Perceptual experiences are often divided into the following threebroad categories: veridical perceptions, illusions, andhallucinations. For example, when one has a visual experience as of ared object, it may be that one is really seeing an object and its redcolour (veridical perception), that one is seeing a green object(illusion), or that one is not seeing an object at all(hallucination). Many maintain that the same account should be givenof the nature of the conscious experience that occurs in each of thesethree cases. Those who hold a disjunctive theory of perception denythis. Disjunctivists typically reject the claim that the same kind ofexperience is common to all three cases because they hold views aboutthe nature of veridical perception that are inconsistent with it.

Disjunctivists are often naïve realists, who hold that when oneperceives the world, the mind-independent objects of perception, suchas tables and trees, are constituents of one’s experience. In othercases, such as hallucinations, it seems out of the question that suchobjects are constituents of one’s experience. It follows that on anaïve realist view, the veridical perceptions and hallucinationsin question have a different nature: the former have mind-independentobjects as constituents, and the latter do not.

• 1. Introduction
• 2. Varieties of Disjunctivism
  • 2.1 Ways of Formulating Disjunctivism
  • 2.2 Disjunctivism about Intentional Content
  • 2.3 Disjunctivism about Phenomenal Character
  • 2.4 Epistemological Disjunctivism
• 3. Arguments for Disjunctivism
  • 3.1 An Argument for Disjunctivism as the Default View
  • 3.2 An Epistemological Argument
  • 3.3 A Phenomenological Argument
  • 3.4 An Argument from Epistemic Modesty
  • 3.5 An Argument from Demonstrative Reference
  • 3.6 Further Motivations for Disjunctivism
• 4. Objections to Disjunctivism
  • 4.1 The Explanatory Power of the Common Kind Claim
  • 4.2 The Causal Argument Against Disjunctivism
  • 4.3 Neither Conjunctivism Nor Disjunctivism
• 5. Disjunctivist Accounts of Hallucination and Illusion
  • 5.1 Hallucination
  • 5.2 Illusion
• 6. Disjunctivism and the Causal Theory of Perception
• 7. Conclusion
• Bibliography
• Academic Tools
• Other Internet Resources
• Related Entries

1. Introduction

Disjunctivists and their opponents agree that veridical perceptions,illusions and hallucinations have something in common, in so far asthey agree that such mental events should be grouped together as beingperceptual experiences. They also agree that there are differences tobe marked between them, hence the different labels for them. However,they disagree when it comes to specifying what these commonalities anddifferences consist in. What distinguishes the disjunctivist theory isits rejection of a ‘common kind claim’—the claimthat the conscious perceptual experiences that are involved in casesof veridical perception, illusion and hallucination have the samenature. If one accepts that the same kind of conscious experienceoccurs in all three cases, then this imposes a constraint on theaccount one can give of the kind of conscious event that occurs when oneveridically perceives the world. Disjunctivists deny that ouraccounts of veridical perception should be constrained in this way. Sothe disjunctivist view of perceptual experience can be regarded as anegative thesis—the rejection of a common kind claim—thatis adopted in defence of a positive view of veridical perception.

Those who hold a disjunctive theory of perception do not deny thatit is possible to have a hallucination of anF that is subjectivelyindistinguishible from a veridical perception of anF. That is, they donot deny that it is possible for one to have a hallucination such thatone cannot tell through introspection alone that it is not a veridicalperception of anF. So associated with the disjunctivist’smetaphysical stance, namely the rejection of the common kind claim, isan epistemological proposal that emphasises limitations on asubject’s capacity to tell what kind of experience she isundergoing on the basis of introspection alone. For example, J.M.Hinton, an early proponent of the disjunctive theory,acknowledges that both a hallucination of anF and a veridicalperception of anF can appear, from the inside, to be a veridicalperception of anF. However, he holds that it is a mistake to assumethat this appearance is to be explained by the thesis that theseexperiences share a common nature that is manifest to one when has theexperiences.

Hinton is generally credited with being the first to demarcate clearlythe disjunctivist stance, and the fact that the disjunctive theory ofperception is so named is due to his way of framing the view. Hinton(1967 and 1973) argued that we should understand a statement about howthings sensorily appear to a subject to be equivalent to a disjunctivestatement thateither one is veridically perceiving such andsuchor one is suffering an illusion (or hallucination); andsuch statements are not to be regarded as making a report about adistinctive mental event or state that is common to these disjointsituations. (For discussion of the historical significance of Hinton,see Snowdon 2008). The disjunctive approach to perceptual experiencewas later developed by Paul Snowdon (1980–81), John McDowell(1982), and M.G.F. Martin (2002), among others.

2. Varieties of Disjunctivism

There are some significant differences between some of the views thatfall under the disjunctivist label. Disjunctivists are united in theirrejection of a common kind claim, and they generally adopt this stancebecause they hold views about the nature of veridical perception thatthey take to be inconsistent with it. However, not all disjunctivistsare in agreement over the account that should be given of veridicalperception, and not all disjunctivists are in agreement over thequestion of the accounts that should be given of hallucinations andillusions. The different disjunctivist proposals about illusion andhallucination are discussed in section 5. This section focuses on someof the main differences between the accounts that disjunctivists offerof the relevant features that they claim veridical perceptions have,and which they claim hallucinations lack.

The fact that there are some significant differences between some ofthe views that fall under the disjunctivist label can introducecomplications when it comes to trying to formulate more precisely adistinctivelydisjunctivist commitment that is common to allof them. So first (in section 2.1) some further remarks are in orderconcerning some of the different ways in which disjunctivism ingeneral has been formulated in the literature. When it comes toassessing arguments that are presented as being either for or againstdisjunctivism it is obviously going to be important to be sensitive tothe question of which formulation of disjunctivism is in play. Giventhat many who adopt a disjunctivist position do so in defence of aparticular account of veridical perception, it will also be importantto assess which disjunctivist commitment, if any, is actually entailedby their view of the nature of veridical perception.

2.1 Ways of Formulating Disjunctivism

2.1.1 Fundamental Kind Disjunctivism

Disjunctivists maintain that veridical perceptions and hallucinationsare mental events (or states) of different kinds. However, we needfurther clarification of what this claim amounts to, for there is anunderstanding of this claim that it may be open to a non-disjunctivistto accept as well. For example, the non-disjunctivist can accept thatthe terms ‘veridical perception’ and‘hallucination’ mark useful distinctions betweenperceptual experiences that may, in certain contexts, be ofexplanatory significance. So the non-disjunctivist may agree thatthere is a sense in which veridical perceptions and hallucinations canbe thought of as perceptual experiences of different kinds. Forsimilar reasons the disjunctivist can agree that there is a sense inwhich veridical perceptions and hallucinations can be thought of asexperiences of the same kind. For disjunctivists do not in generaldeny that veridical perceptions and hallucinations canhaveanything in common.

One formulation of disjunctivism invokes the notion of afundamental kind. (This formulation is principally due toMartin, but see also Snowdon 2005a, p. 136. For discussion of thisformulation, see Logue 2013). According to this formulation, thedisjunctivist is committed to denying that veridical perceptions,illusions and hallucinations are conscious events of the samefundamental kind. The assumption here is that for mentalevents, there is a most specific answer to the question, ‘What isit?’ that tells us whatessentially the mental event is,and thereby specifies itsfundamental kind. On thisformulation, the disjunctivist is committed to denying that whateverfundamental kind of conscious event occurs when one is veridicallyperceiving the world, that kind of event can occur whether or not oneis veridically perceiving. Let us call a view of this sortfundamental kind disjunctivism.

While those who advocate this form of disjunctivism reject a commonkind claim, namely the claim that veridical perceptions andhallucinations are mental events of the samefundamental kind,they may allow that veridical perceptions and hallucinations havesomething in common. So they may allow that there is a kindK thatveridical perceptions and hallucinations can both instantiate. However, whatthey deny is that such a kindK is thefundamental kind ofconscious event occurring when a subject veridically perceives theworld.

Not all accept the metaphysical assumption that mental events (orstates) have a ‘fundamental’ kind. A disjunctive theory ofperception is often adopted in defence of a particular account ofveridical perception, such as naïve realism, and Byrne and Logue(2008) question whether any controversial claim about fundamental kindsis needed in order to defend a naïve realist view of veridicalperception. They suggest that one may hold a naïve realist viewaccording to which mind-independent objects, such as tables and trees,are constituents of the experience one has when one veridicallyperceives the world, without being committed to a further claim aboutwhat theessence of such episodes consists in. They also notethat naïve realism is often motivated by phenomenologicalconsiderations, and they question whether introspective reflection onthe phenomenology of the experience one has when one veridicallyperceives the world puts one in a position to learn anything about theessence of the experience one is having.

