distinguishes twovarieties of empirical idealism: dogmatic idealism, which claims thatobjects in space do not exist, and problematic idealism, which claimsthat objects in space may exist, but we cannot know whether they do(see A377). Although he is never mentioned by name in the A Edition,Berkeley seems to be Kant’s paradigm dogmatic idealist, whileDescartes is named as the paradigm problematic idealist.^[4]

Transcendental idealism is a form of empirical realism because itentails that we have immediate (non-inferential) and certain knowledgeof the existence of objects in space merely throughself-consciousness:

[…] external objects (bodies) are merely appearances, hencealso nothing other than a species of my representations, whose objectsare something only through these representations, but are nothingseparated from them. Thus external things exist as well as my self,and indeed both exist on the immediate testimony of myself-consciousness, only with this difference: the representation ofmy Self, as the thinking subject is related merely to inner sense, butthe representations that designate extended beings are also related toouter sense. I am no more necessitated to draw inferences in respectof the reality of external objects than I am in regard to the realityof my inner sense (my thoughts), for in both cases they are nothingbut representations, the immediate perception (consciousness) of whichis at the same time a sufficient proof of their reality.(A370–1)

Merely through self-conscious introspection I can know that I haverepresentations with certain contents and since appearances are“nothing other than a species of my representations” thisconstitutes immediate and certain knowledge of the existence ofobjects in space.

Understanding transcendental idealism requires understanding theprecise sense in which things in themselves are, and appearances arenot, “external to” or “independent” of themind and Kant draws a helpful distinction between two senses in whichobjects can be “outside me”:

But since the expressionoutside us carries with itan unavoidable ambiguity, since it sometimes signifies something that,as a thing in itself [Ding an sich selbst], exists distinctfrom us and sometimes merely that belongs to outer appearance, then inorder to escape uncertainty and use this concept in the lattersignificance—in which it is taken in the proper psychologicalquestion about the reality of our outer intuition—we willdistinguishempirically external objects from thosethat might be called “external” in the transcendentalsense, by directly calling them “things that are to beencountered in space”. (A373)

In the transcendental sense, an object is “outside me”when its existence does not depend (even partly) on my representationsof it. The empirical sense of “outside me” depends uponthe distinction between outer and inner sense. Inner sense is thesensible intuition of my inner states (which are themselvesappearances); time is the form of inner sense, meaning that all thestates we intuit in inner sense are temporally ordered. Outer sense isthe sensible intuition of objects that are not my inner states; spaceis the form of outer sense. In the empirical sense,“outer” simply refers to objects of outer sense, objectsin space. Transcendental idealism is the view that objects in spaceare “outer” in the empirical sense but not in thetranscendental sense. Things in themselves are transcendentally“outer” but appearances are not.

1.2 The Empirical Thing in Itself

Just as Kant distinguishes a transcendental from an empirical sense of“outer” he also distinguishes a transcendental version ofthe appearance/thing in itself distinction (the distinction we havebeen concerned with up to now) from an empirical version of thatdistinction. The key text here is A45–46/B62–63, which forreasons of brevity will not be quoted in full (cf. the discussion ofthe rose at A29–30/B45, as well as A257/B313).

In the empirical case, the distinction seems to be between thephysical properties of an object and the sensory qualities it presentsto differently situated human observers. This requires distinguishingbetween what is “valid for every human sense in general”and what “pertains to [objects] only contingently because [of]… a particular situation or organization of this or thatsense” (A45/B62). The distinction seems to be that someproperties of objects are represented in experience just in virtue ofthea priori forms of experience, and thus haveinter-subjective validity for all cognitive subjects, while someproperties depend upon the particular constitution of our sense organs(cf. A226/B273). The “empirical thing in itself” is theempirical objectqua bearer of the former set of properties,while the “empirical appearance” is the empirical objectqua bearer of all of its properties, including the latter.For instance, the empirical “rainbow in itself” is acollection of water droplets with particular sizes and shapes andspatial relations, while the empirical “rainbowappearance” is the colorful band we see in the sky.^[5]

For our purposes, the importance of this distinction is two-fold.Firstly, the (transcendental) distinction is not the ordinarydistinction between how objects appear to us in sense perception andthe properties they actually have. Kantian appearances are not theobjects of ordinary sense perception, for Kant holds that appearancesin themselves (things in themselves, in the empirical sense)lack sensory qualities like color, taste, texture, etc. In scientificresearch, we may discover how appearances arein themselves(in the empirical sense) but in so doing all we discover is moreappearance (in the transcendental sense); scientific investigationinto the ultimate constituents or causal determinants of objects onlyreveals more appearance, not things in themselves. Secondly, there isan appearance/reality distinctionat the level ofappearances. This provides a further sense in which Kant is an“empirical realist”: appearances in themselves haveproperties quite different than they seem to have in senseperception.

Kant’s empirical realism—not in his technical sense, but in thebroader sense that he accepts an appearance/reality distinction at thelevel of appearances (see Abela 2002)—is further deepened by hisscientific realism: he accepts the existence of unobservable entitiesposited by our best scientific theories and holds that these entitiesare appearances (because they are in space).^[6] Earlier, we saw texts whoseprima facie meaning is thatappearances exist, at least partly, in virtue of the contents of ourrepresentations of them. But it is clear that Kant cannot hold thatthe existence of an object in space is grounded in our directperception of that object, for that would be incompatible with theexistence of unperceived spatial objects.

2. The Feder-Garve Review and Kant’s Replies

The first published review of theCritique of Pure Reason, byFeder and Garve (1782), accuses Kant of holding a basically Berkeleyanphenomenalist conception of objects in space. Feder and Garve were notthe only ones to read Kant as a phenomenalist. The phenomenalistreading was so widespread and influential that it became the defaultinterpretation for generations after the publication of theCritique. In fact, many of the key figures in Germanphilosophy in 1781 and after (e.g., Mendelssohn, Eberhard, Hamann,Jacobi, Fichte, Schelling) take the phenomenalist or“subjectivist” reading of Kant for granted and think thisis precisely why Kant must be “overcome”. The assumptionthat Kant is a subjectivist about appearances is a major impetus inthe development of German idealism.^[7]

However, the phenomenalist reading of transcendental idealism has beenchallenged on many fronts, both as an interpretation of Kant and(often on the assumption that it is Kant’s view) on its ownphilosophical merits. This section explores the origin of thephenomenalist reading in the Feder-Garve review and its basis in thetext of theCritique. The next section provides some reasonsto think that the phenomenalist reading is more defensible as aninterpretation of Kant than is sometimes appreciated. Section 3.4explores influential objections by Kant’s contemporaries totranscendental idealism, on the assumption that the phenomenalistinterpretation of that doctrine is correct, which were later taken upas criticisms of the phenomenalist interpretation itself.Section 4 introduces a theme explored in greater detail in later sections: thedevelopment of non-phenomenalist interpretations of Kant’stranscendental idealism.

2.1 The Feder-Garve review

Although it is uncharitable and, on some points, simply mistaken, thefirst published review of theCritique, originally written byChristian Garve and then substantially revised, and shortened, byJ.G.H. Feder, raised an issue that has been discussed ever since.^[8] The Göttingen, or “Feder-Garve” review, as it is nowknown, claims that Kantian “transcendental” idealism isjust idealism of a familiar Berkeleyan or phenomenalist variety(Sassen 2000: 53).

First of all, it should be noted that the Feder-Garve view, while notexactly an exercise in interpretive charity, is not without a basis inclaiming that there is a deep similarity between Berkeley and theCritique (this point is brought out well in Beiser 2002:49–52). First of all, Kant repeatedly claims that empiricalobjectsare representations. For instance, in the“Transcendental Aesthetic” he writes that “what wecall outer objects are nothing other than mere representations of oursensibility” (A30/B45) and in the “FourthParalogism” he writes: “external objects (bodies) aremerely appearances, hence also nothing other than a species of myrepresentations” (A370; see also A30/B45, A104 and A375n, A490,A498, A563). Since “representation” [Vorstellung]is Kant’s term for what Berkeley calls “ideas”, this seemsat least perilously close to the Berkeleyan view that bodies arecollections of ideas. Secondly, the A Edition is full of passages thatcan easily suggest a phenomenalist view of objects in space, such as:

Why do we have need of a doctrine of the soul grounded merely on purerational principles? Without doubt chiefly with the intent of securingour thinking Self from the danger of materialism. But this is achievedby the rational concept of our thinking Self that we have given. Foraccording to it, so little fear remains that if one took matter awaythen all thinking and even the existence of thinking beings would beabolished, that it rather shows clearly that if I were to take awaythe thinking subject, the whole corporeal world would have todisappear, as this is nothing but the appearance in the sensibility ofour subject and one mode of its representations. (A383; cf. A374n,A490–1/B518–9, A520/B492–A521/B493, A494/B522)

On one plausible reading of these passages, Kant is claiming that allthere is for objects in space to exist is for us to have experiencesas of objects in space. Consequently, if we did not exist, or did nothave such experiences, these objects would not exist. The Feder-Garveinterpretation of transcendental idealism is not without some merit.^[9]

2.2 Varieties of Phenomenalism

Phenomenalism can mean many things, and later we will explore thesemeanings in detail, but for now it is worth distinguishing at leastthree different things we might mean by phenomenalism:

(1): Objects in spaceare identical to (unified collections of) our representations.^[10]
(2): Objects in spaceexist solely in virtue of the contents of our representations of them.They possess all of their properties solely in virtue of the contentsof those representations.
(3): Objects in spaceexist partly in virtue of the contents of our representations of them.They possess their “core physical properties” solely invirtue of the contents of those representations.

By “core physical properties” I mean the properties thatappearance have “in themselves” according to Kant,roughly, Lockean primary qualities (see Locke,Essay concerningHuman Understanding, book II, chapter VIII). Feder-Garve accuseKant of holding (1), which I will call “identityphenomenalism”. But even if he did not hold that extreme view,he might hold one of the weaker views listed here. Claim (2) is aquite strong form of phenomenalism, for it entails that, in somesense, all there is to objects is our representations of them,although they are not literally identical to those representation. Iwill call this “strong phenomenalism”. The exact meaningof Berkeley’s own views about bodies is unclear, and not the subjectof this entry. But it is not implausible to read Berkeley as holding(2). However, claim (3), while very controversial and (arguably)extremely counter-intuitive, is weaker. It allows that there may bemore to the existence of objects in space than our representing them,and it allows that there may be aspects or properties of objects thatthey possess independently of how we represent them. I will call it“qualified phenomenalism”. In discussing the debate aboutKant’s alleged phenomenalism, and Kant’s own responses to theFeder-Garve review, it will help to have these distinctions inmind.

2.3 Kant Strikes Back

Kant’s was apoplectic that Feder and Garve had, apparently, not madeany serious attempt to even understand theCritique, or topresent its contents accurately to their readers. He penned a responseto the review, published as an appendix to theProlegomena.In the appendix, and in the text of theProlegomena itself,Kant explains what he sees as clear differences between his own viewand Berkeley’s. First, Kant identifies idealism as the doctrinethat

all cognition through the senses and experience is nothing but sheerillusion, and there is truth only in the ideas of pure understandingand reason (Ak. 4:374)

and points out that, in this sense, his view is not idealism at allbecause theCritique consistently maintains that bodies existin space and that we have immediate (non-inferential) knowledge of them.^[11]Secondly, Kant points out that his idealism is merelyformal: he has argued only that theform of objectsis due to our minds, not theirmatter (cf. Kant’s Dec. 4 1792letter to J.S. Beck (Ak. 11:395)). While the form-matter distinctionin Kant’s philosophy is a complex matter in its own right, Kant’spoint seems to be that thematter of experience, the sensorycontent that is perceptually and conceptually structured by space andtime, and the categories, respectively, is not generated by the minditself, but is produced in our minds through affection bymind-independent objects, things in themselves (see, however,section 3.4 for some reasons to be suspicious of the doctrine of “noumenalaffection”). As he would write several years later in responseto Eberhard, theCritique

posits this ground of the matter of sensory representations not onceagain in things, as objects of the senses, but in somethingsuper-sensible, whichgrounds the latter, and of which we canhave no cognition. (Discovery, Ak. 8:205)

Thus, Kant can claim that only the form of experience ismind-dependent, not its matter; the matter of experience depends upona source outside of the mind.^[12]

However, Kant’s attempts to distance himself from Berkeley may not cutas deep as he seems to think. Regarding the first point, Kant’sdefinition of idealism in the Appendix (quoted above) does not applyto Berkeley. Nor is it clear that his definition in the body of theProlegomena does either:

the claim that there are none other than thinking beings; the otherthings that we believe we perceive in intuition are onlyrepresentations in thinking beings, to which in fact no objectexisting outside these beings corresponds. (Ak. 4:289)

One of the main points of Berkeley’s philosophical project is todefend the existence of bodies in space, while denying what he takesto be a philosophical misinterpretation of what this existence amountsto: the existence of non-thinking substances. Berkeley does not denythat bodies exist; he claims that bodies cannot exist without minds toperceive them, something that Kant himself also seems to accept (seethe texts quoted in the previous section). In fact, Berkeleyconstantly contends that his theory is the only way to avoid what Kantcalls “problematic” idealism: we do not know whetherbodies exist (Treatise on the Principles of Human Knowledge,Part I, § 1, 6, 18, 20, 22–24, 34–38). That Kantwould describe Berkeley as an idealist in this sense (what heelsewhere designates a “dogmatic idealist”) raises thesuspicion that has misread Berkeley.^[13] Since the misinterpretation of Berkeley as holding that senseperception is illusory and that bodies do not exist was widespread inGermany in the eighteenth-century (again, see Beiser 2002), it isquite possible that Kant shares it. It may be that Kant is moresimilar to Berkeley than he realizes because he is not familiar withBerkeley’s actual theory.

Nor does another point Kant makes—that Kant’s idealism concernsmerely the form and not the matter of experience—constitute aclear difference from Berkeley. Berkeley does not claim that humanspirits are the causes of their own ideas; he claims that God acts onhuman spirits, causing us to perceive an internally andinter-subjectively consistent world of ideas. Since Kant’s officialdoctrine in theCritique seems to require agnosticism aboutthe ultimate nature of the things in themselves that causally affectus in experience, it is compatible with what he says that the noumenalcause of experience is God himself.

Kant’s argument might be that the matter of experience (its sensorycontent) depends upon how our sensibility is affected bymind-independent objects, things in themselves, while the form ofexperience is determined by our minds alone. Consequently, experienceitself requires the existence of objects “outside” (in thetranscendental sense) the mind. But this would show, at most, thatKant is not a strong phenomenalist. It does not undercut theinterpretation of him as a qualified phenomenalist. Nor does itsucceed in clearly differentiating him from Berkeley. (See thesupplementary article:Kant’s Attempts to Distance Himself from Berkeley.) This, of course, does not settle the issue; it may be that Kantianappearances are quite different than bodies, as Berkeley, or even thequalified phenomenalist, conceive them (for important discussions oftranscendental idealism in theProlegomena see Ak.4:283–4, 286, 289–294, 314–315, 320).

2.4 Changes in the B Edition

Kant extensively revised certain sections of theCritique forthe second edition (B), published in 1787. It is widely accepted thata main consideration in these revisions was to avoid themisunderstanding of his view that had led to the Feder-Garve review.However, some scholars think that, on this point, there is adifference in doctrine between the A and B editions: made aware of theproblematic Berkeleyan consequences of the first edition, Kantendeavored to develop a more realistic view in the B Edition.^[14] Other scholars think the difference is largely a matter ofpresentation: in the B edition, Kant highlights the more realisticaspects of his view and downplays its phenomenalistic sides, but theview is basically the same (e.g., Allison 2004). The rest of thissection considers the main textual changes from 1781 to 1787 andconsiders what implications they have for the interpretation of Kant’sidealism. Since Kant made no significant changes past the Paralogismschapter, I will not cite sections that did not undergo substantialrevision as evidence; it may be that Kant would have significantlychanged those sections if he had gotten there (on the general topic ofthe changes from the A to the B edition, see Erdmann 1878).

Kant did, however, make one relatively minor alteration in the latersections (in the “Antinomies”, to be specific) that isrelevant to our discussion. In the wake of the Feder-Garve review, Kantevidently felt that “transcendental” idealism may havebeen a poor choice of name.^[15] In the B Edition Kant adds a footnote to his definition oftranscendental idealism at A491/519 (quoted earlier) to remark thatperhaps he should have called his position “critical idealism”.^[16] The section Kant most heavily revised for the B Edition is the“Transcendental Deduction”, but I do not have space hereto discuss the complex argument of that section, or the differencesbetween the A “Deduction” and the B“Deduction”.

2.4.1 Objects as representations

As mentioned earlier, one of the main sources, both in the eighteenthcentury and today, for the phenomenalist reading of Kant is Kant’stendency toidentify empirical objects with representations.But Kant continues to do this in the B Edition, not only in sectionsthat were heavily revised for the B Edition^[17] but even in passages that were added to the B Edition (e.g.,B164).

2.4.2 Preface

The B Preface contains several passages, which some scholars take tobe inconsistent with the phenomenalist reading. They are discussedbelow insection 4.1.

2.4.3 Transcendental Aesthetic

The main addition to the B “Transcendental Aesthetic” isseveral pages (B66–69) at the end of the section, which includesthis discussion, a clear reference to the Feder-Garve review:

If I say: in space and time intuition represents both outer objects aswell as the self-intuition of the mind as each affects our senses,i.e., as itappears, that is not to say that theseobjects would be a mereillusion. […] Thus Ido not say that objects merelyseem to exist outsideme or that my soul onlyseems to be given if I assertthat the quality of space […] lies in my kind of intuition andnot in these objects in themselves. It would be my own fault if I madethat which I should count as appearance [Erscheinung] intomere illusion [bloßen Schein]. (B70–1)

This reiterates a theme found in the A edition and in theProlegomena: transcendental idealism does not entail thatobjects in space are illusions. Later in the paragraph Kant arguesthat, if we assume that if space and time must be “infinitesubstances”, if they exist at all, then we cannot blame Berkeleyfor concluding that space, time, and bodies are mere illusions;empirical idealism is the right conclusion to draw from transcendentalrealism, according to Kant. While Kant is correct in representingBerkeley later in this paragraph as reacting against the Newtonianview of space and time as “absolute” entities, he is wrongto characterize Berkeley as concluding that bodies are mere illusions,so Kant’s dissatisfaction with Berkeley’s own view is not evidencethat he does not have a some variety of phenomenalist view of objectsin space. The B “Transcendental Aesthetic” adds no newevidence against the phenomenalist reading.

2.4.4 Paralogisms

One main source of the phenomenalist reading is the A Edition“Fourth Paralogism”, in which Kant refutes the“Cartesian” view that our inner states are immediatelyknown while the existence of outer objects can only be known mediatelyby inference from our inner states. The Paralogisms section wasentirely re-written in the B Edition, and none of the four BParalogisms correspond precisely to the fourth A Paralogism. The AEdition “Fourth Paralogoism” is the source of many of thepassages quoted above, and, historically, an important source for thephenomenalist interpretation. The fact that it was, effectively,removed in the B Edition has led many scholars to reject thephenomenalist interpretation, at least with respect to the B Edition(with some averring that he changed his mind from the A to the B Edition).^[18] A version of the A Paralogism argument that self-consciousnessrequires knowledge of objects in space reappears as the“Refutation of Idealism”, added in the B Edition.

2.4.5 Refutation of Idealism

Given its brevity, the “Refutation of Idealism”, added tothe “Postulates of empirical thinking in general” in the BEdition, is, line for line, one of the most thoroughly commented uponpassages in all of Kant’s writings.^[19] Kant’s argument, very briefly, is that the existence of objects inspace outside me (“empirically external” objects) is acondition on the possibility of my being conscious of the determinatetemporal relations of my inner states. Consequently, it is impossibleto be a self-conscious subject without there existing objects in spaceoutside of me, and in being conscious of the temporal relations of myinner states I am immediately conscious of the existence of these objects.^[20] The problem of “problematic idealism”—how can Iinfer the existence of objects outside of me on the basis of myimmediate knowledge of my inner states?—is based on a falsepremise.

Nothing about this conclusion, or how Kant argues for it, isprimafacie incompatible with a qualified phenomenalist reading oftranscendental idealism, or even a strong phenomenalist one.^[21] It may be incompatible with “identity” phenomenalism,since Kant argues that self-consciousness requires the existence ofpermanent objects in space, yet there is no permanent representationin the mind (B278). If objects just are representations, it followsthat none of them are permanent.^[22] At B274 Kant makes it clear that the “idealism” that heintends to refute is idealism as he defined it in theProlegomena and the “Fourth A Paralogism”: theclaim that objects in space do not exist (dogmatic idealism) or atleast that we do not know whether they exist (problematic idealism).The sense of idealism that is at issue in the phenomenalistreading—empirical objects exist, and exist in virtue of thecontents of experience—is not, apparently, addressed here. On anextreme phenomenalist reading, all there is to the existence ofempirical objects in space is our having appropriately unifiedexperiences of them. The phenomenalist can interpret Kant’s argumentin the “Refutation” as an argument that consciousness ofthe temporal relations of my inner states requires that these innerstates constitute appropriately unified experiences. Consequently,self-consciousness requires the existence of objects in space(spatially) outside me.^[23]^,^[24]

2.4.6 General note to the principles

In the B Edition Kant added a “General Note” to the“Principles of Experience”, which some have read as rulingout the phenomenalist reading, especially the long passage from B291to 294, from which I quote an excerpt:

This entire remark is of great importance, not only in order toconfirm our preceding refutation of idealism, but, even more, when wecome to talk ofself-cognition form mere innerconsciousness and the determination of our nature without theassistance of outer empirical intuition, to indicate to us the limitsof the possibility of such a cognition. (B293–4)

Once again, this is a case of Kant emphasizing that his view is notidealistin the specific sense of idealism we have seen sofar—denying either that objects exist in space or that wecan know that they do. His point is that even understanding our mostbasica priori concepts, the categories, requires applyingthem to outer objects in space. The remark about“self-cognition” at the end is a reminder that innerawareness is dependent upon outer experience; it does not addresswhether empirical objects exist (partly or wholly) in virtue of thecontents of experience.

2.4.7 Phenomena and noumena

Kant extensively revised the section entitled “On the grounds ofthe distinction of all objects into phenomena and noumena” inthe B Edition. However, since that section concerns the Kantian notionof “noumena” I will reserve discussion of ituntilsection 6, which is devoted to that notion, its relation to the “thing initself”, and the related notion of the “transcendentalobject”.

3. Kant as a Phenomenalist

So far, we have seen theprima facie evidence for thephenomenalist interpretation of Kant, made famous by Feder-Garve, andKant’s own attempts to distance himself from their accusations.However, we also distinguished three different kinds of phenomenalism:identity phenomenalism, strong phenomenalism, and qualifiedphenomenalism. This section explores the interpretation of Kant asqualified phenomenalist, and explores how a defender of this interpretation might answersome of the standard objections to the phenomenalist reading.

3.1 Appearances = representations?

While the identity phenomenalist interpretation has found fewdefenders among contemporary readers (Guyer 1987: 333–336 is anotable exception; for critical discussion, see Allison 2004:8–9), it is worth asking why exactly we should reject theprima facie meaning of the numerous passages in which Kantequates appearances with representations.

Perhaps the best reason to reject the identity phenomenalistinterpretation is that it is incompatible with many of the very textsthat are used to motivate it (there is also the lingering problem ofwhether it is compatible with the “Refutation ofIdealism”; seesection 2.4. and part IV of Guyer 1987). In many of the texts in which Kantidentifies appearances with (a species of) representations, he alsoclaims that representations are representationsofappearances, i.e., that representations are representations ofobjects, appearances. For instance,

[…] external objects (bodies) are merely appearances, hencealso nothing other than a species of my representations, whose objectsare something only through these representations, but are nothingseparated from them. (A370–1)
everything intuited in space or in time, hence all objects of anexperience possible for us, are nothing but appearances, i.e., mererepresentations, which, as they are represented, as extended beings orseries of alterations, have outside our thoughts no existence groundedin itself (A490–1/B518–9; Allison (2004: 36) attempts toexplain away the apparently phenomenalist implications of thispassage)

In both passages, Kant describes appearances as representations butalso asobjects of representation. If this is correct, thenKant thinks that the sense in which an appearanceis arepresentation is compatible with it being the object of arepresentation. For instance, the sense in which this table“is” a representation is compatible with it being theobject of my perceptionof it. Assuming that therepresentations that empirical objects “are” are notalways self-representational (e.g., the table is not identical to atable-ish visual perception that also represents itself), it followsthat the objects cannot be identical to our representations of them.For instance, my visual perception of this table cannotbethis table, because my visual perception does not (presumably)represent itself. To make the identity phenomenalist view consistentwith the very texts that motivate it, we need to “double”our representations: a visual perception of the table and then therepresentation that the table is. But what could that representationbe? It must be present when and only when the table exists (becausethey are identical), and my perception of the table must beintentionally directedat it. While this is not conclusive,it is evidence that the identity phenomenalist interpretation shouldbe abandoned.

Is there any way to free Kant from the apparent consequences of histendency to identify appearances with representations of them? Onestandard strategy is to say that Kant is simply being sloppy: he meansthat appearances are the objects of our representations, not that theyliterally are those representations.^[25] However, the passages in question occur throughout theCritique, in both editions, and they remain after Feder-Garvepointed out their apparently phenomenalist implications. On the otherhand, their persistence in the B Edition suggests that they do not,and never were intended to, commit Kant to a form of identityphenomenalism. How could Kant claim Feder-Garve had misunderstood himif he had identified appearances with representations? This suggeststhat another reading is possible, but does not tell us what it is.

One strategy would be to claim that Kant does not mean the“is” of identity, but the “is” of grounding.Sometimes, apparent claims of identity are really claims aboutgrounding relations. For instance, if I say “pain is C-fiberfiring” I might mean the type-identity thesis that the state ofbeing in pain is the state of C-fiber firing. But I might also meanthat all there is to pain is C-fiber firing, that if one is in pain itis in virtue of C-fiber firing, or that C-fiber firing non-causallygrounds the state of being in pain. On this view, in claiming thatappearancesare representations, Kant is claiming that thecontents of representations ground the existence and empiricalproperties of appearances.

But this is not the plain meaning of the relevant passages. At A371Kant claims that appearances are a species (Art) ofrepresentations; while “is” can be interpreted in a numberof ways (e.g., the “is” of constitution), it is hard tointerpret “As are a species ofBs” inany other way than: everyA is aB, which meanseveryA is identical to aB (namely, itself). Whilethere may be something to the “grounding” interpretationof these passages, there are good reasons to think these texts havenot been explained (or explained away).