2.1.2 The ‘Distinct Mental Feature’ Formulation

Those who reject the metaphysical assumption that mental events (orstates) have a ‘fundamental’ kind may instead formulatetheir disjunctivist stance in terms of the claim that the differencesbetween the kind of mental event that occurs when one veridicallyperceives the world and the kind of mental event that occurs when onehallucinates are due to differences inmental features ofthe events in question. The thought here is that the fact that thereis a respect in which two mental events (or states) are different maynot be due to the fact that they differ in some mental respect, andwhile we might type mental events and states in a variety of differentways, for a variety of different purposes, we can distinguish a way ofclassifying such events and states that focuses solely on their mentalfeatures. For example, although there may be a context in which itsuits our purposes to group together the beliefs of a subject that aretrue, it is not generally thought that a belief’s being true is amental feature of that state.

According to this alternative way of formulating disjunctivism, thedisjunctivist holds that veridical perceptions and hallucinationsdiffer mentally in some significant respect—i.e., there arecertain mental features that veridical perceptions have thathallucinations cannot have. So the disjunctivist rejects the claimthat the differences between a case of veridical perception and a caseof hallucination can simply be due to differences in the extra-mentalstates of affairs that obtain in those situations. Note, however, thatthis formulation of the disjunctivist commitment leaves open thepossibility that veridical perceptions and hallucinations can have atleastsome mental features in common. (See Logue 2012a, 2013,and 2014.) There is a sense, then, in which it thereby leaves open thepossibility that there can be a common mental element to veridicalperception and hallucination.

2.1.3 The ‘No-Common-Mental-Element’ Formulation

Byrne and Logue (2008) propose that the label ‘metaphysicaldisjunctivism’ be reserved for an account of perceptualexperience that commits to the claim there isno common mental element to veridical perception andhallucination. According to Byrne and Logue, those who deny that veridicalperceptions and hallucinations are mental events of the samefundamental kind (see section 2.1) are nottherebycommitted to ‘metaphysical disjunctivism’, asByrne and Logue use this label. For as they point out, those who rejectthe claim that veridical perceptions and hallucinations are mentalevents of the same fundamental kind need not deny that there is acommon mental element to veridical perception and hallucination. So itis worth bearing in mind the particular use to which Byrne and Logueput the label ‘metaphysical disjunctivism’, as others wouldnaturally characterise fundamental kind disjunctivism as a metaphysicaldisjunctivist thesis.

As we’ve seen, the issue of how precisely to formulate adistinctivelydisjunctivist commitment is notuncontroversial. For now we can at least say that the minimalcommitment of a view that can be labelled a disjunctivist theory ofperception is that veridical perceptions and hallucinations differmentally in some significant respect—i.e., there are certainmental features that veridical perceptions have that hallucinationscannot have. So we can mark some of the differences between views thatfall under the disjunctivist label by invoking the notion of‘disjunctivism aboutX’, whereX is therelevant mental feature that it is claimed differs in cases ofveridical perception and hallucination. This procedure is adopted inthe following two sections. If the disjunctivist aboutXmakes the additional claim that the particular mentalfeature,X, that is unique to the case of veridicalperception is essential to the fundamental kind of mental event it is,then they will also be a fundamental kind disjunctivist. Furthermore,if they deny that there is a common mental element to veridicalperception and hallucination they will satisfy the‘no-common-mental-element’ formulation of disjunctivism.

2.2 Disjunctivism about Intentional Content

According to an intentionalist account of perceptual experience, ourperceptual experiences are mental events (or states) with intentionalcontents that represent the world as being a certain way. Thedisjunctivist who accepts this general approach to perceptualexperience may hold that a veridical perception has an intentionalcontent that a hallucination cannot have. For example this sort ofdisjunctivist may hold that the intentional content of a veridicalperception is constitutively dependent on mind-independent objects,while the intentional content of a hallucination is not.

One route to this view proceeds through the claims that a veridicalperception of the world is a perceptual state with an intentionalcontent containing demonstrative elements that refer to themind-independent items in the environment that are perceived, and thattruth-evaluable intentional contents with demonstrative elements thatsuccessfully refer are object-dependent. On this view, a particularexperienceE that is a veridical perception of a particularmind-independent objectO will have an intentional contentwith a demonstrative element that successfully refers toO,and a distinct particular experienceE^* will havean intentional content with the same veridicality conditions only ifits intentional content contains a demonstrative element that alsorefers toO. IfE^* is a hallucination itwill not have an intentional content with a demonstrative element thatsuccessfully refers toO, so it will not have an intentionalcontent with the same veridicality conditions asE. Supposewe now add the following assumption: If two experiences haveintentional contents which differ in their veridicality conditions,then this is not just a respect in which these mental events differ,it is also amounts to a difference in their mental kinds. We can nowderive the conclusion that veridical perceptions and hallucinationsare experiences of different mental kinds. This last assumption needsto be made explicit, as it is not agreed upon by all (e.g., Burge1993, 2005 and 2010). Note that acceptance of the assumption wouldalso commit one to the following claim: IfE^* is averidical perception of numerically distinct objectO^*, thenE andE^* areto be regarded as experiences of different mental kinds even ifO andO^* are perceptually indiscernibleto the subject who perceives them. (For discussion of the status ofthat assumption, see Mehta 2014, Gomes and French 2016, Mehta andGarson 2016, and French and Gomes 2019).

Someone who holds this sort of view may claim that it is possible fora veridical perception and a hallucination to have the same phenomenalcharacter. For they may claim that it is possible for experiences tohave the same phenomenal character despite the fact that they do nothave the same intentional content. According to the terminology thatByrne and Logue adopt (see section 2.1.2) this would make the viewamoderate one. Someone adopting the moderate approach mightclaim that hallucinations have an existentially quantified intentionalcontent and veridical perceptions also have a layer of content that isexistential. They might then hold that this layer of existentialcontent, which is present in experience whether or not one isveridically perceiving the world, provides a common mental factor forveridical and hallucinatory experiences.

Tye (2007) favours a different ‘moderate’ approach. Heholds that veridical perceptions have object-dependent singularintentional contents that hallucinations cannot have, and he holdsthat veridical perceptions and hallucinations can have the samephenomenal character. However, he rejects the claim that there is alayer of existential content that provides a common mental factor forveridical and hallucinatory experiences. According to Tye, veridicalperceptions and hallucinations have intentional contents thatrepresent clusters of properties. In the case of veridical perceptionthe cluster of properties is represented within a content that issingular and object-dependent, whereas in the case of hallucinationthe cluster of properties is represented within a content that is‘gappy’. (See also Schellenberg 2010, 2013, and 2016.)Tye’s suggestion is that veridical perceptions andhallucinations have contents with a common structure, and thisstructure may be conceived as having a slot in it for an object. Inthe case of veridical perception the slot is filled by the objectperceived, and in the case of hallucination the slot is empty, andhence the content is ‘gappy’. Tye claims that thephenomenal character of a given visual experience is the cluster ofproperties represented by that experience. And he claims that this iswhy veridical perceptions and hallucinations can have the samephenomenal character.

2.3 Disjunctivism about Phenomenal Character

Some disjunctivists claim that veridical perceptions have a phenomenalcharacter that hallucinations cannot possess. For example, accordingto one version of naïve realism (what we might call‘naïve realism about phenomenal character’), when oneveridically perceives the world, the mind-independent items perceived,such as tables and trees and the properties they manifest to one whenperceived, partly constitute one’s conscious experience, andhence determine its phenomenal character. This sort of naïverealist view is primarily motivated by phenomenological considerations.The suggestion is that this view best articulates how sensoryexperience seems to us to be through introspective reflection.According to those who propose this form of naïve realism onecannot provide an adequate account of the phenomenal character ofveridical perception by simply appealing to the idea that suchexperience has an intentional content that represents the world asbeing a certain way, even if one holds that the intentional content inquestion is object-dependent; nor can one provide an adequate accountof the phenomenal character of veridical perception by simply adding tothis the claim that experience possesses further non-representationalproperties that it could possess independently of whether anymind-independent objects are being perceived. The naïve realistabout phenomenal character instead claims that the right account of thephenomenal character of veridical perception should appeal to the ideathat such experience relates to the mind-independent items perceived ina non-representational manner. (The motivations for this view arediscussed in section 3.3).