A third alternative, proposed by Wilfred Sellars, and which mayultimately face the same problem, relies on the Cartesian distinctionbetween the formal and objective reality of representations (inCartesian terminology, ideas).^[26] The objective reality of an idea is the representational character ofthe idea, its character as a representation with a certain content.Consequently, we can talk about the object of an idea without assumingthat there is an object “external” to the idea; to talk ofthe “internal” object of the idea is just to talk aboutthat idea’s objective reality. For instance, we can coherently talkabout God without presupposing that God exists “outside”our idea of him; this God-talk is to be understood as talk about ouridea of God in its objective realty, i.e., to talk about the contentof our God-idea. Translating this back into Kant, we might take hisclaims that appearances are representations as claims to the effectthat appearances are representationsconsidered in their objectivereality, or, in other words, that talking about appearances,objects of representations, is just talking about representations andtheir contents.

There are at least two problems with this strategy, however. For one,it is arguably no less a distortion of the plain letter of the textthan the other interpretations. If Kant meant that appearances arerepresentationsconsidered with respect to their objectivereality why didn’t he simply say that, rather than stating thattheyare a species of representations? Secondly, it is farfrom clear that, on Kant’s view,talk about appearances isequivalent totalk about the objective reality ofrepresentations. Kant may not be attempting a semantic analysis ofappearances in terms of representations. To many readers, it hasseemed more plausible to read Kant as claiming that appearances aregrounded (non-semantically) in representations and theirobjective reality (content). So this proposal may collapse into theprevious one.

3.2 Qualified phenomenalism

Kant repeatedly claims that our representations alone do not groundthe existence of their objects. At A92/B125 he writes that“representation in itself does not produce its objects in so faras existence is concerned” and in a 1792 letter to J.S. Beck hedismissed the Feder-Garve interpretation with one line:

I speak of ideality in respect of theform of representation,while they construe it as ideality in respect of thematter,i.e., ideality of the object and its existence. (Ak. 11:395)

The first passage could be taken to mean that the existence ofempirical objects is notwholly grounded in the contents ofour experience; something else must be added. The second passage couldbe taken to mean that Feder and Garve misattributed to him theopposite view: that all there is to the existence of an object inspace is our having mental states with a certain content. But all thisshows is thatstrong phenomenalism is not Kant’s view. Itleaves open the possibility that he acceptsqualifiedphenomenalism: the existence of objects in space is groundedpartially, and their core physical properties are grounded wholly, inthe contents of our representations of them.

The first question to be answered is, what, in addition to thecontents of our representations, grounds the existence of empiricalobjects? The natural answer, for the qualified phenomenalist, is thatthere must be things in themselves that appear as these objects. Kantrepeatedly insists that it is a conceptual truth that appearances areappearances of something that is not itself an appearance, a thing initself (e.g., A251–2, Bxxvi–xxvii, B306, B307, and Ak.4:314–5). On the qualified phenomenalist reading, this meansthat the existence of an appearance requires (a) a representation ofan object, and (b) a thing in itself that appears as that object. Afully developed qualified phenomenalist reading would require sayingprecisely what it means for a thing in itself to appear as anempirical object (an object of experience), but for reasons of spaceonly a sketch of an answer can be given here. At the minimum, thequalified phenomenalist should require that the thing in itselfcausally affect the experiencing subject, and that the sensory contentthus produced be involved in the experience of the object. Somescholars have suggested that the properties of appearances arestructurally isomorphic to the properties of things in themselves, butI will not further pursue that idea here (e.g., Findlay 1981:92–93; see also Van Cleve 1999: 155–162).

The qualified phenomenalist also owes us an answer to the question,which are the representations whose content partly grounds theexistence of empirical objects and wholly grounds their core physicalproperties? The natural answer is “experience”, so thequalified phenomenalist owes us an interpretation of what Kant meansby “experience”, what its content is, and how it grounds(partly) the existence and (wholly) empirical properties of appearances.^[27] We have already seen that, for familiar reasons, Kant cannot groundthe existence of empirical objects in our mere perceptions of them:sometimes we misperceive objects, objects exist while unperceived, andthere are objects we cannot ever directly perceive.

There have been few worked-out phenomenalist interpretations of Kantin the secondary literature, so in what follows I present an outlineof one such reading. I do this so that the reader has some moredeterminate idea of what a qualified phenomenalist reading might looklike and why (section 3.3) some of the classic objections to phenomenalist interpretations maybe less devastating than they are sometimes presented. I do not wantto give the impression that this is the only plausible phenomenalistreading of Kant.

The qualified phenomenalist grounds the existence of objects (partly)and their core physical properties (wholly) in the content ofexperience. But this requires a conception of experience on which itis not identical to any individual subject’s perceptual episodes;otherwise, objects will have contradictory properties if, forinstance, I see the tower as round and you see it as square. Kantdistinguishes experience from perception in the A“Deduction”, writing:

There is onlyone experience, in which allperceptions are represented as in thoroughgoing and lawlike connection[…] If one speaks of different experiences, they are only somany perceptions insofar as they belong to one and the same universalexperience. (A110).

In this sense of experience (“universal experience”) thereis only one experience. It may also be that, inter-subjectively, thereis only one universal experience as well: my perceptions and yourperceptions are only “experiences” to the extent that theycohere with the one universal experience. Kant, in this passage, doesnot tell us much about what universal experience is, or what itscontents are. He does tell us that it is composed from perceptions,that it has ana priori form (space, time, and categories),and that the perceptions that constitute it are in“thoroughgoing and lawlike connection”.

Elsewhere, he sheds further light on the coherence relation thatdefines universal experience:

In space and time, however, the empirical truth of appearances issatisfactorily secured, and sufficiently distinguished from itskinship with dreams, if both are correctly and thoroughly connected upaccording to empirical laws in one experience. Accordingly, theobjects of experience are never given in themselves, but only inexperience, and they do not exist at all outside it. (A493/B521)

PerceptionP_n coheres withperceptionsP₁throughP_n−1 to the extent that thecausal laws observed inP₁throughP_n−1 are observed inP_n. This gives us reason to exclude hallucinatory perceptionsfrom universal experience: hallucinatory perceptions involve apparentviolations of the causal laws that are observed to hold in our“waking” perceptions, so they do not cohere with thoseother perceptions.

We knowa priori something very general about the form ofuniversal experience, of course: it will be spatiotemporal and theprinciples of experience (applications of the categories) will hold init. But that does not determine the determinatea posterioricontent of universal experience, and the idea of a qualifiedphenomenalist analysis of empirical objects is to hold that theirexistence and empirical properties are (partly and wholly,respectively) grounded in that fully determinatea posterioricontent. So we might begin with the following analysis:

(Experience) Universal experience consists in the largestinternally coherent subset of perceptions that obeys the principles ofexperience. A subset of perceptions is internally coherent to thedegree to which causal regularities hold among its contents.

On a qualified phenomenalist reading of Kant, this might be taken asthe set of representations whose content grounds objects. However,there are at least two problems with this analysis of universalexperience:

(i): Unperceivedobjects. Kant holds that there are spatiotemporal objects wecannot perceive. This by itself would pose a problem for the proposeddefinition of universal experience, since, on the qualifiedphenomenalist view, that definition entails that there cannot beunperceived spatiotemporal objects. But Kant further claims that wecanexperience unperceivable objects through perceiving theireffects and inferring their existence from causal laws. So thedefinition of universal experience needs to be refined (A226/B273;Langton (1998: 186–190).
(ii): Secondaryqualities. As we discussed above in the section on Kant’sempirical realism, Kant distinguishes between the propertiesspatiotemporal objects actually have “in themselves” andthose they merely appear to have in sense perception. He has abasically Lockean distinction between primary and secondary qualitiesat the empirical level. Since we perceive objects as having secondaryqualities, the definition of universal experience given above,combined with the qualified phenomenalist analysis, entails thatempirical objects have secondary qualities. We need to further refineour definition of universal experience to eliminate secondaryqualities from the empirical properties of objects.

We need to refine the conception of experience so as to includeunperceived objects and exclude secondary qualities. This might pushus towards a more “scientistic” conception of universalexperience, on which experience is something like the ideal scientifictheory of objects in space and time.^[28] The form of that theory isa priori determinable from theforms of experience: it will represent persisting substances in a 3-DEuclidean space obeying universal causal laws and in simultaneousmutual interaction. However, the determinatea posterioricontent of that theory will be grounded in the perceptions subjectsactually have.

Here is a sketch of a conception of universal experience that thequalified phenomenalist might accept:

(Experience) Universal experience is the maximally unifiedand lawful representation of objects in space and time that iscompatible with thea priori forms of experience andjustified by the totality of subjects’ perceptual states, or theconjunction of such representations if there is no unique such representation.^[29]

To fully develop such a view, a lot more would have to be said aboutexactly how the content of experience is grounded in, and justifiedby, the contents of subjects’ perceptual states, but this glossis enough to give us a sense of what a developed phenomenalist readingof Kant might look like.

3.3 Criticisms of Phenomenalist Readings

Since the Feder-Garve objection to Kant has been around almost as longas theCritique itself, many objections to broadlyphenomenalist readings of Kant’s idealism have accumulated. Perhapsthe most comprehensive list of such objections is given by Allais(2004). They include:

“Kant’s claim that his notion of appearanceimplies that there is something that appears”. I have alreadyexplained how the qualified phenomenalist can accommodate thispoint.
“Empirically real objects and the space theyinhabit are public”. Allais seems to assume that, on aphenomenalist analysis of objects in space, objects are“private”, meaning the objects each subject perceives areconstituted by sense data of that subject, which, by definition,cannot be perceived by other subjects. But the qualified phenomenalistconception of universal experience sketched above is explicitly“non-private” in this sense; it is based on theperceptions ofall subjects.
“Kant’s distinction between primary and secondaryqualities”. However, the qualified phenomenalist can claim thatwhile our perceptions represent objects as having secondary qualities,the best scientific theory justified by the totality of thoseperceptions (universal experience) does not represent them as havingthose properties, because there is a better theory available: objectsdo not possess such properties but do possess powers to cause us toperceive them as having such properties. There is, in principle,no barrier to a qualified phenomenalist allowing the distinction betweenprimary and secondary qualities.
“Kant’s realism about the unobservable entities oftheoretical science”. Kant is a scientific realist, in that heaccepts the existence of unobservable entities posited by our bestphysical theories (magnetic matter, Newtonian “lamellae”).Allais thinks this is incompatible with a phenomenalist reading, butit is compatible with the conception of universal experience developedin the previous section. If universal experience has the content ofthe scientific theory best justified by our perceptions, thenuniversal experience can represent unobservable (=unperceivable)objects (cf. Allison (2004: 46)) who also objects that phenomenalism isincompatible with Kant’s empirical realism).
“Empirically real objects exist through time andunperceived, and are in causal relations”. The fact thatempirically real objects exist through time while unperceived might bethought to pose a problem for phenomenalism, although it should beremembered that Berkeley (at least on some readings) is aphenomenalist and yet accepts that objects exist while unperceived(although he denies that they stand in causal relations). So it isn’tclear why Allais think this is incompatible with phenomenalism. And itclearly is compatible with the conception of universal experiencedeveloped in the previous section: experience represents objects asexisting through time and unperceived, because a theory thatrepresents them as existing only when perceived would be far lessunified and lawful.
“We do not know what ideas are in themselves”.Allais’s idea seems to be that the phenomenalist is committed togrounding empirical objects not in “empirical ideas”(temporally ordered mental states available in consciousintrospection) but in “noumenal ideas” (the non-temporalstates of the subject in itself). But it is unclear why; thephenomenalist conception of experience developed in the previoussection explicitly grounds thea posteriori content ofuniversal experience in “empirical” ideas, the totality ofsubjects’ perceptions.^[30]

Allais appears to have conflated phenomenalist readings of Kant ingeneral with the “strong” phenomenalism (or even identityphenomenalism) discussed insection 2, and one, moreover, that identifies experience with mereperception.

3.4 The Problem of Things in Themselves

No discussion of Kant’s transcendental idealism would be completewithout a discussion of F.H. Jacobi’s famous objection to thecritique:

without the presupposition of the [thing in itself] I cannot enter the[critical] system, and with that presupposition I cannot remain in it.(Jacobi,Werke, vol. II, p. 304)

Jacobi is referring to a number of quite serious problems for Kant’stranscendental idealist theory. They do not disappear on otherinterpretations, but they are especially serious for the traditionalphenomenalist reading. Unlike the problems we discussed earlier,however, which were specifically problems for the phenomenalistanalysis ofappearances, these problems, as Jacobi indicates,concern the thing in itself, and the relation between things inthemselves and appearances.

3.4.1 The Unknowability of Things in Themselves

Kant is committed to both of the following theses:

(Existence) There are things in themselves.

(Humility) We know nothing about things in themselves.

While these are not, strictly speaking, incompatible, they are intension, forHumility appears to remove any warrant Kantmight have for assertingExistence.

But it gets worse for the traditional view. Kant does not merely claimthat things in themselvesexist, he also asserts that,

(Non-spatiality) Things in themselves are not in space andtime.