Since this naïve realist account of phenomenal character cannotbe applied to hallucination, those who propose it are committed to theclaim that the kind of phenomenally conscious experience that occurs whenone veridically perceives the world does not occur when one ishallucinating. These naïve realists can accept that veridicalperceptions of numerically distinct objects can have the samephenomenal character, but they deny that veridical perceptions andhallucinations have the same phenomenal character. They must then saythat hallucinations that are subjectively indistinguishible fromveridical perceptions do not have the kind of phenomenal character thatintrospective reflection suggests. Some disjunctivists allow that somehallucinations that are subjectively indistinguishible from veridicalperceptions have no phenomenal character (e.g., Fish 2008 and 2009; andsee also Sturgeon 2006 and 2008), but this is not a commitment of alldisjunctivists about phenomenal character. (For further discussion, seesection 5.1)

2.4 Epistemological Disjunctivism

Some disjunctivist views are primarily motivated by epistemologicalconsiderations, rather than phenomenological ones. According to oneapproach what is fundamental to the nature of a veridical perception isthe fact that it belongs to an epistemically distinguished class ofperceptual experiences. Those advocating this form of disjunctivismplace emphasis on the idea that when one veridically perceives theworld one has a distinctive form of epistemic contact with themind-independent world, and one’s experience provides one withgrounds for making knowledgeable perceptual judgements about themind-independent world that would be lacking if one were merelyhallucinating. On this view it is a mistake to assume that theepistemic grounds that a veridical perception can provide one with formaking judgements about the world are no better than the epistemicgrounds that are available to one when one has a subjectivelyindistinguishible hallucination. Moreover, according to this view, theepistemic difference between a veridical perception and a subjectivelyindistinguishible hallucination is not to be explained by simply citingfactors that are external to the subjective experiential state one isin when one veridically perceives the world. Rather, the epistemicdifference is due to the fact that the kind of subjective experientialstate one is in when one veridically perceives the world is not thesame as the kind of subjective experiential state one is in when onehas a subjectively indistinguishible hallucination.

Byrne and Logue (2008) and Snowdon (2005a) argue that that this sortof epistemologically motivated view need not preclude the idea that itis possible to identify a perceptual state that is common to veridicalperception and hallucination. The suggestion is that one can accept theclaim that there is an epistemically distinguished category ofexperiential state that can only obtain when one veridically perceivesthe world, and yet one can consistently maintain that it is alsopossible to identify a kind of perceptual state, of which some positiveaccount can be given, which can obtain whether one is veridicallyperceiving the world, or merely having a subjectively indistinguishiblehallucination. One can therefore be an epistemological disjunctivistwithout accepting metaphysical disjunctivism. However, note that if oneholds that the epistemological feature that is present in the case ofveridical perception and lacking in the case of hallucination isfundamental to the kind of mental state it is, then this would make oneafundamental kind disjunctivist (see section 2.1.1).

John McDowell is an epistemological disjunctivist and some havesuggested that the view he espouses does not commit him tometaphysical disjunctivism. (For discussion of this claim see Snowdon2005a, Byrne and Logue 2008, and Haddock and McPherson 2008b). Millar(2007 and 2008) explicitly endorses the claim that we should accept aform of epistemological disjunctivism about perceptual knowledgewithout being committed to metaphysical disjunctivism. (For moregeneral discussion of epistemological disjunctivism, see Pritchard2012, and see also the papers collected in Doyle, Milburn andPritchard 2019).

3. Arguments for Disjunctivism

3.1 An Argument for Disjunctivism as the Default View

When J.M. Hinton first introduced discussion of the disjunctive viewof experience his primary concern was to identify and undermine whathe took to be a substantive assumption in much philosophicaltheorising about perception. His target was the assumption thatveridical perception and subjectively indistinguishible hallucinationhave the same intrinsic nature. In particular, his target was theassumption that the fact that a hallucination can be subjectivelyindistinguishible from a veridical perception is to be explained bythe thesis that these experiences share a common nature that ismanifest to one when has the experiences. Hinton does not try to provedirectly that this ‘common element’ assumption isfalse. Instead, he tries to argue that it is unwarranted, and that hisalternative, disjunctivist approach to perceptual experience should beour default view. M.G.F. Martin has also argued that the disjunctiveaccount of experience should be our default view. Martin’sargument to this effect is discussed in section 3.3. This sectionfocuses on Hinton’s version of the argument.

Hinton (1967 and 1973) develops his disjunctivist view by focusing onthe kinds of reports we make about an experience we are undergoingwhen we are remaining neutral on the question of whether thatexperience is a veridical perception, an illusion, or ahallucination. For example, when making a report about one’sexperience in this neutral way one might say ‘I seem to seeanF’, which can be true whether or not one is actuallyseeing anF, or one might make a claim about what appears toone to be the case. Hinton thinks that those who accept the commonelement assumption will hold that these ‘Neutral ExperienceReports’ are used to pick out the intrinsic properties ofone’s experience, which are manifest to one simply in virtue ofhaving the experience, and which the experience could possess whetheror not one actually perceives anything. Hinton’s alternativeproposal is that these Neutral Experience Reports are equivalent todisjunctive statements of the form ‘I see anF, orI’m having that illusion’. Hinton labels such disjunctivestatements ‘Perception-Illusion disjunctions’. Hintonargues that in order to substantiate their common element assumption,his opponents need to show that our Neutral Experience Reports are notequivalent to these Perception-Illusion disjunctions, and he tries toargue that this is a challenge that his opponents cannot meet.

The fact that Hinton chooses to focus on thereports wemake about our experiences, may be a reflection of the fact that hisprimary concern is to question an assumption about those properties ofexperience that we should be in a position to make reports about simplyin virtue of having the experience. (“You want a predicate whoseapplicability to what is happening in or to me is made clear to me bythe very fact of that thing’s happening”, Hinton 1967,224.) We might then understand Hinton as taking his opponent to becommitted to the claims that (a) perceptions and subjectivelyindistinguishible hallucinations have such properties in common, (b) itis the fact that perceptions and hallucinations have such properties incommon that explains their being subjectively indistinguishible, and(c) these are the properties we are picking out when we make NeutralExperience Reports. He may then be seen as trying to undermine theassumption that (a) and (b) are correct by throwing into doubt ourentitlement to (c).

For Hinton, an important feature of his Perception-IllusionDisjunctions is that they do not report what is happening to thesubject, as distinct from saying, non-committally, that one of a numberof things is happening. Hinton claims that these disjunctive claims donot give a “definite answer” to the question ‘whathappened to the subject?’ or as he sometimes puts it, they do notgive the “what-it-is of the event” in question. This is whyHinton thinks that substantiating the relevant common elementassumption requires showing that our Neutral Experience Reports are notequivalent to his disjunctive statements. According to the thoughtexpressed in (c) above, our Neutral Experience Reports are committal ina way that these disjunctive statements are not. So the idea here seemsto be that if our Neutral Experience Reports are equivalent toHinton’s Perception-Illusion disjunctions, then assumption (c),above, is thereby undermined.

One way of defending a common element view against this line ofargument might be to defend the claim that one can accept (a) and (b)without being committed to (c). Alternatively one might object that anadequate defence of (a) and (b) need not simply depend on establishing(c) (see Snowdon 2008).

Furthermore, one might question what Hinton has in mind in his useof the term ‘equivalent’ when he says that his opponentneeds to show that our Neutral Experience Reports are not equivalent tohis Perception-Illusion disjunctions. For Hinton denies that he issuggesting that his Perception-Illusion disjunctions provide us with aconceptual analysis of our Neutral ExperienceReports. Snowdon (2008) suggests that the most obvious reading of‘equivalent’ in this context is the following:‘P’ is equivalent to ‘Q’ ifand only if it is a priori that necessarily (P if and onlyifQ). Snowdon then poses the following problem forHinton’s argument. The fact that a statement is disjunctive doesnot on its own mean that it cannot be equivalent, in the relevantsense, to a non-disjunctive statement, which, as a consequence ofbeing non-disjunctive, may well count as saying what sort of thing ishappening. Snowdon offers a mathematical example in support of thisclaim. ‘X wrote down a number which is either 2 or anuneven prime number’ is equivalent, in the relevant sense, to‘X wrote down a prime number’.

The problem this poses for Hinton is that it suggests that he may bewrong to assume that his opponent needs to show that our NeutralExperience Reports are not equivalent to his Perception-Illusiondisjunctions. For even if they were equivalent to thePerception-Illusion disjunctions, this might not in itself show thatsuch reports don’t pick out a common element to perception andillusion / hallucination and give a definite answer to the question‘what is happening?’

Snowdon suggests that despite this, what Hinton does achieve, in hisvarious discussions of these issues, is to put pressure on theassumption that there is anything in the use we make of our ordinaryNeutral Experience Reports that thereby commits us to the commonelement view—i.e., the view that Hinton is attempting to target.Suppose we accept that Hinton does achieve what Snowdon suggests.Consistent with this, one might also hold that there is nothing in theuse we make of our ordinary Neutral Experience Reports that therebycommits us to a denial of the common element view. One might think thata denial of the common element view is at least as committal as itsaffirmation, for it involves a substantive metaphysical claim about thenature of perceptual experience. So why should we think that the burdenof proof lies with the common element theorists to establishtheir view?

At points it looks as though Hinton thinks that an extra commitmentincurred by the common element theorist is an epistemic one. Forexample, Hinton considers the following objection that might be raisedagainst his disjunctive approach: “IfA-ing [i.e.,seeing anO] andB-ing [i.e., having that illusion]did not have a worn-on-the-sleeve property in common, how could youtake one for the other?” To which Hinton’s reply is,“Why should it just not seem that they had properties in common?Seeing a flash of light and having the illusion seem, but only seem,to have in common the property ‘whenx occurs a flashof light occurs’” (1967, 225). The implication here seemsto be that Hinton is taking his opponent to be making a substantiveepistemic assumption—that our inability to discern throughintrospection any differences between a hallucination and a perceptionmust ultimately be explained by our positive ability to discernthrough introspection that they are events of the same kind. (For acritique of this assumption, see also Putman 1999).

3.2 An Epistemological Argument

McDowell’s disjunctive conception of perceptual experience isprimarily motivated by epistemological concerns. He appeals to adisjunctive conception of perceptual experience in offering a proposalas to how we should resist a “tempting” line of argumentthat has an epistemological conclusion. The conclusion of the temptingargument is that when one genuinely perceives the world, the epistemicgrounds one has for one’s world-directed judgements can be nobetter than those available to one when one hallucinates. (See McDowell1982, 1987, 1994, 2008, 2010, and 2013. See Putnam 1999 for an endorsement ofMcDowell’s approach.)

The tempting line of argument that McDowell is concerned to resiststarts by proposing that since hallucinations can be subjectivelyindistinguishible from genuine perceptions, the differences betweenyour genuine perceptions and your hallucinations must be external tohow things are with you subjectively. An epistemic claim is then made:Matters external to how things are with you subjectively cannotintelligibly contribute, even in part, to your epistemic standing onsome question. For such matters will be beyond your ken, and mattersbeyond your ken cannot make any difference to your epistemic standing.The conclusion that is then drawn is that when you genuinely perceivethe world your epistemic grounds for making world-directed perceptualjudgements are the same as, an hence no better than, those available toyou when you have a subjectively indistinguishible hallucination.

In responding to this line of argument, McDowell appeals to adisjunctive conception of perceptual experience in order to block themove from the claim that (i) hallucinations can be subjectivelyindistinguishible from genuine perceptions, to the claim that (ii) thedifferences between a genuine perception and a hallucination must be“blankly external to one’s subjectivity” (McDowell1982). This is then supposed to provide us with a way of resisting theargument’s conclusion—i.e., the claim that the experiencesinvolved in genuine perception and hallucination do not differ in theirepistemic significance. According to the disjunctive conception ofexperience that McDowell proposes, we can accept that what is common toa genuine perception and a subjectively indistinguishible hallucinationis the fact that the subject’s experience is such that it appearsto her that some environmental fact obtains. However, we should alsoaccept that an appearance that such-and-such is the case can beeither a mere appearanceor the fact thatsuch-and-such is the case making itself perceptually manifest tosomeone, and on McDowell’s view, when a fact is made perceptuallymanifest to one, the obtaining of the fact is not “blanklyexternal to one’s subjectivity”. So the obtaining of thefact can contribute to one’s epistemic standing.

A standard line of objection against McDowell’s disjunctivistproposal is that the epistemological considerations he invokes do notadequately support the disjunctive account of experience that herecommends. The general claim behind this line of objection is that anadequate account of the epistemological role of perceptual experienceneed not involve any appeal to disjunctivism. As there are manydifferent accounts of the epistemological role of perceptualexperience, there are many different forms that this line of objectioncan take.

For instance, according to one widely held view, the perceptualjudgements one makes when one is having a perfect hallucination can bejustified and have the same justificatory status as the perceptualjudgements one makes when one genuinely perceives the world. Accordingto this view, there is a sense, then, in which the conclusion of thetempting line of argument that McDowell considers is true: when yougenuinely perceive the world your epistemic grounds for makingworld-directed perceptual judgements are the same as, an hence nobetter than, those available to you when you have a subjectivelyindistinguishible hallucination. However, those who accept this claimmay deny that this puts into jeopardy the common sense idea that whenwe do succeed in perceiving the world we usually do acquirenon-inferential, world-directed, perceptual knowledge. For they mayclaim the epistemic difference between a veridical perception andhallucination is not to be explained by appealing to some difference inthe justificatory status of the judgements that such experiences giverise to. The epistemic difference is, rather, to be explained byappealing to the fact that when one perceives the world some furtherconditions required for perceptual knowledge will usually be met.

Taking this line might be one way of resisting an epistemicassumption made in the “tempting” line of argument thatMcDowell considers, namely the assumption that matters external to howthings are with you subjectively cannot intelligibly contribute, evenin part, to your epistemic standing on some question. An alternativeway of resisting this epistemic assumption is to accept a viewaccording to which matters external to how things are with yousubjectively can contribute to the justificatory status of yourbeliefs. (For an example of this approach to justification, see Goldman1979).

According to another line of objection, one that is more sympatheticto McDowell’s general epistemological outlook, one can resist thetempting line of argument in a way that closely parallelsMcDowell’s proposal, but without being committed to a disjunctiveview of appearances. Williamson (2000) proposes a view of this kind.According to this view, when one genuinely perceives the world and seesthat such and such is the case, one is in a factive mental state ofknowing that such and such is the case. This factive mental state canonly obtain when one is veridically perceiving the world, and it cannotobtain when one is hallucinating. Furthermore, this factive mentalstate is not to be given a conjunctive analysis. It is not to beregarded as being in a state that can be conjunctively analysed interms of having an experience that such and such is the case, plus somefurther, extra-mental conditions that are ‘blankly external toone’s subjectivity’. So the proponent of this view agreeswith McDowell that when one sees that such and such is the case one isin a distinctive kind of mental state that cannot be conjunctivelyanalysed. However, the proponent of this view rejects McDowell’sclaim that one should give a disjunctive account of appearances. Foraccepting that one cannot give a conjunctive analysis ofseeing that such and such is case is compatible with sayingthat itsappearing to one that such and such is the case is amental state common to genuine perception and hallucination, where sucha state is not to be given a disjunctive characterisation. (For furtherdiscussion of this line of objection, see section 4.3)

A further criticism that has been levelled against McDowell’sproposal is that his disjunctive account of experience fails to bringwith it the epistemic benefits that he advertises it as having.McDowell has suggested that in showing how the disjunctive account herecommends allows us to resist the tempting line of argument that heconsiders, he has shown us how to “remove a prop” uponwhich a certain line of sceptical argument depends. (In particular,see McDowell 2008). Against McDowell, Wright (2002, 2008) argues thatdisjunctivism provides us with nothing to address mainstreamperceptual scepticism. Wright claims that the traditional Cartesiansceptical argument does not rely on the impossibility of directperceptual acquaintance with the world. It allows that you may behaving a perceptual experience that involves a fact in the worldmaking itself perceptual manifest to you. What it attempts toundermine is the idea that anything other than agnosticism as towhether or not you are perceiving is warranted, even in thissituation. (See also Conee 2007, and Byrne 2014.)

In response to this criticism, McDowell has said that in acceptinghis disjunctive account of experience we need not pretend to have anargument that can prove that we are not being deceived using premiseswe can affirm without begging the question against the sceptic. Whatthe disjunctive account does achieve, though, is to show we can resistsceptical arguments that appeal to the “highest commonfactor” conception of experience—that conception ofexperience according to which genuine perceptions and subjectivelyindistinguishible hallucinations do not differ in their epistemologicalsignificance. For the disjunctive account of experience blocks theinference from subjective indistinguishability to the highest commonfactor conception. According to McDowell’s diagnosis, the movefrom subjective indistinguishability to the highest common factorconception depends upon an illegitimate view of self-knowledge. (For asimilar proposal see Williamson 2000). And McDowell argues that thisillegitimate view of self-knowledge itself makes unintelligible acharacteristic of experience that the sceptical argument does notusually question—that our perceptual experience at leastpurports to reveal how things are in the objective world.