(Affection) Things in themselves causally affect us.^[31]

Many of Kant’s early readers concluded that Kant’s philosophy isinconsistent: he claims that we cannot know the very assertions hemakes about things in themselves. Kant’s own theory renders itself unknowable.^[32]

It would be over-hasty to suggest that each of these threeproblems—how to square Humility, with Non-Spatiality, Affection,and Existence—are on a par. Since Non-spatiality makes only anegative claim, it may be easier to make it consistent with Humility.For instance, at B149 Kant writes:

it is not yet a genuine cognition if I merely indicate what theintuition of theobject is not, without being able to saywhat is then contained in it.

This suggests that, while Kant’s usually unqualified statements of ourignorance of things in themselves (they are “not cognized atall” A30/B45), his considered view might be more qualified: weknow nothing of the positive properties of things in themselves.^[33] ButAffection looks especially difficult to square withHumility (see Hogan 2009 and Stang 2013).

3.4.2 Things in themselves as causes

The issue of things in themselvesaffecting us raises anotherproblem for Kant’s theory, for Kant also argues that categories likecause-effect cannot be meaningfully applied to things inthemselves. Without an intuition “[the category] has no sense,and is entirely empty of content” (A239/B298). Since things inthemselves cannot be intuited, categories (includingcause-effect) have no sense or content when applied to thingsin themselves. Jacobi and others thought this was yet anotherinconsistency in Kant’s philosophy: he denies that categories can beapplied to things in themselves, but then he applies the categorycause-effect to them!

However, one has to be careful in interpreting Kant’s denial of“sense” or “meaning” to categories as appliedto things in themselves. It is tempting to read this as meaning thatthe thought of things in themselves falling under categories isliterally nonsense, but there is textual evidence that Kant is makinga weaker point: thinking of things in themselves under the categorieshas nocognitive sense, i.e., in making such judgments we donotcognize anything. For instance,

[…] the categories are not restricted inthinking by the conditions of our sensible intuition,but have an unbounded field, and only thecognitionof objects that we think, the determination of the object, requiresintuition; in the absence of the latter, the thought of the object canstill have its true and useful consequences for theuse of reason […] (B166n)^[34]

We can think of any objects whatsoever using the categories. In fact,this is unavoidable; the categories are the most basic concepts ofobjects in general, so we cannot think about anything whatsoeverwithout using some categories to do so. But in thinking about thethings in themselves using categories we do notthereby (a)know that there are things in themselves falling under the categoriesor (b) even that it ispossible for there to be things inthemselves falling under the categories. The strongest form ofJacobi’s objection—that Kant’s view entails that the categoriescannot be applied, even in thought, to things in themselves—mayrest on a misunderstanding (cf. Van Cleve 1999: 137; Adams 1997:820–1). This still leaves, though, the pressing problem of how,given Kant’s Humility doctrine, he could have any epistemic warrantfor making the various substantive claims he does about things inthemselves (Existence, Non-spatiality, Affection).

3.4.3 The Problem of Affection

Jacobi raises yet another problem about Kant’s theory of experience.He notes Kant’s definition of sensibility as the capacity “toreceive representations through the manner in which we are affected byobjects” (A19/B33) and poses a dilemma: are the objects thataffect our sensibility appearances or things in themselves? Theycannot be things in themselves, Jacobi argues, because that would involveapplying the categories to things in themselves. And they cannot beappearances, because appearances exist in virtue of the veryexperiences they are (allegedly) causing. He concludes that Kant’ssystem is inconsistent (Jacobi,Werke, vol. II,291–310; Fichte raises the same objection in the SecondIntroduction to theWissenschaftslehre; cf. Fichte,Werke I, 488).

We have already discussed the argument of the first horn of Jacobi’sdilemma: we can think but notknow that things in themselvescausally affect us. But what about the second horn? Hans Vaihingerconcisely explains Jacobi’s argument:

Or one understands by affecting objects the objects in space; butsince these are only appearances according to Kant, and thus ourrepresentations, one falls into the contradiction that the sameappearances, which we first have on the basis of affection, should bethe source of that very affection. (Vaihinger 1881: vol. 2, p. 53)

“First” here does not refer to temporal priority, but tometaphysical priority: ifp is true in virtue ofq,thenq is “prior” top. Jacobi andVaihinger assume that appearances exist in virtue of the contents ofour experience of them:

(Trans. Idealism) Ifx is an appearance, thenx exists in virtue of the fact that subjects experiencex.

If we are empirically affected, though, it follows that:

(Empirical affection) For somex,x is oneof the causes of subjects’ experience ofx.

For instance, this computer is one of the causes of my currentexperience of it. But these assumptions are inconsistent if we assumethe following plausible principle:

(Exclusion) Ifx exists in virtue of the fact thatp, thenx cannot be even a partial cause of the factthatp.

Intuitively, this principle says that no object can be even a partialcause of the very fact in virtue of which it exists; if it were, itwould be a partial cause of its own existence. In the context ofKant’s theory of experience, it means that appearances cannot“reach back” and cause the very experiences in virtue ofwhich they exist. From the 1780s until today, many have taken thisproblem to be fatal to Kant’s theory of experience.^[35]

4. The “Dual Aspect” View

Because the phenomenalist interpretation of transcendental idealismheld such sway, not only among Kant’s contemporaries, but forgenerations of German philosophers as well, these problems for thephenomenalist construal of transcendental idealism were taken to beevidence that Kant’s view itself is inconsistent.^[36] In the twentieth century, the phenomenalist (or“Berkeleyan”) interpretation of transcendental idealism isassociated with P.F. Strawson, whose massively influential (1966)argued that, for many of the reasons we have seen, transcendentalidealism was a blunder on Kant’s part (Strawson 1966: 16, 38–42,253–73). However, Strawson claimed, the core arguments of theCritique do not in fact rely on it and can be reconstructedindependently of it.

In the 1960s and 1970s a group of scholars, in some cases in directopposition to Strawson, developed a non-phenomenalist,anti-metaphysical reading of transcendental idealism, the “dualaspect” view.^[37] These scholars took the textbook problems for phenomenalism(especially, the problem of affection) as evidence that this was thewrong interpretation of Kant’s position to begin with. They sought torescue transcendental idealism from what they took to be thephenomenalist misconstrual, defend its philosophical cogency from itsdetractors, and show, contra Strawson, that the central arguments oftheCritique do rely on transcendental idealism. This was asmuch a philosophical defense of Kantian transcendental idealism as itwas an interpretive-exegetical project.

They developed what has become known as the “dual aspect”view. They argue that many of the classic problems for thephenomenalist reading (e.g., affection) arise because it wasmistakenly assumed that appearances and things in themselves aredistinct kinds of objects. They argued instead that theappearance/thing in itself distinction is not an ontologicaldistinction between two kinds of objects, but an adverbial distinctionbetween two different perspectives or stances we can take on one andthe same set of objects: we can consider them as they appear, or asthey are “in themselves”.

4.1 One Object, Not Two

In numerous passages, Kant describes the appearance/thing in itselfdistinction, not as a distinction between two different objects, butas a distinction between two ways of considering one and the sameobject. For instance,

[…] the same objects can be considered from two differentsides,on the one side as objects of the senses andthe understanding for experience, andon the otherside as objects that are merely thought at most for isolatedreason striving beyond the bounds of experience. (Bxviii–Bxix,note)
[…] the reservation must well be noted that even if we cannotcognize these same objects as things in themselves, we are lat leastable tothink of them as things in themselves. (Bxxvi)^[38]

The general characteristic of such passages is that they use the samechain of pronouns to refer both to appearances and things inthemselves. This strongly suggests thatone and the sameobject can be an appearance and a thing in itself, or, to put itanother way, the distinction between appearance and thing in itself isnot a distinction between two or more objects, but a distinctionbetween two different aspects of, or ways of considering, one and thesame object. One and the same object can be consideredas itappears to us in experience, oras it is in itself.Considered in the former way, the object must conform to ourapriori intuitional forms, so it is in space and time. Consideredin the other way, the object may not be in space and time. Some“dual aspect” readers cite the increased frequency of suchpassages in theProlegomena and the B Edition as evidencethat Kant, realizing that his distinction between two aspects ofobjects was being conflated with a distinction between two kinds ofobjects, sought to remedy this interpretation by emphasizing preciselythis point. Prauss (1974) notes that, in most cases, Kant uses theexpression “Dinge [Sachen,Objecte,Gegenstände]an sich selbst” rather thanthe shorter form “Dinge an sich”. He argues that“an sich selbst” functions as an adverb to modifyan implicit attitude verb like “to consider”[betrachten]. He concludes that the dominant use of theseexpressions is as a short-hand for “things considered as theyare in themselves” (Prauss 1974: 14–15).

Different scholars understand this distinction in different ways. Themain difference is between epistemological and metaphysical“dual aspect” interpretations (Allison 2004: 52). On theepistemological reading, the distinction between appearances andthings in themselves is simply a distinction in the standpoint fromwhich we consider them. We can consider objects as objects ofknowledge for discursive spatiotemporal cognizers like us, in whichcase we are considering objects asappearances. Or we canabstract from our particular cognitive conditions and consider objectsmerely as objects for a mind in general, in which case we areconsidering them asthings in themselves. It is crucial tothe epistemological reading that there is no sense in which the“transcendental” perspective on objects asthings inthemselves gets at how objects “are in themselves”.The point of Kant’s transcendental idealism, epistemologicalinterpreters stress, is to get away from the incoherent idea of a“view from nowhere” in which we could know objects as they“really are in themselves”.^[39]

By contrast, metaphysical “dual aspect” interpreters takethe distinction to carry more metaphysical weight. They interpret theappearance/thing in itself distinction as a metaphysical distinctionbetween two different classes of properties had by objects, forinstance, their relational properties and their intrinsic properties.Appearances are objectsqua bearers of “empiricalproperties” (e.g., relational properties) while things inthemselves arethe very same objectsqua bearers of“noumenal” or “non-empirical” properties(e.g., intrinsic properties). The next two sub-sections explore theepistemological interpretation of Henry Allison. The remainder of thesections concerns metaphysical “dual aspect” readings,focusing on the widely discussed interpretation of Langton (1998).

4.2 Allison’s “Epistemic” reading

In modern Kant scholarship, the epistemic reading was first putforward by Gerold Prauss, Henry Allison, and Graham Bird. SinceAllison’s work was the most influential among English languagescholars, and most likely to be known to readers, this discussionwill focus on the interpretation of transcendental idealism in Allison(1983) and the revised and enlarged second edition (2004). Allison’swritings contain several distinct (and not obviously equivalent)formulations of transcendental idealism. This section concentrates onreconstructing what I take to be the “core” of Allison’sreading: his interpretation of appearances and things in themselves,and his reconstruction of the argument for the non-spatiality ofthings in themselves.

The core insight of Kant’s epistemology in general, and histranscendental idealism in particular, according to Allison, is theprinciple that we possess adiscursive intellect. Adiscursive intellect is one that passively receives representations ofparticular objects (intuitions) and then spontaneously subsumes thoseintuited objects under general concepts; consequently, a discursiveintellect must possess a sensory faculty (through which it receivessensory data and intuits individual objects) and a conceptual faculty(through which it forms general concepts and applies them to objects)(A50–1/B74–5). By contrast, an intuitive intellect bringsinto existence its objects merely by representing them, and thus hasno need to receive representations of objects from outside.^[40] But that is not all there is to the discursive nature of ourintellect, Allison argues.^[41] Kant’s key insight is that our sensible faculty has its own epistemicconditions.

An “epistemic condition” is Allison’s term for arepresentation we must apply to objects in order to cognize them(Allison 2004: 11, 14). Space and time are epistemic conditions, asare the categories. IfE is an epistemic condition thennecessarily if we know an objectO, in knowing it werepresent it usingE.^[42] Some of our epistemic conditions follow from the general fact that weare discursive cognizers (the categories) and some follow from themore specific fact that we cognize objects given to us in space andtime. Representing objects using the categories is an epistemiccondition for any discursive intellect, i.e., for any intellect thatmust conceptualize objects given passively in sensory intuition.^[43] So space and time are epistemic conditions of spatiotemporaldiscursive cognition of objects, while the categories are epistemicconditions of discursive cognition of objectsin general. Anydiscursive intellect must conceptualize sensibly intuited objectsusing the categories, whether or not those objects are intuited inspace and time, or some other intuitional forms (Allison 2004:17).

This grounds a distinction between two ways of considering the objectsof our cognition. When we consider objectsqua objects of ourcognition, we consider them as falling under the relevant epistemicconditions. IfE is an epistemic condition of cognition ofobjects, then objects must fall underE (i.e., be accuratelyrepresented byE); otherwise, in representing them withE, I would not be cognizing objects but misrepresenting them.My representation of objects withE would be an illusion, thevery conclusion Kant wants to avoid with respect to space and objectsrepresented in space. This means that ifE is an epistemiccondition of the specific kind of discursive cognition of objects thatwe have, thenE correctly represents those objects. So, ifspace and time are the forms of our intuition, it follows thatempirical objectsqua objects of the kind of discursiveintellect we have, are in space and time. But if we do not considerobjectsqua objects of our specific kind of discursiveintellect, butqua objects of discursive intellect ingeneral, we can no longer assume that our specific intuitionalepistemic condition applies to them. The more general epistemicconditions of all discursive cognition (in Kant’s view, thecategories) still apply to objects under this more abstractperspective, however. So we can say that objectsquaappearing (objects of spatiotemporal discursive cognition) are inspace, butqua things in themselves (objects of discursivecognition in general) they are not in space. This, in a nutshell, isAllison’s reconstruction of the argument for the non-spatiality ofthings in themselves.^[44] While it is legitimate to consider objects as things in themselvesusing the categories, we do not therebycognize them. Thisfollows trivially from the fact that space and time are epistemicconditions for us: without representing objects in space and time, wecan think of objects using the categories, but those thoughts are notcognitions (Allison 2004: 18).