So an important element of McDowell’s disjunctive approach is hisopposition to a certain view of self-knowledge. (See especiallyMcDowell 1987.) According to the view he opposes, although yourability to tell how things are in the world by looking is fallible,your ability to tell how things are with you subjectively isinfallible, in the following sense: the truth about how things arewith you subjectively is infallibly accessible to your capacity toacquire knowledge on such matters.This picture of self-knowledge isincompatible with the disjunctive account of experience that McDowellrecommends. According to that disjunctive account when you have anexperience, you can know, independently of whether you know that youare hallucinating, that it appears to you that such and such is thecase. However, its appearing to you that a such and such is the casecan be either a situation in which a fact in the environment is beingmade perceptually manifest to you, or a situation that involves a mereappearance, and you cannot know which disjunct obtains independentlyof knowing whether you are hallucinating. According to McDowell, whena fact is made perceptually manifest to you, the obtaining of the factis not “blankly external to your subjectivity”. Theresultant view is incompatible with the claim thatall of thetruths about how things are with you subjectively are infalliblyaccessible to you. For if all of the truths about things are with yousubjectively were infallibly accessible to you, your capacity to knowwhether or not you were hallucinating would also be infallible.

For discussion of McDowell’s disjunctivism, see Neta 2008,Pritchard 2008, Sedivy 2008, Brogaard 2011 and Haddock 2011. Forfurther discussion of McDowell’s disjunctivism and comparisonwith Austin 1962, see Thau 2004, and for discussion of whether Austinwas a disjunctivist, see also Longworth 2014. For discussion ofepistemological disjunctivism in general, see Pritchard 2012, Sedivy2019, French 2016 and 2019, Mitova 2019, Littlejohn 2019, Neta 2019,and Haddock 2019.

3.3 A Phenomenological Argument

Martin argues for a naïve realist account of the kind ofexperience one has when one genuinely perceives the world. According tothis naïve realist account, when one genuinely perceives the worldone is directly aware of mind-independent objects and their features.Furthermore, according to this view, when one perceives the world, theactual objects of perception, the external things such as trees, andtables, which one can perceive, and the properties they manifest to onewhen perceived, partly constitute one’s conscious experience, andhence determine its phenomenal character. (See Martin’sdiscussion of naïve realism in his 1997, 1998, 2002, 2004, and2006.) Since one is not aware of mind-independent objects and theirfeatures when one hallucinates, the naïve realist cannot offer thesame account of the phenomenal character of hallucinations. Thenaïve realist is committed, then, to the claim that the kind ofphenomenally conscious episode that occurs when one perceives the worldis not one that could be occurring were one hallucinating. So in orderto preserve his naïve realist account of the phenomenal characterof genuine perceptions, Martin advocates a disjunctive account ofperceptual experience. According to Martin, genuine perceptions andintrospectively indiscriminible hallucinations are not mental events ofthe same fundamental kind.

Martin’s naïve realist account of genuine perception ismotivated by phenomenological considerations. He argues thatnaïve realism best articulates how sensory experience seems to usto be through introspective reflection. If introspective reflectionsupports a naïve realist account of the phenomenal character ofgenuine perceptions, then presumably introspective reflection shouldlend the same support to a naïve realist account of thephenomenal character of hallucinations that are introspectivelyindiscriminible from genuine perceptions. Since the naïve realistaccount of phenomenal character cannot be applied to hallucinations,the naïve realist must then say that hallucinations that areintrospectively indiscriminible from genuine perceptions do not havethe phenomenal character that introspective reflectionsuggests—they do not have the phenomenal character that theyintrospectively seem to us to have. However, if Martin is right in hisclaim that introspective reflection supports naïve realism, thenif we reject naïve realism, we will have to acceptthatall perceptual experiences, whether genuine perceptionsor hallucinations, fail to have the phenomenal character thatintrospective reflection suggests. (For a similar proposal, see alsoLangsam 2017).

As Martin sees it, then, the dialectical position is this: thedisjunctivist naïve realist allows that at least some of ourperceptual experiences really do have the phenomenal character thatthey introspectively seem to have—namely the genuineperceptions—whereas the opponent of naïve realism needs todeny that any of our perceptual experiences really do have thephenomenal character that they introspectively seem to have. So Martinadvocates the disjunctivist naïve realist view as the best errortheory concerning perceptual experience and the introspection ofexperience.

The claim that when one genuinely perceives the world one isdirectly aware of mind-independent objects and their features is notdistinctive of the naïve realist account. For example, someonewho holds an intentionalist account of experience can also accept thisclaim. According to this view our perceptual experiences are mentalstates with intentional contents that represent the world as being acertain way, and when one has an experience with a veridical content,in the right circumstances, one is directly aware of mind-independentobjects in one’s environment. (Advocates of such intentionalistaccounts of experience include Searle (1983), Harman (1990), Tye(1992, 1995, and 2000), Burge (1993 and 2010), Dretske (1995), Byrne(2001), and Pautz (2010)). Many have argued that this sort of theorycan adequately accommodate the phenomenological aspects of experiencethat a naïve realist might point to—e.g., the apparentpresence to mind of mind-independent objects and theirfeatures—without being committed to the idea that hallucinationsfail to have the phenomenal character that they introspectively seemto have.

Martin (2002) compares and contrasts the intentionalist and naïverealist accounts of these phenomenological aspects of perceptualexperience and argues that introspective reflection on the nature ofsensory imagination—in particular, visualising— gives usreason to support the naïve realist account over theintentionalist one. Martin’s argument for this claim has the followingstructure: (i) He compares and contrasts the naïve realist andintentionalist accounts of certain aspects of the phenomenology ofperceptual experience—their transparency and immediacy. (ii) Heargues for a thesis about visualising—the ‘dependencythesis’, which states that to visualise anF is toimagine a visual experience of anF. (For an influentialdiscussion of this idea, see Williams 1973. For an endorsement of theview, see Peacocke 1985 and Vendler 1984.) (iii) He argues that thetruth of the dependency thesis should lead the intentionalist and thenaïve realist to make different predictions about thephenomenology of visualising, given their different accounts of thetransparency and immediacy of perceptual experience. So, he claims,the phenomenology of visualising can be regarded as a test of thesecompeting views. (iv) He argues that the phenomenology of our episodesof visualising favours the naïve realist account.

The particular phenomenological aspects of perceptualexperience—transparency and immediacy—that the naïverealist and the intentionalist try to accommodate in different ways,are the following.Transparency: When one attends to what itis like for one to have a visual experience it seems to one as thoughone does so through attending to mind-independent objects in one’senvironment andtheir features.Immediacy:Furthermore, our perceptual experiences are non-neutral about theactual presence of the mind-independent objects and features in ourenvironment they are directed upon. They appear to have a coercivepower and authority over our beliefs. Even if one believes that one ishallucinating, the phenomenal immediacy of the experience—itsnon-neutrality about the actual presence of mind-independent objectsand features in our environment—is not thereby extinguished.Intentionalists can explain the transparency and immediacy ofperceptual experience in terms of the idea that (a) perceptualexperiences are mental states with intentional contents that representthe mind-independent world as being a certain way (hencetransparency); and in terms of the idea that (b) such states play adistinctive kind of functional role in our mental economy (henceimmediacy). This is not the account offered by the naïverealist. For the naïve realist, one’s experience relates to theworld in a non-representational manner. According to the naïverealist, the transparency and immediacy of genuine perceptions areexplained in terms of the idea that mind-independent objects and theirfeatures are constituents of one’s perceptual experience thatdetermine, at least in part, the phenomenal character of thatexperience. The phenomenal transparency and immediacy of ahallucination is explained derivatively—in terms of its beingintrospectively indiscriminible from something it is not—amental event with the phenomenal character of a genuineperception.

On the face of it, the intentionalist appears to be able toaccommodate adequately the transparency and immediacy of experiencewithout committing to the idea that hallucinations fail to have thephenomenal character that introspective reflection suggests. This mightlead one to favour the intentionalist view. However, Martin argues thatreflecting on the phenomenology of visualising gives us reason to thinkotherwise.

Martin argues that in order to capture adequately the respect in whichthe phenomenology of visualising anF has some correspondencewith the phenomenology of having a visual experience of anF,we should accept the dependency thesis—the thesis that tovisualise anF is to imagine a visual experience ofanF. He then argues that the truth of the dependency thesisshould lead the intentionalist and the naïve realist to makedifferent predictions about the phenomenology of visualising. Martinargues that if the dependency thesis is correct, then theintentionalist should hold that when we visualise, we imagine a mentalstate (i.e., a visual experience) that represents the world to be acertain way and that has a distinctive kind of functional role. Wemay, as part of our imaginative project, suppose that the imaginedsituation contains the objects and features represented by theimagined visual experience, but, argues Martin, the intentionalistshould predict that (a) when one visualises something, e.g., an apple,the imagistic character of one’s visualising should itself be neutralwith respect to whether or not one is imagining a scene that containsan apple, and (b) something other than the putative object ofexperience (i.e., the apple) should be available to introspection. Therepresentational properties of the experience one is imagining shouldbe revealed to one as such.

According to Martin, as the naïve realist offers a ratherdifferent account of the phenomenal transparency and immediacy ofvisual experience, the naïve realist should make rather differentpredictions about the phenomenology of visualising. According to thenaïve realist, a visual experience of an apple seems to itssubject to beconstitutively dependent on the presence of theapple. So given the truth of the dependency thesis, the naïverealist should predict that when one visualises an apple, theimagistic character of one’s visualising won’t be neutralwith respect to whether or not one is imagining a scene that containsan apple. It should be committal on the presence of an apple in theimagined scene. Martin claims that the actual phenomenology ofvisualising is more in keeping with what the naïve realistpredicts. He argues that as introspective reflection best supports thenaïve realist prediction, we can either deny naïve realismand hold that none of our perceptual experiences have the phenomenalcharacter that introspective reflections suggests, or we can accept anaïve realist account of genuine perceptions and hold that onlysome of our perceptual experiences fail to have the phenomenalcharacter that introspective reflection suggests. This latterposition, according to Martin, is the least revisionary option.

One line of objection against Martin’s argument targets thedependency thesis. For example, Noordhof (2002) and Burge (2005)question the plausibility of a claim that appears to be a commitment ofthe dependency thesis: that in visualising an object one must beimagining a perceptual experience of the object, despite the fact thatimagining the experience may have been no part of your imaginativeproject. Some opponents of the dependency thesis have argued that thecorrespondences between visual experience and visualising are to beaccounted for by the fact that there are similarities in therepresentational contents of these episodes. (See Noordhof 2002 andCurrie and Ravenscroft 2002.)

An alternative response to the argument may be to accept thedependency thesis, but to question whether introspective reflectionreally does support the claim that the imagistic character ofvisualising an apple is itself non-neutral with respect to whether theimagined scene contains an apple. It might be held instead that thephenomenology of an episode of visualising does not speak to suchmatters independently of the question of what suppositions the subjectis making in engaging in his imaginative project (see Burge 2005).Alternatively, one might raise a more general scepticism about thereliability of appeals to introspection in supporting claims about thereal nature of perceptual experiences (see Spener 2003). Some may holdthat since we must allow that hallucinations do not have the sort ofphenomenal character that introspective reflection suggests, there islittle additional cost in allowing that veridical perceptions alsofail to have the phenomenal character that introspective reflectionsuggests. (For critical discussion of Martin’s argument, seealso Dorsch 2010.)

3.4 An Argument from Epistemic Modesty

According to Martin, properly understood, disjunctivism offers us anepistemological perspective on how we should conceive of debates aboutperceptual experience. Martin suggests that the key to the disjunctiveapproach lies not in its appeal to paraphrasing claims about experiencein disjunctive form, but rather in its appeal to the epistemic notionofindiscriminability in explicating the claims we make aboutperceptual experience. (For detailed discussion of the notion ofdiscriminability, see Williamson 1990). Martin suggests that what isdistinctive of the disjunctive approach is the ‘modesty’ ofthe claims it makes about what one can know about one’sperceptual experiences. In contrast, the alternatives to thedisjunctive approach are ‘immodest’ in their assumptionsabout our epistemic powers. The alternatives to the disjunctiveapproach that Martin appears to have in mind here are those versions ofthe common element view that hold that (a) there are phenomenalproperties that are common to perceptions, illusions, andhallucinations, and (b) the possession of such properties is bothnecessary and sufficient for an event to be a conscious perceptualexperience.

Martin’s argument for the claim that the alternatives to thedisjunctive approach incur greater epistemic burdens primarily focuseson our understanding of the notion of a perfect hallucination.Sceptical arguments often introduce talk of ‘perfecthallucinations’. On one understanding such talk is taken tobe introducing the notion of a conscious mental event that is not agenuine perception but which is introspectively indiscriminible from agenuine perception of the world. An assumption oftenmade is that such an experience would have the same phenomenalproperties as some possible genuine perception. But from the fact thata conscious mental event is introspectively indiscriminible from agenuine perception, does it follow thatmust have the samephenomenal properties as a genuine perception?

Suppose we answer that this does not follow—i.e., we accept thatit may be possible, in principle, for there to occur a consciousmental event that is introspectively indiscriminible from a genuineperception, but which does not have the same phenomenal properties asa genuine perception. Should we say that such events count asperceptual experiences? If one denies that such mental events shouldbe regarded as perceptual experiences, then, Martin suggests, one owessome kind of justification for this denial, for this stance on what isrequired for a mental event to be a perceptual experience will seem,from a common sense perspective, to be too restrictive. On the otherhand, if one holds that such mental events should be regarded asperceptual experiences, then this suggests that our most inclusivenotion of what it is for something to be a perceptual experience is anepistemic one—that of being introspectively indiscriminible froma genuine perception—which does not involve the furthermetaphysical assumption that perceptual experiences which aren’tgenuine perceptions must have the same phenomenal properties asgenuine perceptions.

Now suppose instead that we say that if a conscious mental event isintrospectively indiscriminible from a genuine perception it has thesame phenomenal properties as a genuine perception. According to Martinthis would be to embrace a substantive epistemic principle. For inadopting this stance one would be committed to the epistemic claim thatin the case of any conscious mental event that lacks the phenomenalproperties of a genuine perception, the fact that it lacks the relevantphenomenal properties will be something that is knowable throughintrospection. According to such a view, it is not just that thephenomenal properties that determine an event as an experience are heldto be introspectively detectible and recognisible as such when present.It must also be the case that the absence of such properties, when theyare absent, is equally detectible through introspection.

According to Martin, given that this approach to perceptualexperience needs to rely on this epistemic assumption, it carries moretheoretical burdens than does the more “modest”disjunctivist approach. For when it comes to characterizing the notionof perceptual experience in general, the disjunctive approachemphasizes thelimits of our powers of discrimination, ratherthan appealing to a substantive condition that an event must meet to bean experience, and in addition ascribing to us cognitive powers torecognize the presence of this substantive condition. So, according to Martin, theburden is really on the common element theorist, either to show thatthe extra epistemic commitment is one we should accept, oralternatively, to justify the claim that those conscious mental eventsthat are introspectively indiscriminible from genuine perceptions butwhich lack the phenomenal properties of genuine perceptions should notbe regarded as a perceptual experiences. This argument does not purportto show that the common element view is wrong, but rather to show thatthe default position should be that of the disjunctivist.

Various objections have been raised against Martin’s proposal.Some object to Martin’s suggestion that being subjectivelyindiscriminible from a genuine perception is a sufficient conditionfor being a perceptual experience. Siegel (2004 and 2008), Hawthorneand Kovakovich (2006), Smith (2008), and Byrne and Logue (2008) pushthis line of objection. In effect, such objectors may be seen asattempting to meet one of Martin’s challenges by offering reasonto think that our notion of perceptual experience is, after all, morerestrictive than the epistemically characterised one he proposes.Siegel objects that a cognitively unsophisticated creature, such as adog, will be incapable of introspectively discriminating theexperiences they have. So we cannot appeal to the notion of subjectiveindiscriminability in our account of what makes it the case that thedog has a perceptual experience of anF. Byrne and Logue(2008) and Smith (2008) object that even in the case of a cognitivelysophisticated subject we should not rule out the possibility of theoccurrence of a conscious mental event that is not a perceptualexperience, but which is subjectively indiscriminible from a veridicalperception. For example, it might be argued that we should deny thatepisodes of perceptual imagining (e.g., visualising) are perceptualexperiences, and we should allow that it may be possible for anepisode of visualising to be subjectively indiscriminible from averidical perception. One might think that just such episodes occurwhen one is dreaming. (For example, see Ichikawa 2009). Keith Allen(2015), on the other hand, argues that hallucinations are degeneratekinds of sensory imagination and that the view that hallucination is akind of sensory imagination represents a promising account ofhallucination from the perspective of a naïve realist theory ofperception like naïve realism.