4.3. Problems with the Epistemic reading

Allison’s interpretation has been challenged on a number of points byother scholars. This section discusses a number of suchobjections.

4.3.1 The Triviality Objection

Some scholars object that Allison’s reading of the non-spatialitythesis, and the thesis that things in themselves are uncognizable byus, renders it a tautology, a trivial logical consequence of definitions.^[45] I will represent the definition of “thing in itself” talk(on Allison’s interpretation) as follows:

(1): Things in themselvesareF if and only if objects of discursive cognitionassuch areF.

And the non-spatiality thesis as:

(C): ∴ ~(Thingsin themselves are spatial)

But now the reader can see that to derive (C) from (1) we would need afurther premise:

(2): ~(Objects,considered, as objects of discursive cognition in general, arespatial)

But this claim is not a definition, for it is equivalent to the claimthat the concept of a discursive cognition is more general than theconcept of a spatiotemporal discursive cognition, i.e., that anon-spatial discursive intellect is conceivable. So although thenon-spatiality of things in themselves follows almost immediately fromvery general truths, on Allison’s reconstruction, it is notcorrect to say that it is a tautology, or that it is true bydefinition.

Nor is it true that the uncognizability of things in themselves istrivial, on Allison’s reading. For that principle only follows fromthe claim that there are sensible epistemic conditions, space andtime. And that, on Allison’s reconstruction, is the key insight thatsets Kant apart from both his rationalist and empiricist predecessors.Thus, while Allison’s interpretation makes the argument for thenon-spatiality of things in themselves relativelyeasy, itdoes not render the conclusion trivial.

4.3.2 Epistemic conditions entail realism

Robinson (1994) raises a quite general objection to Allison’s notionof an epistemic condition, namely, an object must satisfy (fall under)a representation if that representation is to constitute an epistemiccondition for that object (Robinson 1994 is a response, mainly, toAllison 1983 and 1987). So in the claim that “objectsqua appearances” or “objectsconsideredwith our epistemic conditions” the qualification“qua appearances” or “considered with ourepistemic conditions” is otiose. If space is an epistemiccondition of outer objects for us then this entails that objects wecognize are in spacesimpliciter. The claim that objects arespatialbecause of orin virtue of space being anepistemic condition for them entailseither that these objectsexist in virtue of our representations of them (which results inphenomenalism)or it entails that they are spatial in virtueof our representing them but would not be spatial otherwise. In thelatter case, we are notcognizing them in representing themas spatial; we aremisrepresenting them (Robinson 1994:420–22).

Allison might reply to this objection by pointing out that itimplicitly assumes that the claimempirical objects are inspace is coherent independently of specifying a perspective onthose objects. In the terminology of Allison (2004) it is committed to“transcendental realism” (see the supplementary entry:Allison on Transcendental Realism and Transcendental Idealism). If this were Allison’s reply to the objection, then it would showthat the coherence of transcendental idealism, on Allison’sreconstruction, rests on the premise that there is no coherent senseto questions about how objects are independent of any perspective onthem. This is important, because it is not always clear that Allison’sreconstruction does depend on this premise, and it is not clear whereKant argues for such a conclusion.

4.3.3 Abstraction

One influential objection focuses on the role that“abstracting” from our spatiotemporal intuition plays inAllison’s reconstruction. Van Cleve puts it somewhat facetiously:

How is it possible for the properties of a thing to be vary accordingto how it is considered? As I sit typing these words, I have shoes onmy feet. But consider me apart from my shoes: so considered, am Ibarefoot? I am inclined to say no; consider me how you will, I am notnow barefoot. (Van Cleve 1999: 8)^[46]

To put the point less facetiously: if the objecto,considered as an object of spatiotemporal cognition, is spatial, thenwhen we ascend to a more general perspective, in which we considero as the object of discursive cognition in general, then weshould not say thato isnon-spatial; we shouldmerelynot judge that it is spatial. To take an example ofGuyer’s, when we consider a job applicant we might want to ignore orabstract from their race or sex; in doing so we would not judge thatthey are race-less or sex-less, but merely refrain from representingthem as having a determinate race or sex.

Allison can interpret Kant’s claim that things in themselves are not spatial in eitherof two ways:

(1): Things in themselvesare non-spatial.
(2): It is not the casethat things in themselves are spatial.

While ordinarily we might take these claims to be equivalent, whentalking about “things in themselves” we can distinguishthem, because “things in themselves” talk is talk aboutobjects from a certain perspective (i.e., considered as objects ofdiscursive intellect in general). In particular, (1) and (2) areequivalent to:

(1*): Objects, consideredas objects of discursive cognition in general, arenon-spatial.
(2*): ~(Objects,considered as objects of discursive cognition in general, arespatial)

Allison’s critics assume that he opts for (1) (and its analysis, (1*))and object, rightly, that this is the wrong conclusion to draw fromthe fact that discursive cognition is a more general notion thanspatiotemporal discursive cognition. (Just as it would be wrong toconclude that the job candidate, considered in abstraction from hissex and race, is sex-less and race-less.) While it is sometimesunclear from Allison’s texts which analysis he opts for, thecharitable reading is that he accepts (2*).

If this is correct, Allison’s reasoning can be reconstructed asfollows:

(3): Things in themselvesareF = objects, considered as objects of discursive intellectin general, areF.
(4): It is conceivablethat there is an object of discursive intellect that is not an objectof spatiotemporal discursive intellect, i.e., spatiotemporaldiscursive intellect is a special case of discursiveintellect.
(5): ∴~(objects, considered as objects of discursive intellect in general,are spatial)
(6): ∴ ~(Thingsin themselves are spatial)

But (6) must be distinguished from:

(7): Things inthemselves are non-spatial.

On this reconstruction of Allison, Kant is committed to (6) but not to(7).

We saw earlier that Allison’s critics assume that he must intend (7)rather than (6). They do so because they think that it is clear fromthe texts that Kant claims (7) and not the weaker (6). But that is notso clear from the texts, for instance:

Space represents no property at all of any things in themselves norany relation of them each other, i.e., no determination of them thatattaches to objects themselves and that would remain even if one wereto abstract from all subjective conditions of intuition. (A26/B42)

Prima facie it is compatible with the letter of these textsthat Kant is claiming (6) rather than (7). Note that (6) is not theclaim that we cannot know, or justifiably assert that things inthemselves are spatial. It is the claim that it isfalse tosay that they arespatial.

The stronger objection to Allison’s view, as reconstructed here, isthat (6) is too weak to be a plausible reconstruction of Kant’snon-spatiality thesis. Given Allison’s understanding of “thingin itself” talk (premise (3)) all that (6) requires is thatthere is some conceivable perspective on objects that is more generalthan the specifically spatiotemporal form of cognition that we have(premise (4)). It does not even require that it is possible that therebe discursive intellects with a non-spatiotemporal form of cognition.All it requires is that the concept of discursive cognition as such ismore general than the concept of spatiotemporal discursive cognition,which, trivially, it is. (6) is compatible with it being impossiblefor there to be non-spatiotemporal discursive cognition because allobjects are necessarily spatiotemporal and hence can only be cognizedspatiotemporally. In other words (6) is compatible with transcendentalrealism about space and time (as Kant defines that term)!

One potential Allisonian response to this objection would be that itimplicitly presupposes that there is a way objects are independentlyof any perspective on them. In particular, the claim that (6) iscompatible with all possible objects being spatial, and thus cannot bea reconstruction of the non-spatiality thesis, begs the question byassuming that that state-of-affairs does not need to relativized to aperspective, e.g., all possible objectsas objects for a certainkind of mind are spatial. Thus, the coherence of Allison’sreconstruction again depends upon the claim that there is no“standpoint-independent” perspective on reality.

4.3.4 Things in themselves as more fundamental than appearances

One major textual hurdle for Allison’s “epistemic” readingof transcendental idealism is the various passages in which Kantdescribes things in themselves as more fundamental, more ontologicallybasic, than appearances, or describes things in themselves as thegrounds of appearances. Allison appears to reverse thisrelation of dependence because things in themselves (objects from therelatively abstract transcendental perspective) are an abstractionfrom appearances (objects from the more determinate empiricalperspective). Ameriks (1992: 334) raises this objection, and Allison(2004: 45) replies to it. Allison does not offer an alternate readingof the relevant texts, but instead points out that, in the case wherethe relative fundamentality of the phenomenal and noumenal is mostimportant to Kant, namely the freedom of the will,^[47] Ameriks’ objection assumes, once again, that there is some factof the matter as to whether we are free or not, and this is to besettled by determining whether we are free at the most fundamentallevel (the noumenal level, on Ameriks’ reading). Once again, thecoherence of Allison’s reading rests on the premise that there is nostandpoint-independent perspective on reality (see the supplementaryentry:Allison on Transcendental Realism and Transcendental Idealism).

4.4 Metaphysical “Dual Aspect” Readings

One prominent strand in recent scholarship on Kant’s transcendentalidealism has been the development of quite sophisticatedinterpretations that try to retain the original insight that theappearance/thing in itself distinction is not a distinction betweentwo different kinds of objects, while abandoning Allison-style“epistemic” readings. These interpretations take thedistinction to be a metaphysical one between two different sets ofproperties had by one and the same set of objects. These metaphysical“dual aspect” interpretations differ in exactly how theyunderstand the distinction between these different sets of properties(see also Allais (2004, 2006, 2007, 2015); Rosefeldt (2007, 2013);McDaniel (ms); and Marshall (2013)).

Perhaps the most influential metaphysical but non-phenomenalistinterpretation of Kant’s idealism has been Langton (1998). Langtonbegins by pointing out that Kant thinks we are genuinely missing outon something in not knowing things in themselves, and this sense of“epistemic loss” is incompatible with Allison’s reading.As we saw in the previous section, “Allisonian humility”is apparently compatible with it being impossible that there arenon-spatiotemporal objects and our forms of intuition being theonly possible such forms. This loses Kant’s sense that we aregenuinely cognitively deprived, that there is something about theworld of which we are irremediably ignorant (Allison responds toLangton’s criticism in 2004: 9–11).

Having rejected Allison’s epistemic reading, Langton goes on todiscuss a familiar tension between two of the central doctrines ofKant’s transcendental idealism:

(Existence) Things in themselves exist.

(Humility) We cannot know anything about things inthemselves.

Langton’s solution to this, one of the oldest problems of Kantscholarship, is to interpret things in themselves as substances withintrinsic properties, and talk of “phenomena” as talk ofthe extrinsic properties of those substances (things in themselves).So in general,

(1): Things inthemselves areF =F is among the intrinsic propertiesof substances
(2): Appearances areF =F is among the extrinsic properties ofsubstances

In particular, this allows Langton to interpret (Existence)and (Humility) as:

(Existence*) Substances with intrinsic properties exist.

(Humility*) We cannot cognize the intrinsic properties ofsubstances.

The apparent tension between these doctrines has vanished. Langton’sinterpretation also allows her to explain why the apparent tensionbetweenHumility and

(Non-spatiality) Things in themselves are not spatial.

is merely apparent because, on her reading (Non-spatiality) isequivalent to:

(Non-spatiality*) Being spatial is not an intrinsic propertyof substances.

This is compatible with (Humility*) because we can know it merely byknowing that being spatial is an extrinsic property in general (thusis not an intrinsic property had by substances), and to know this wedo not need to know anything about the intrinsic properties ofsubstances. Langton thus offers a consistent, elegant interpretationof transcendental idealism that solves several of the oldest andhardest problems in the interpretation of Kant’s philosophy.^[48]

4.5 Problems for Langton’s reading

Much of the critical reaction to Langton (1998) has focused on herreconstruction of Kant’s argument for Humility, but I am not going todiscuss that argument; even if Langton is wrong about how Kant provesHumility, she may still be right about what Humilitymeansand thus what the appearance/thing in itself distinction means (e.g.,Allais 2006).

4.5.1 Textual evidence

There is substantial textual evidence that Kantian appearances haveonly extrinsic properties. For instance, this passage from the“Aesthetic”:

everything in our cognition that belongs to intuition (with theexception, therefore, of the feeling of pleasure and displeasure andthe will, which are not cognitions at all) contains nothing but mererelations, of places in one intuition (extension), alteration ofplaces (motion), and laws in accordance with which this alteration isdetermined (moving forces). (B67)

This, and other passages Langton cites, support attributing to Kantthese theses:

(1): Appearances(phenomena) have only relational properties. (B67, A265/B321,A285/B341)
(2): When we conceiveof an object purely intellectually we conceive of it as havingintrinsic properties. (A274/B330, A277/B333)
(3): In knowingrelational properties we do not know things as they are in themselves.(B67)

However, in none of these passages does Kant directly state thestronger claim that:

(4): Phenomena areextrinsic properties of substances with intrinsicproperties.

It is clear that Kant holds (1)–(3) and less clear that he holds(4). The textual case for (4) is weaker, though not absent. It ispresented below, insub-section 4.5.2.