If one does allow that conscious mental events of different kinds(e.g., perceptual experiences and perceptual imaginings) can beintrospectively indiscriminible, then it seems that one’s defenceof the claim that perfect hallucinations and genuine perceptions areevents of the same fundamental kind cannot simply appeal to the factthat they are introspectively indiscriminible. One might, nonetheless,think that there is introspective support for the claim that genuineperceptions have phenomenal properties which are such that (i) anevent’s possession of them is independent of the conditions ofperception, and (ii) an event’s possession of them is sufficientto account for the fact that the event is introspectivelyindiscriminible from a genuine perception. One might then simply define‘perfect hallucinations’ as those experiences that are notgenuine perceptions, but which have the same phenomenal properties asgenuine perceptions. (See section 3.3 for discussion of Martin’spositive argument for Naïve Realism, which can be seen as anattempt to challenge such claims.)

According to another line of objection, Martin is wrong to proposethat being introspectively indiscriminible from a genuine perception isa necessary condition for being a conscious perceptual experience. Foralthough being introspectively indiscriminible from a genuineperception may be a condition satisfied by all genuine perceptions andperfect hallucinations had by subjects capable of makingintrospective judgements about their perceptual experiences, it is nota condition that need be satisfied by other perceptualexperiences. For instance, Siegel (2004) argues that experiences as ofimpossible scenes—e.g., experiences as of certain Escherscenes—do not satisfy this condition.

Siegel (2004) also suggests that, properly understood, the epistemicburden incurred by the common element theorist is not so great afterall, as it leaves open the possibility that subjects may make all kindsof mistakes about the kinds of experiences they are having. One’sview on whether or not the epistemic commitment that is beingattributed to the common element theorist by Martin is excessivelyburdensome may depend, in part, on how one understands the notion ofintrospective indiscriminability in play in his argument. This may alsoaffect how plausible one finds the claim that being introspectivelyindiscriminible from a genuine perception is necessary and sufficientfor being a perceptual experience. Martin’s views on these issuesare discussed further in section 5.1.

3.5 An Argument from Demonstrative Reference

John Campbell (2002a, 2002b, 2005, 2011) has argued that there isan important connection between the nature of the conscious perceptualexperience that occurs when we veridically perceive the world and ourability to think demonstratively about the mind-independent objectsthat we perceive. He argues that only a ‘relational view ofexperience’ can adequately acknowledge the role of consciousexperience in making it possible for us to think demonstratively aboutthe categorical properties of the mind-independent objects weperceive, and this relational view of experience commits him to a formof disjunctivism about perception.

According to this relational view of experience, when you veridicallyperceive the world the mind-independent objects and properties youperceive are constituents of your conscious experience—thequalitative character of the conscious experience you undergo isconstituted by the qualitative characters of the mind-independentitems you perceive. This kind of experience cannot occur when youhallucinate—veridical perceptions and hallucinations areexperiences of different conscious kinds—hence the commitment todisjunctivism. More precisely, according to the relational view ofexperience that Campbell endorses, we are not to think of perceptualconsciousness of an object as a two-place relation between a personand an object, but rather as a three-place relation between a person,astandpoint, and an object. Campbell suggests that we needto factor in the notion of a ‘standpoint’ as ourexperience of objects is always in some sense partial. You alwaysexperience an object from a standpoint, and you can experience one andthe same object from different standpoints. (For a similar proposal,see Brewer 2011 and 2017a. For further discussion of this aspect ofnaïve realism, see French 2018 and Christy 2019).

Campbell argues that an adequate account of the nature of ourconscious experience of objects should accommodate the fact that suchconscious experience performs a significant explanatory role. Accordingto Campbell, such conscious experience provides us with knowledge ofwhat our perceptual demonstrative terms, like ‘this’ and‘that’, refer to. Furthermore, according to Campbell, theknowledge of the semantic value of the demonstrative that suchconscious experience provides us with, justifies and causes the patternof use we make of that demonstrative in our reasoning. The relevantpatterns of reasoning we engage in reflect our conception of the objectreferred to as mind-independent. So, Campbell argues, our consciousexperience of objects has a role to play in explaining what provides uswith our conception of the objects of perception as mind-independent.Campbell argues that it is only the relational view of experience thatcan adequately acknowledge the way in which conscious experience playsthis explanatory role, so competing accounts of experience should berejected.

Note that the explanatory role that Campbell is suggesting that ourconscious experience of objects is supposed to play isn’t simply thatof justifying, or providing warrant for, our beliefs and judgementsthat employ perceptual demonstratives. His claim is rather that suchexperience has a role to play in justifying the patterns of use wemake of the demonstrative in reasoning that we engage in—wheresuch reasoning reflects our grasp of the criteria of identity of theobject referred to, which in turn reflects our grasp of the object asbeing mind-independent. According to Campbell, this pattern of use isjustified by appeal to the semantic value of the demonstrative. Ourconscious experience of the object to which the demonstrative refersprovides us with a form of knowledge of the semantic value of thedemonstrative, and thereby plays a role in justifying the use we makeof the demonstrative in our reasoning.

Campbell argues that one cannot adequately acknowledge the way inwhich conscious experience plays this explanatory role if one holds aview of experience according to which an experience is a mental stateor event with an intentional content that represents the world asbeing a certain way. For such a view of experience at best presupposeswhat is to be explained. It presupposes what is to be explained if thecontent of such a representational state is conceptual, and it doesn’thave the resources to play the relevant explanatory role if itsrepresentational content is non-conceptual. What’s required, arguesCampbell, is a conception of experience as something less thanconceptual representation of the object of experience, but whichnonetheless has the resources to explain how experience of an objectcan provide one with a form of knowledge of the semantic value of ademonstrative that refers to it. Campbell argues that the onlyadequate contender is the relational view, for according to therelational view one’s conscious experience in the veridical caseacquaints one with a mind-independent object and itscategorical properties. This confrontation with, this awarenessof, the mind-independent object referred to is what providesone with the relevant form of knowledge of the semantic value of thedemonstrative that allows experience to play its explanatory role.

As Campbell himself points out, his argument presses very hard theidea that experience of objects has this explanatory role to play. Someissues of contention here are the following: (a) Whether an account ofthe nature of conscious experience really does have a role to play whenit comes to an explanation of the fact that we have a conception ofobjects in the world as mind-independent. (b) If the nature ofconscious experience does have such an explanatory role to play,whether it is the one that Campbell identifies—i.e., that ofcausing and justifying the use we make of demonstrative terms thatrefer to the mind-independent objects we perceive. (c) Whether therelational view of experience really does have the resources to playthe explanatory role that Campbell assigns to it. (For criticism ofCampbell’s argument, see Burge 2005, Rey 2005, and Cassam 2011).

3.6 Further Motivations for Disjunctivism

This section briefly summarises some further considerations thathave been appealed to in motivating disjunctive accounts of perceptualexperience.

Some have argued that a genuine perception of the world is aperceptual state with an intentional content containing demonstrativeelements that refer to the items perceived. (See Brewer 2000, Burge1993, and Tye 2007, Scellenberg 2010, 2013, and 2016. For objectionsto this idea see Davies 1992 and McGinn 1982.) Acceptance of thisview, together with two further assumptions, can lead to theconclusion that the kind of experience that occurs when one perceivesthe world isn’t one that can occur when one hallucinates, whichin turn can motivate a disjunctive approach to perceptual experiencein general. The two further assumptions are the following. (a)Truth-evaluable intentional contents with demonstrative elements thatsuccessfully refer are object-dependent, and (b) experiences are ofthe same mental kind only if they have the same truth-evaluablecontents. (The latter claim is endorsed by Evans 1981, 1982 andMcDowell 1984. For criticisms of this claim see Burge 1983, 1993,2005, 2010, and Martin 2003).