There is a further textual problem for Langton’s interpretation,though. In at least two passages Kant denies that we can knowrelations between things in themselves:

Space represents no property at all of any things in themselves norany relation of them each other […] (A26/B42)
[…] the things that we intuit are not in themselves what weintuit them to be, nor are their relations so constituted inthemselves as they appear to us. (A42/B59)

In these passages Kant claims that space is not a relation amongthings in themselves, nor are relations among objects “inthemselves” as they appear to us. This is hard to square withLangton’s reading. However, in her (2011) Langton responds to thesetextual objections by suggesting that the relations among things inthemselves of which Kant speaks areinternal relations,relations that supervene on the intrinsic properties of substances.^[49]

4.5.2Phenomena substantiata

One source of resistance to Langton’s interpretation is that Kantargues at length in the “First Analogy of Experience” thatthe categorysubstance can be applied to phenomena:

all appearances contain that which persists (substance) as the objectitself, and that which can change as its mere determination, i.e., away in which the object exists. (A182)

This would appear to contradict Langton’s assertion that things inthemselves are substances, while appearances (phenomena) are merelyproperties of substances.

Langton is well aware that Kant accepts “phenomenalsubstances” and endeavors to explain this within her picture. Indoing so, she compiles a compelling set of textual evidence for heralternative reading of the “First Analogy” and the meaningofsubstance for phenomena. She begins by pointing toAlexander Gottlieb Baumgarten’s notion of aphaenomenasubstantiata, a “substantiated phenomenon”, by whichBaumgarten means a property that we treat as a substance bypredicating other properties of it (Baumgarten,Metaphysica§193 (Ak. 18:150); quoted at Langton 1998: 53). She arguesconvincingly that Kant’s fundamental notion of a substance is of a beingwith properties but which is not a property of anything else.^[50] Only such beings, of which other things are predicated (inhere in)but which are not predicated of (inhere in) anything else, are trulysubstances. However, the properties that are predicated of substancescan also be spoken of as substances, because they themselves haveproperties (which might also have properties, and so on).^[51] These are substantiated phenomena.

The question is, are Kantian empirical substances genuine substancesor mere substantiated phenomena? Do the objects subsumed under theempirical schema of substance (absolute persistence in time) also fallunder the pure category of substance (subjects of inherence whichinhere in nothing further)? If not, then they must be predicated ofsome more fundamental substance, which drives Langton to conclude thatappearances (phenomena) are properties of substances (she does pointout the hesitant terms in which Kant describes phenomena as substances(1998, 57). Langton assembles an impressive array of evidence thatKant does regard empirical “substances” asphaenomenasubstantiata (e.g., A265/B321, A277/B333, Refl. 4421, 4422, 5294,Ak. 28:209). However, in context it is not clear whether Kant has theBaumgarten notion in mind, or whether this Latin expression meanssimply: phenomenal substance. So it is unclear, textually, whetherphenomena are predicated of noumena in theCritique.^[52]

In his metaphysics lectures, and other texts, Kant consistentlydistinguishes the inherence relation (which holds between a propertyand an entity of which it is predicated) from the relation ofground toconsequence:

The world “substance” is clearly ambiguous. One translatesit through the notion of self-sufficiency, i.e., the possibility ofexisting without a ground, but also as the possibility of existingwithout inhering [in something else]. (Ak. 28:1308; Ak. 8:225n,28:562, 28:779, 28:638–9, 28:1041, 28:1104f)

Kant, following Baumgarten, criticizes Spinoza’s definition ofsubstance as “what is in itself and conceived throughitself” (Ethics Id3) because it conflates two notions:(i) a being that is not grounded in, or caused by, anything morefundamental, and (ii) a being that does not inhere in anything morefundamental. The second is the correct definition of substance,according to Kant; by conflating these two notions, Spinoza foreclosesthe following possibility: there are substances distinct from God(they are not modes of God), all of which are grounded in God.

To bring this back to Langton, we need to distinguish two differentclaims:

(i): Phenomena areextrinsic properties of substances (things in themselves). They inherein things in themselves.
(ii): Phenomena exist(at least partly) in virtue of the extrinsic properties of substances(things in themselves). They are grounded in things inthemselves.

Langton attributes (i) to Kant, but her textual case appears tosupport (ii), at best.^[53] This is significant, because (ii) is far less controversial. Forinstance, it is in principle acceptable to the qualifiedphenomenalist, because the extrinsic properties of things inthemselves include (presumably) properties likecausing us to havesuch and such experience.

5. One Object or Two?

Since Karl Ameriks’ classic survey of the literature, Ameriks(1982), it has been customary to divide interpretations oftranscendental idealism into “two object” readings and“one object” readings. By contrast, this article has beenorganized around the distinction between phenomenalist readings, andnon-phenomenalist dual-aspect readings. This section explores therelation between the “one object”/“two object”distinction and the phenomenalist/non-phenomenalist distinction amongdifferent interpretations of Kant’s idealism.

The distinction between “one object” and “twoobject” readings comes down to the question of whetherappearances, in general, are numerically identical to things inthemselves: "one object" readers claim they are (Adickes 1924: 20, 27;Allais 2004: 657; Langton 1998: 13; Westphal 1968: 120), and "twoobject" readers deny this.^[54] Whether all things in themselves are numerically identical toappearances is not at issue, for most one object readers will admitthere could be things that never appear to us (cf. B306, where Kantseems to admit as much) (although it might be misleading to call themthings “in themselves” since they never appear to us, sowe never consider them as they are “in themselves”). Thequalification “in general” is necessary because some“two object” readers will admit that some appearances arealso things in themselves; e.g., many “two object” readerswill admit that, in the case of the self, there is a single object, athing in itself, that appears to itself as a spatiotemporal object (onthis issue, see Adams (1997), Aquila (1979), and Ameriks’discussion of Aquila in his 1982).

However, the characterization of these views as “oneobject” and “two object” is unfortunate, because itis not a commitment of “two object” readings that, foreach appearance, there is one and only one thing in itself thatappears as that object. The “two object” interpreter canhold that each appearance is the appearance of an indefinite pluralityof things in themselves. Nor is the other standard moniker, “oneworld” versus “two world”, helpful, either, for“world” is a technical term in Kant’s metaphysics and hasa very specific meaning.^[55] One can coherently hold a “non-identity” interpretationwhile denying that appearances in space and time constitute a“world” at all.^[56]

This section explores how the identity/non-identity debate relates tothe non-phenomenalist/phenomenalist debate. They have often beenconflated by equating the “two world” interpretation(non-identity) with the phenomenalist one, and conversely, by equatingthe “one world” interpretation (identity) with theanti-phenomenalist one. There are grounds to think, however, thatthese are distinct debates.Section 5.1 I examines whether claims about the numerical identity ornon-identity of appearances and things in themselves are meaningful atall, and, if they are, what warrant we could have for making themwithin Kant’s theoretical philosophy.Section 5 investigates whether, assuming that claims of identity ornon-identityare meaningful, the identity/non-identity debateis orthogonal the phenomenalist/non-phenomenalist debate.Section 5.2 that paradigmatically anti-phenomenalist interpretations (e.g.,Langton 1998) can be understood as non-identity views.Section 5.3 examines some reasons for thinking that the phenomenalistinterpretation is compatible with the “identity” ofappearances and things in themselves.Section 5.4 considers the interpretive landscape in light of these results.^[57]

5.1 Identity between appearances and things in themselves

As Henry Allison and others have pointed out, it is not clear thatthere is any content to the question of whether an appearance isnumerically identical to a thing in itself, outside of moral contexts.^[58] It is relatively clear that in the context of his moral philosophy,Kant wants to assert that one and the same object, a rational agent,can be considered as an appearance and as a thing in itself.Considered as an appearance, a rational agent is subject to conditionsof experience (space, time, and the categories). Considered as a thingin itself, a rational agent can at least consistently be thought of asfree (because independent of the deterministic causal order of spaceand time), while practical reason gives us warrant for positivelyasserting that the agent is free. Kant typically expresses thissolution to the problem of freedom and determinism in terms of thenumerical identity of the appearance of the agent and the agent asthing in itself (e.g., Ak. 5: 105, 114). Practical reason gives bothcontent and warrant to the assertion of numerical identity:content, because the assertion of numerical identity meansthat one and the same noumenal agent is the cause of and thereforeresponsible for the actions of an empirical rational agentover time, andwarrant, because this assumption of the unityof a noumenal agent over time is a presupposition of our ordinarymoral cognition of blame and praise. But neither of these seem to holdin the theoretical use of reason. It is not clear that within thetheoretical use of reason we can give anycontent to theclaim of the numerical identity (or distinctness) of appearances andthings in themselves, nor any warrant for asserting or denying it.^[59]

In defense of the contentfulness of these identity claims, one mightargue that the term “appearance” and “thing initself” each has an extension, a set of objects, and thequestion of identity is perfectly well-formed: do these two sets havea non-empty intersection? If so, at least one appearance is identicalto a thing in itself. But this argument begs the question by assumingthat the question of whether the set of appearances and the set ofthing in themselves has an intersection is itself well-formed; whetherthis is the case is precisely what is at issue.

While many interpreters (notably Adams 1997: 822) think that we canhave no warrant for asserting the identity or non-identity ofappearances and things in themselves in general, and thus think theidentity/non-identity debate (at least in theoretical contexts)concerns something about which Kant must be agnostic, there are thosewho disagree (Stang 2014; cf. Walker 2010). In texts quoted earlier,Kant claims that appearances would cease to exist if there were notminds to experience them. On the assumption that this is not true ofthings in themselves, consider the following argument:

(P1): For anyx, ifx is an appearance,x would not existif there were no minds to experience it.
(P2): For anyx, ifx is a thing in itself,x would existif there were no minds to experience it.
(C): For anyx, ifx is an appearance,x is not a thingin itself.

This argument purports to show that, since appearances and things inthemselves have different modal properties, they must be distinct.Since (P1) and (P2) are claims Kant makes in the context of histheoretical philosophy, this argument provides warrant for denyingidentity on purely theoretical grounds.

5.2 Langton and non-identity

Langton’s view can be interpreted as either an identity reading or anon-identity reading. The difference is somewhat subtle, but it hasimportant consequences. On the identity version of Langton (1998), totalk about things in themselves is to predicate intrinsic propertiesof substances, while to talk about phenomena is to predicate extrinsicproperties ofthose very substances. On the non-identityversion of Langton (1998), phenomena are numerically identical tothose extrinsic properties. This would be a non-identity readingbecause substances are not identical to their properties (eitherextrinsic or intrinsic). By contrast, on the identity reading, anexpression for a phenomenonrefers to a substance. Thedifference between these readings can be illustrated by how they givetruth-conditions for the judgment that some phenomenonx haspropertyF:

(Identity)x hasF =F is amongthe extrinsic properties ofx

(Non-Identity)x hasF =x, anextrinsic property of some substancey (≠x), hasF

While Langton initially explains her view in a way that suggests anidentity reading, she in fact opts for a non-identity reading, forgood reason. Firstly, on the identity reading Kant would have toidentify subjects of predication in empirical judgments withsubstances. This is problematic because it would bring substances intothe world of space and time. For instance, if I can make a judgmentabout this table, then it would be a judgment about the extrinsicproperties of this table, and this table would be a substance withintrinsic properties (although being a table would, presumably, not beone of them). Alternately, if we identify the table as a collection ofextrinsic properties of substances, then we can go on to predicatefurther properties of the table, without having to identify thesubstance or substances of which the table is ultimately predicated.^[60]

5.3 Phenomenalist Dual Aspect Readings

Some scholars have defended what might initially seem like acontradiction in terms: a phenomenalist “one object”(identity) interpretation of appearances and things in themselves.^[61] On such a view, the appearance and the thing in itself are one andthe same object, but considered with respect to different properties:the properties we experience the object as having, and the propertiesit has. On this interpretation, Kant is qualified phenomenalistbecause he holds that:

(Phenomenalism_P) The core physical properties ofobjects in space are grounded in the contents of our experience ofthem.

His attitude to:

(Phenomenalism_E) The existence of objects in spaceis ground partly or wholly in the contents of our experience ofthem.

depends upon how we read it, on this interpretation. On the one hand,we can understand it either as the “de re”claim

(Phenomenalism_E*) (x)(x is anobject in space ⊃ the existence ofx is partly or whollygrounded in our experience ofx)

in which case Kant would reject it, because each such object in spaceis also a thing in itself and, as such, does not depend for itsexistence on our experience of it. On the other hand, we couldunderstand it as thede dicto claim

(Phenomenalism_E**) The fact that there are objectsin space is partly or wholly grounded in our experience of objects inspace.

in which case Kant would accept it, because there being objects inspace depends upon our experiencing objects as in space.

This leads to an important exegetical point. One of the mainmotivations for “non-identity” interpretations arepassages in which Kant claims that appearances would not exist ifthere were not subjects to experience them, e.g., A42/B59. This mightbe thought to directly entail phenomenalism, for, if appearances wouldnot exist without subjects to experience them, but things inthemselves would, thena fortiori appearances and things inthemselves are distinct. This line of reasoning can be representedformally as (P1), (P2) and C from section 5.1. But the identity readercan interpret Kant’s claim “if I were to take away the thinkingsubject, the whole corporeal world would have to disappear” asmeaning: without subjects to experience them, appearances would notexistas appearances, i.e., would not appear. In other words,she can reinterpret (P1) as:

(P1*): For allx,ifx is an appearance, thenx’s existenceas anappearance (=the fact thatx exists and appears) isgrounded in the contents of experience.

But the conjunction of this and (P2) does not entail (C); they arecompatible with the identity reading. These passages do notforce the non-identity interpretation on us. (For more onphenomenalist identity readings see the supplementary article:Phenomenalist Identity Readings and the Problem of Illusion.)

5.4 Assessing the Interpretive Issues

We have seen some reasons to think that the resolutelyanti-phenomenalist reading of Langton (1998) and the phenomenalistreading can be re-interpreted as, respectively, a non-identity readingand an identity reading. One reaction would be to conclude that theinterpretive options are simply more complex than is usuallyappreciated:

	Non-Identity	Identity
	Non-Identity	Epistemic	Metaphysical
Phenomenalist	Aquila (1983), Van Cleve (1999), cf. section 3	N/A	Adickes (1924), Westphal (1968)
Anti-phenomenalist	Alternate version of Langton	Allison (1983/2004), Bird (1962), Prauss (1974)	Langton (1998), Allais (2006)

Table 1

But the distinction between the two different versions of Langton, andbetween the non-identity version of phenomenalism (Aquila 1983; VanCleve 1999) and the identity version of phenomenalism (Adickes 1924;Westphal 1968) is relatively recondite. It depends on thecontroversial assumption that assertions of identity betweenappearances and things in themselves, outside of practical contexts,have a content.

Furthermore, Henry Allison has recently argued that even his view isneutral on the identity/non-identity debate:

although it is sometimes assumed that [the two-aspect reading] commitsKant to a highly implausible one-to-one mapping of the phenomenal andnoumenal, I take that to be a red herring. First, it is one thing todistinguish between things (taken collectively) as they are for us invirtue of the sensible conditions of human cognition and as they mightbe for some putative pure understanding, unburdened by suchconditions, and quite another to affirm a one-to-one correspondence orisomorphism between the members of the two domains. (Allison 2004: 459note 19; cf. Allison 1987: 168)

Allison’s idea is that the distinction between the empirical and thetranscendental standpoint is a distinction between how they considerobjectsas a whole, not how they consider particular objects.The Epistemic reading is not committed to Identity, but neither is itcommitted to Non-Identity. So an Identity version of the Epistemicreading is possible (according to which we can consider each objectindividually from either standpoint), as is an Epistemic reading thatis neither an Identity nor a Non-Identity reading (on which we remainagnostic as to whether objects considered from one standpoint arenumerically identical to objects considered from another).^[62] So we might conclude that our interpretive options are even morenumerous than we initially thought:

	Neither Identity nor Non-Identity	Non-Identity	Identity
	Neither Identity nor Non-Identity	Non-Identity	Epistemic	Metaphysical
Phenomenalist	N/A	Aquila (1983), Van Cleve (1999), cf. section 3	N/A	Adickes (1924), Westphal (1968)
Anti-phenomenalist	Allison (1983/2004)	Alternate version of Langton	Bird (1962), Prauss (1974), alternate version of Allison(1983/2004),	Langton (1998), Allais (2006)

Table 2

But notice we now have doubling of interpretations: identity andnon-identity versions of Langton (1998), identity and non-identityversions of phenomenalist views, and identity and “neitheridentity nor non-identity” versions of Allison.

However, if one thinks that claims of identity between appearances andthings in themselves are contentless (see section 5.1), at leastoutside of the context of practical philosophy, then the menu ofinterpretive options will appear as:

Phenomenalist	Anti-Phenomenalist
Phenomenalist	Epistemic	Metaphysical
Aquila (1983), Van Cleve (1999), Adickes (1924), Westphal(1968), cf. section 3	Allison (1983/2004), Bird (1962), Prauss (1974)	Langton (1998), Allais (2006)

Table 3

On such a reading, there is no substance, outside of the practicalcontext, to the question of whether an appearance isnumericallyidentical to a thing in itself, so the identity and non-identityversions of, e.g., phenomenalism, are equivalent.^[63] If one holds instead that these identity claims have a content butthat we cannot know them on theoretical grounds alone (see section5.1) then one will likewise see these interpretive options as soconstrained, because, although there is a difference in contentbetween, say, the identity and non-identity versions of phenomenalism,Kant must be agnostic as to which is true.

6. Things in themselves,noumena, and the transcendental object

Up to this point, we have focused primarily on the nature of Kantianappearances, and their relation to things in themselves, questions (a)and (c) from section one. However, one of the main questions that mustbe answered in any interpretation of Kant’s transcendental idealismis, what are things in themselves? Obviously, differentinterpretations will give very different answers to this question:

Phenomenalist interpretations. Perhaps the best statement ofthe phenomenalist interpretation of things in themselves is given byErich Adickes (1924: 14–19): things in themselves are aplurality of mind-independent centers of force. On this view, thingsin themselves are just what we pre-theoretically took ordinaryspatiotemporal objects to be: objects that exist, and possess theircore physical properties, wholly independently of our representationsof them, and which are (among) the causal inputs to our perceptualfaculties (a variant of this thought is expressed by Ameriks 2003:23–25).

Epistemic interpretations: On the epistemic reading, thingsin themselves are simply objects considered independently of ourdistinctively spatiotemporal form of intuition. Thus, they are objectsconsidered as objects of a discursive cognition in general. This veryabstract thought is not the basis of any cognition, however; it ismerely a reminder that space and time are epistemic conditions,without which we cannot cognize any object.

Metaphysical “dual aspect” interpretations. Onthis family of interpretations, things in themselves are objects witha given set of properties. Different interpretations give a differentanswer as to which set of properties constitute things “as theyare in themselves”. On Langton’s reading, for instance, thingsin themselves are substances with intrinsic properties.

In this section I want to distinguish “things inthemselves” from other, closely related Kantian notions:noumena, and the “transcendental object”.

6.1Phenomena andnoumena

In the section “On the ground of the distinction of all objectsintophenomena andnoumena”, which hesubstantially revised for the B Edition, Kant reiterates his argumentthat we cannot cognize objects beyond the bounds of possibleexperience, and introduces a complex distinction between phenomena andnoumena.

Fortunately, it is relatively clear what phenomena are:“appearances to the extent that as objects they are thought inaccordance with the unity of the categories are calledphenomena” (A249). Earlier, in the “Aesthetic”, Kanthad defined appearance as: “the undetermined object of anempirical intuition” (A20/B34). All objects of empiricalintuition are appearances, but only those that are “thought inaccordance with the unity of the categories” are phenomena. Forinstance, if I have a visual after-image or highly disunified visualhallucination, that perception may not represent its object asstanding in cause-effect relations, or being an alteration in anabsolutely permanent substance. These would be appearances but notphenomena. The objects of “universal experience”, asdefined in section 3, are phenomena because the categories determinethea priori conceptual form; universal experience representsits objects under the unity of the categories.

Kant’s then introduces the concept of noumena:

if, however, I suppose that there be things that are merely objects ofthe understanding and that, nevertheless, can be given to anintuition, although not to sensible intuition (ascoram intuitiintellectuali), then such things would be called noumena(intelligibilia). (A249)

The concept of a noumenon, as defined here, is the concept of anobject of cognition for an intellect that is not, like ours,discursive, and thus has a non-sensible form of intuition, which Kanthere designates “intellectual intuition”.^[64] A sensible intuition is one that can only intuit objects by beingcausally affected by them; a non-sensible intuition is one in whichthe intuition of the object brings the object into existence. Thus,the concept of a noumenon is the concept of an object that would becognized by an intellect whose intuition brings its very objects intoexistence. Clearly, we do not cognize any noumena, since to cognize anobject for us requires intuition and our intuition is sensible, notintellectual.

Kant then connects the concept of noumena to things in themselves:

it also follows naturally from the concept of an appearance in generalthat something must correspond to it which is not in itselfappearance, for appearance can be nothing for itself and outside ofour kind of representation; thus, if there is not to be a constantcircle, the word "appearance" must already indicate a relation tosomething the immediate representation of which is, to be sure,sensible, but which in itself, without this constitution of oursensibility (on which the form of our intuition is grounded), must besomething, i.e., an object independent of sensibility. Now from thisarises the concept of anoumenon, which, however, is not atall positive and does not signify a determinate cognition of somethingin general, in which I abstract from all form of sensible intuition.(A251–2)

This passage begins with the familiar point that the very concept ofappearance requires that there be something that is not appearancethat appears. Usually Kant makes this point using the concept“things in themselves” (e.g., in theProlegomena(Ak. 4:314–5); cf. Bxxvi–xxvii, B306, and B307). However,here he claims that this idea—that it cannot be“appearances all the way down”—brings with it theidea of noumena. This is puzzling. Why must whatever it is that appearto us as phenomena be conceived of as an objects of intellectualintuition?

Kant clarifies precisely this point in the B Edition by distinguishingbetween a positive and a negative sense of “noumena”:

If by a noumenon we understand a thinginsofar as it is not anobject of our sensible intuition, because we abstract fromthe manner of our intuition of then this is a noumenon in thenegative sense. But if we understand by that anobject of a non-sensible intuition then we assume aspecial kind of intuition, namely intellectual intuition, which,however, is not our own, and the possibility of which we cannotunderstand, and this would be the noumenon in apositive sense. (B307)

Noumena in a positive sense are simply noumena as Kant originallydefined that notion in the A edition: objects of an intellectual(non-sensible) intuition. The negative concept of noumena, however, issimply the concept of objects that are not spatiotemporal (not objectsof our sensible intuition, namely space and time). But then it followsthat things in themselves are noumena in the negative sense,retrospectively clarifying the passage from the A edition quotedimmediately above, where Kant seems to draw from the“Transcendental Aesthetic” the conclusion that there arenoumena: the concept of appearance requires that something appears,and this must be a negative noumena.

Putting these pieces together we can see that “things inthemselves” [Dinge an sich selbst] and (negative)“noumena” are concepts that belong to two differentdistinctions: “thing in itself” is one half of theappearance/thing in itself distinction, which Kant originally definedat A491/B519 in terms of their existence: appearances have noexistence “grounded in themselves” while things inthemselves do. “Noumena” is one half of the distinctionphenomena/noumena which Kant characterizes at B307 as the distinctionbetween what can be an object of our sensible spatiotemporal intuitionand what cannot be an object of sensible intuition. (Kant here appearsto overlook the possibility of objects of sensible butnon-spatiotemporal intuition). One is a distinction in what ground theexistence of objects; the other is a distinction in what kinds ofintuition can present those objects. However, we can make a connectionbetween them: things in themselves, the objects whose existence is“ground in itself”, and which appear to us in space andtime, cannot be objects of any sensible intuition, so they arenegative noumena. Whether, additionally, they are also objects of anintuitive intellect, is a separate matter. This is a point about therelations among these concepts; it holds whether or not they arepossibly instantiated.

6.2 The transcendental object =X

In the “Phenomena and noumena” section, Kant distinguishesthe concept of a noumenon from the concept of a “transcendentalobject” (A250). This is a reference to a notion introduced inthe A version of the “Transcendental Deduction”:

The pure concept of the transcendental object (which in all of ourcognition is really one and the same =X) is that which in allof our empirical concepts in general can provide relation to anobject, i.e., objective reality. Now this concept cannot contains anydeterminate intuition at all, and therefore contains nothing but thatunity which must be encountered in a manifold of cognition insofar asit stands in relation to an object. (A109; cf. A104)

The “concept of a transcendental object” might befruitfully thought of as “the transcendental concept of anobject”: the concept of “object” that makesexperience possible. Our mind’s synthesis of representations intoexperience of objects is guided and made possible by the idea thatthere is a way objects are that must be tracked by our representationsof them. This wholly abstract concept of “a way thingsare” is the concept of the transcendental object =X, theindeterminate concept of the “target” of ourrepresentational activity. Consequently, the concept of thetranscendental object must be distinct from the concept of“things in themselves” or “negative noumena”.The concept of things in themselves is the concept of the (unknowableby us) objects (or aspects of objects) that appear to us the 3D worldof space and time. They are the grounds of phenomena, while thetranscendental object is the very abstract idea of those objects inspace and time as the targets of our cognitive activity.

Another way to appreciate this distinction is to consider thedifference in why these notions of object (noumena, transcendentalobject) are unknowable by us. We cannot cognize things in themselvesbecause cognition requires intuition, and our intuition only everpresents appearances, not things in themselves. We cannot cognize thetranscendental object because the transcendental object is a purelyschematic, general idea of empirical objectivity. Whenever we cognizea determinate empirical object we are cognitively deploying thetranscendental concept of an object in general, but we are not comingto know anything about the object of that concept as such.

This is Kant’s point in “phenomena and noumena” when hewrites:

This transcendental object cannot even be separated from the sensibledata, for then nothing would remain through which it would bethought. It is therefore no object of cognition in itself, but onlythe representation of appearances under the concept of an object ingeneral, which is determinable through the manifold of thoseappearances. (A250–1)

The (negative) concept of a noumenon is the concept of an object thatis not an object of our sensible spatiotemporal intuition. But thetranscendental object makes no sense in abstraction from intuition,because it is merely the abstract concept that the unity of ourintuitions must have in order to constitute experience of an object(cf. Allison’s classic 1968 paper).

7. Conclusion

This article has traced the meaning of transcendental idealism,sometimes referred to as “critical” or“formal” idealism, through the text of theCritique ofPure Reason and various interpretive controversies. Historically,the main question dividing different interpretations is whether Kantis a phenomenalist about object in space and time and, if so, in whatsense. The phenomenalist interpretation of Kant, dominant among Kant’simmediate predecessors and later German idealists, was challenged intwentieth century Anglophone scholarship by, among others, GrahamBird, Gerold Prauss, and Henry Allison. Some later scholars haveretained a central idea of these scholars’ reading—thatthe appearance/thing in itself distinction is a distinction betweendistinct aspects of objects, not distinct kinds of objects—whilejettisoning the purely epistemological interpretation of Kant’sidealism. The meaning and philosophical significance of“transcendental idealism” has been debated by Kant’sreaders since 1781, and this debate shows no sign of abating any timesoon.

Bibliography

Works of Kant

The standard German edition of Kant’s works is:

[Ak.] Königlichen Preußischen (later Deutschen)Akademie der Wissenschaften (ed.), 1900–,Kants gesammelteSchriften, Berlin: Georg Reimer (later Walter De Gruyter).

The most authoritative English translations of Kant’s works arein:

Guyer, P. and A. Wood (eds.), 1992–,The CambridgeEdition of the Works of Immanuel Kant, Cambridge: CambridgeUniversity Press.

Individual volumes used in the preparation of this entry are:

Allison, H. and P. Heath (eds.), 2002,Theoretical Philosophyafter 1781, Cambridge: Cambridge University Press.
Guyer, P. and A. Wood (eds.), 1998,Critique of PureReason, Cambridge: Cambridge University Press.
Zweig, A. (ed.), 1999,Correspondence, Cambridge:Cambridge University Press.

We refer to certain Kantian works by the following abbreviations:

[Prolegomena]Prolegomena to any futuremetaphysics. Translation by Gary Hatfield inTheoreticalPhilosophy after 1781.
[On a discovery]On a discovery according to whichall future critiques of reason have been rendered superfluous by aprevious one. Translation by Henry Allison inTheoreticalPhilosophy after 1781.

Other Primary Sources

Fichte, J.G., 1845–1846,Johann Gottlieb Fichtessämtliche Werke, edited by I. H. Fichte, 8 vols, Berlin:Veit.
Jacobi, F.H., 1812,Werke, edited by F. Roth and F.Köppen, 6 vols, Leipzig: Fleischer.

Secondary Sources

Abela, P., 2002,Kant’s Empirical Realism, Oxford: OxfordUniversity Press.
Adams, R., 1997, “Things in Themselves”,Philosophy and Phenomenological Research, 57:801–825.
Adickes, E., 1924,Kant und das Ding an Sich, Berlin: PanVerlag.
–––, 1929,Kants Lehre von der doppeltenAffektion unseres Ichs als Schlüssel zu seinerErkenntnistheorie, Verlag von J.C.B. Mohr: Tübingen.
Allais, L., 2003, “Kant’s transcendental idealism andcontemporary anti-realism”,International Journal ofPhilosophical Studies, 11: 369–392.
–––, 2004, “Kant’s “OneWorld”: Interpreting Transcendental Idealism”,BritishJournal for the History of Philosophy, 12: 655–684.
–––, 2006, “Kant on Intrinsic Natures: aCritique of Langton”,Philosophy and PhenomenologicalResearch, 73: 143–169.
–––, 2007, “Kant’s Idealism and theSecondary Quality Analogy”,Journal of the History ofPhilosophy, 45: 459–484.
–––, 2015,Manifest Reality: Kant’s Idealismand his Realism, Oxford: Oxford University Press.
Allison, H., 1968, “Kant’s Concept of the TranscendentalObject”,Kant-Studien, 59: 165–186.
–––, 1973, “Kant’s Critique ofBerkeley”,Journal of the History of Philosophy, 11:43–63.
–––, 1976, “The Non-spatiality of Thingsin Themselves for Kant”,Journal of the History ofPhilosophy, 14: 313–321.
–––, 1983,Kant’s TranscendentalIdealism, New Haven: Yale University Press.
–––, 1987, “Transcendental Idealism: TheTwo Aspect View”, in Ouden and Moen (eds.),New Essays onKant, 155–178.
–––, 2004,Kant’s TranscendentalIdealism, New Haven: Yale University Press. Revised and EnlargedEdition.
Ameriks, K., 1982, “Recent Work on Kant’s TheoreticalPhilosophy”,The Philosophical Quarterly, 19:1–24.
–––, 1992, “Kantian Idealism Today”,History of Philosophy Quarterly, 9: 329–342.
–––, 2003,Interpreting Kant’s ThreeCritiques, Oxford: Oxford University Press.
Aquila, R., 1979, “Things in Themselves: Intentionality andReality in Kant”,Archiv Fur Geschichte derPhilosophie, 61: 293–307.
–––, 1983,Representational Mind: A Study ofKant’s Theory of Knowledge, Bloomington: Indiana UniversityPress.
Beck, L.W., 1960,A Commentary on Kant’s Critique of PracticalReason, Chicago: University of Chicago Press.
Beiser, F., 1987,The Fate of Reason: German Philosophybetween Kant and Fichte, Cambridge, MA: Harvard UniversityPress.
–––, 2002,German Idealism: The Struggleagainst Subjectivism, 1781–1801, Cambridge, MA: HarvardUniversity Press.
Bennett, J., 1966,Kant’s Analytic, Cambridge: CambridgeUniversity Press.
Bird, G., 1962,Kant’s Theory of Knowledge, London:Routledge & Kegan Paul.
–––, 2000, “Review ofKantianHumility”,The Philosophical Quarterly, 50:105–108.
Chignell, A., 2010, “Causal Refutations of Idealism”,The Philosophical Quarterly, 60: 487–507.
Cohen, H., 1871/1885,Kants Theorie der Erfahrung,Berlin: Dümmler. Third revised edition, 1885. Reprinted in Cohen,Werke, H. Holzhey and H. Weidebach (eds.), Hildesheim: G.Olms.
–––, 1907,Kommentar zu Immanuel KantsKritik der reinen Vernunft, Leipizig: Meiner.
Collins, A., 1999,Possible Experience, Berkeley and LosAngeles: University of California Press.
Cummins, P., 1968, “Kant on Outer and InnerIntuition”,Noûs, 2: 271–292.
Dicker, G., 2008, “Kant’s Refutation of Idealism”,Noûs, 42: 80–108.
–––, 2011, “Kant’s Refutation of Idealism:a Reply to Chignell”,The Philosophical Quarterly, 61:175–183.
Dunlop, K., 2009, “The Unity of Time’s Measure: Kant’s Replyto Locke”,Philosophers’ Imprint, 9:1–31.
Drexler, H., 1904,Die doppelte Affektion des erkennendenSubjekts, Beuthen o.S.: Th. Kirch.
Dryer, D.P., 1966,Kant’s Solution for Verification inMetaphysics, London: Allen & Unwin.
Emundts, D., 2008, “Kant’s Critique of Berkeley’s Concept ofObjectivity”, in D. Garber and B. Longuenesse (eds.),Kantand the Early Moderns, Princeton: Princeton UniversityPress.
–––, 2010, “The Refutation of Idealism andthe Distinction betweenPhenomena andNoumena”, in P. Guyer (ed.),The CambridgeCompanion to Kant’s Critique of Pure Reason, Cambridge: CambridgeUniversity Press.
Erdmann, B., 1878,Kants Kriticismus in der ersten und in derzweiten Auflage der Kritik der reinen Vernunft, Leipzig:Voss.
Falkenstein, L., 1991, “Kant, Mendelssohn, Lambert, and theSubjectivity of Time”,Journal of the History ofPhilosophy, 29: 227–251.
–––, 2000, “Langton on Things inThemselves”,Kantian Review, 5: 49–64.
Findlay, J.N., 1981,Kant and the Transcendental Object,Oxford: Clarendon Press.
Förster, E., 2012,The Twenty Five Years of Philosophy: ASystematic Reconstruction, trans. B. Bowman, Cambridge, MA:Harvard University Press.
Gram, M., 1975, “The Myth of Double Affection”, inWerkmeister (ed.),Reflections on Kant’s Philosophy.University of Florida Press: Gainesville.
–––, 1981, “Intellectual Intuition: TheContinuity Thesis”,Journal of the History of Ideas,42:287–304.
Grier, M., 2001,Kant’s Doctrine of TranscendentalIllusion, Cambridge: Cambridge University Press.
Guyer, P., 1983, “Kant’s Intentions in the Refutation ofIdealism”,The Philosophical Review, 92:329–383.
–––, 1987,Kant and the Claims ofKnowledge, Cambridge: Cambridge University Press.
Heidegger, M. 1929.Kant und das Problem der Metaphysik.Vittorio Klostermann: Frankfurt a/M.
Hanna, R., 2000, “The Inner and the Outer: Kant’s‘Refutation’ Reconsidered”,Ratio, 13:146–174.
Hogan, D., 2009a, “How to Know Unknowable Things inThemselves ”,Noûs, 43: 49–63.
–––, 2009b, “Noumenal Affection”,The Philosophical Review, 4: 501–532.
Kemp Smith, N., 1962,A Commentary on Kant’s Critique of PureReason, New York: Humanities Press.
Köhnke, K., 1986,Entstehung und Aufstieg desNeukantianismus:die deutsche Universitatsphilosophiezwischen Idealismus und Positivismus, Frankfurt am Main:Suhrkamp.
Langton, R., 1998,Kantian Humility, Oxford: OxfordUniversity Press.
–––, 2011, “Kant’s Phenomena: Extrinsic orRelational Properties? A Reply to Allais”,Philosophy andPhenomenological Research, 73: 170–185.
Marshall, C., 2013, “Kant’s Appearances and Things inThemselves as Qua-Objects”,The PhilosophicalQuarterly, 63: 520–545.
Matthews, H.E., 1969, “Strawson on TranscendentalIdealism”,The Philosophical Review, 19:204–220.
McDaniel, K., Ms, “Kantian Ignorance”.
Paton, H.J., 1936,Kant’s Metaphysic of Experience, 2vols., London: Allen & Unwin.
Patton, L., 2005, “The Critical Philosophy Renewed: TheBridge Between Hermann Cohen’s Early Work on Kant and Later Philosophyof Science”,Angelaki, 10: 109–118.
Prauss, G., 1974,Kant und das Problem der Dinge an Sich,Bonn: Grundman.
Richardson, A., 2003, “Conceiving, Experiencing, andConceiving Experience: Neo-Kantianism and the History of the Conceptof Experience”,Topoi, 22: 55–67.
Robinson, H., 1994, “Two Perspectives on Kant’s Appearancesand Things-in-Themselves”,Journal of the History ofPhilosophy, 33: 411–441.
Rosefeldt, T., 2001, “Review ofKantianHumility”,Zeitschrift für philosophischeForschung, 9 (2001): 236–69.
–––, 2007, “Dinge an sich undsekundäre Qualitäten”, in J. Stolzenberg (ed.),Kant in der Gegenwart, Berlin, New York: Walter de Gruyter,167–209.
–––, 2013, “Subject-Dependence andTrendelenburg’s Gap”, inAkten des XI. InternationalenKant-Kongresses, New York and Berlin: Walter de Gruyter, vol. 2,755–64.
Sassen, B., 2000,Kant’s Early Critics, Cambridge:Cambridge University Press.
Schopenhauer, A., 1938,Sämtliche Werke, edited byArthur Hubscher, Leipzig: Brockhaus.
Sellars, W., 1968,Science and Metaphysics: Variations onKantian Themes, London: Routledge.
Stang, N., 2012, “Kant on Complete Determination andInfinite Judgment”,British Journal for the History ofPhilosophy, 20: 1117–1139.
–––, 2013, “Freedom, Knowledge andAffection”,Kantian Review, 18(1): 96–106.
–––, 2014, “The Non-Identity ofAppearances and Things in Themselves”,Noûs,48(1): 106–136.
–––, 2015, “Who’s Afraid of DoubleAffection?”Philosophers’ Imprint, 15:1–28.
Strawson, P.F., 1966,The Bounds of Sense, London:Methuen.
Turbayne, C., 1955, “Kant’s Refutation of DogmaticIdealism”,Philosophical Quarterly, 5:225–244.
–––, 1969, “Kant’s Relation toBerkeley”, in L.W. Beck (ed.),Kant Studies Today, LaSalle, IL: Open Court.
Vaihinger, H., 1881/1892,Commentar zur Kants Kritik derreinen Vernunft, 2 vols., Stuttgart: W. Spemann.
–––, 1884, “Zu KantsWiderlegung desIdealismus”,Strassberger Abhandlungen zur Philosophie,Freiburg: Mohr.
Van Cleve, J., 1999,Problems from Kant, Oxford: OxfordUniversity Press.
Vogel, J., 1993, “The Problem of Self-Knowledge in Kant’s‘Refutation of Idealism’”,Philosophy andPhenomenological Research, 53: 875–887.
Walker, R., 1985, “Idealism: Kant and Berkeley”, in J.Foster and H. Robinson (ed.),Essays on Berkeley, Oxford:Oxford University Press.
–––, 2010, “Kant on the Number ofWorlds”,British Journal for the History of Philosophy,18: 821–843.
Weldon, T.D., 1958,Kant’s Critique of Pure Reason,Oxford: Clarendon Press.
Westphal, M., 1968, “In Defense of the Thing inItself”,Kant-Studien, 59: 118–141.
Westphal, K.R., 2000, “Kant, Hegel, and the fate of‘the’ Intuitive Intellect”, in S. Sedgewick (ed.),The Reception of Kant’s Critical Philosophy, CambridgeUniversity Press.
Wilson, M., 1971, “Kant and the ‘Dogmatic Idealism ofBerkeley”,Journal of the History of Philosophy, 9:459–475. Reprinted in Wilson (ed.), 1999,Ideas andMechanism: Essays on Early Modern Philosophy, Princeton:Princeton University Press: 277–293.

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