Brewer advocated a view of this form in his bookPerception andReason. In his more recent work on perceptual experience he hasproposed an alternative view of genuine perception, but which alsocommits to disjunctivism about perceptual experience. (See Brewer2004, 2006, 2008, 2011, 2017a, and 2017b.) In this work Brewer isconcerned to identify and defend the account of experience that hethinks is most conducive to our common sense ‘empiricalrealist’ world-view—the view that the tables, trees,people and animals etc, that we sense, are as they are independentlyof anyone’s thought or experience of them. Brewer argues thatthe ‘Object View’ of experience, which he contrasts withthe ‘Content View’, is the most promising suchaccount. According to this ‘object view’, perception is anacquaintance with mind-independent empirical things whose basicnatures and perceptible qualities constitute what it is like to bepresented with them in this way. A similar line of empirical realistline of thought can be found in Campbell’s work. (For example,see Campbell and Cassam 2014. For a related line of thought, see alsoLogue 2012b). Campbell argues that only a naïve realist account of thephenomenal character of perception can accommodate an epistemic rolethat conscious perception plays in grounding the concepts we possessof mind-independent objects and the qualities we perceive. Forexample, he argues that only a naïve realist account of phenomenalcharacter can adequately capture the following two ideas: (i) Thephenomenal character of perception plays a crucial role in explainingour distinctive conceptions of what our colour terms refer to, and(ii) our colour terms refer to mind-independent qualities ofobjects. (For discussion of Campbell’s view, see Soteriou 2016,Ch. 4. For objections to Campbell’s arguments, seeCassam’s contribution to Campbell and Cassam 2014. Forobjections to the view of colour defended by Campbell, see Pautzforthcoming. For further discussion of this issue, see Kalderon 2011,Allen 2016, and Beck 2019).

One significant recent source of motivation for disjunctivism (commonto the views proposed by Martin, Campbell and Brewer) is thesuggestion that we should moving away from representationalistaccounts of the way in which our minds are intentionally directed uponthe mind-independent world when we perceive it. Influential in thisregard is Charles Travis’s work on perception. Travis (2004 and2013), who cites Austin’sSense and Sensibilia as animportant influence, argues that perception is notrepresentational. He offers a critique of a representationalist viewthat is committed to the following claims: (i) Experiences haverepresentational contents and can be true / false—veridical/non-veridical; (ii) the representational content of an experience issomething that the subject can take at face value, and accept, ordecline; (iii) the experience having this content isn’t a matterof the subject taking / judging things to be a certain way; and (iv)the way our experience represents things to be is something we canappreciate and recognize. According to Travis’s alternative viewof perception our senses confront us with what is there, they bringour surroundings into view, but there is nothing in a perceptualexperience to make it count as having some one representationalcontent as opposed to countless others. In making out, or trying tomake out what it is that we are confronted with,we may go wrong, and make false judgements, but when we aremisled in this way, this is not because our senses non-veridicallyrepresent to us that the world is a certain way. On the assumptionthat we are not confronted with the mind-independent world when wehallucinate, this sort of view naturally leads to a disjunctivist viewof perceptual experience. (For discussion of these issues, see Raleigh2013, Shahmoradi 2016, and Wilson 2018).

4. Objections to Disjunctivism

Some of the objections raised against disjunctive theories aredirected at the specific arguments proposed in support of differentversions of disjunctivism. For discussion of objections to thearguments proposed by Hinton and McDowell, see sections 3.1, and 3.2;and for objections to arguments proposed by Martin see sections 3.3and 3.4. For objections to disjunctivist accounts of hallucination,see section 5. Some arguments against certain versions ofdisjunctivism are directed against what are taken to be some of themetaphysical commitments of the naïve realist account of veridicalperception. For example, Pautz (forthcoming) argues that naïve realismabout veridical perception carries commitments about the metaphysicalstatus of observable qualities, such as colour, that are undermined byempirical science. This section discusses arguments aimed at a moregeneral level, against the disjunctivist’s denial that veridicalperceptions, illusions and hallucinations are mental events of thesame fundamental kind, and in favour of the view that there is commonelement to veridical perception, illusion and hallucination.

4.1 The Explanatory Power of the Common Kind Claim

Sturgeon (1998) offers a number of reasons for thinking that ourdefault view should be the thesis that there is a common factor toveridical perceptions, illusions and hallucinations—i.e., thethesis that they all involve perceptual states of the same basickind—rather than the disjunctivist view.

Sturgeon points to a number of features that can be common toveridical perceptions, illusions, and hallucinations. Among thefeatures he points to are the following: (i) veridical perceptions,illusions and hallucinations can produce similar behavioural effects.For example, in general, if it sensibly appears to you as though arock is flying towards you, you will duck, irrespective of whether theexperience you are having is a veridical perception, an illusion, or ahallucination. (ii) If, on the basis of that experience, you believethat a rock is flying towards you, and you act on that belief andduck, there is a sense in which your belief and action are rational,irrespective of whether that experience is a veridical perception, anillusion, or a hallucination. (iii) If you have an experience as of arock flying towards you, you can know what it’s like to see a rockflying towards you, irrespective of whether that experience is averidical perception, an illusion, or a hallucination. (iv) Veridicalperceptions, illusions and hallucinations can be introspectivelyindistinguishible.

Sturgeon suggests that the most obvious explanation of the fact thatthese experiences share these features is the proposal they all involvemental states of the same kind. So this should be our default viewuntil we are given reason to be persuaded otherwise.

The disjunctivist may try to explain the fact that illusions andhallucinations can have the same kinds of behavioural effects asveridical perceptions by simply appealing to the fact that suchexperiences can be subjectively indistinguishible from veridicalperceptions. Since the difference between a hallucination and averidical perception may be something that a subject is unable todetect through introspection, the hallucination will naturally giverise to effects that are similar to those of the veridical perception.The subject will respond to such a hallucination in the same kind ofway in which she would respond to a veridical perception. And there is asense in which this response can be regarded as rational.

However, the disjunctivist who denies that a hallucination can havethe same phenomenal character as a veridical perception will be putunder pressure to offer some positive explanation of the fact that ahallucination can seem to have the same phenomenal character as averidical perception, and in particular, to offer some explanation ofhow it is that a subject can come to know what it is like to have averidical perception of anF through simply having ahallucination of anF, given that the hallucination does notactually possess the what-it-is-like properties of the veridicalperception. As Hellie (2007) notes, while noteverything isthe way it appears, there is a strong intuition that the phenomenaldomain is distinctive—if an experience appears to have a certainphenomenal property, then it has that property as phenomenalcharacter. The tenability of the form of disjunctivism that deniesthat veridical perceptions and hallucinations can have the samephenomenal character will depend on whether this epistemic assumptioncan plausibly be denied (see the discussion of this point in section3.4), and whether the disjunctivist can make a satisfactory case forthinking that veridical perceptions appear to have a phenomenalcharacter that hallucinations could not possess (see section 3.3).

4.2 The Causal Argument Against Disjunctivism

An influential argument against disjunctivism is the causalargument, first proposed by Howard Robinson (see Robinson 1985 and1994). The simplest version of the argument appeals to the followingtwo claims: (i) It is theoretically possible, by activating some brainprocesses involved when a subject genuinely perceives the world, tocause a hallucination subjectively indistinguishible from thatperception—a ‘causally matching’ hallucination.(ii) It is necessary to give the same account of the experiencesinvolved in genuine perception and hallucination when they have thesame neural causes. So we should accept that the kind ofexperience that occurs when a subject perceives the world is one thesubject could be having if she were hallucinating.

The general principle behind this second claim is ‘sameproximate cause, same immediate effect’. It is likely that thedisjunctivist will simply reject this principle. The disjunctivist mayinsist that in a case of genuine perception, even if the objects ofperception are distal causes of the subject’s experience, theyare also figure non-causally as essential constituents of it. So theoccurrence of the relevant brain processes won’t be sufficient toproduce the kind of mental event involved in perception, unless furthernon-causal conditions necessary for the occurrence of that kind ofmental effect also obtain. At this point, the disjunctivist and heropponent may simply disagree as to whether there are any psychologicaleffects that have significant non-causal constitutive conditionsattached. And this connects with familiar debates as to the tenabilityof externalist views in the philosophy of mind. (For further discussionof the causal argument see Langsam 1997, Snowdon 2005b, and Martin2004).

4.3 Neither Conjunctivism Nor Disjunctivism

There is another version of the causal argument that can be used toput pressure on the disjunctivist to accept that there is a commonelement to veridical perception and causally matching hallucination.(See Johnston 2004 and Martin 2004.) The proponent of this argument mayallow for the possibility that there are non-causal constitutiveconditions necessary for the occurrence of certain kinds of mentalevents, where such constitutive conditions may include the presence inthe environment of appropriate candidate objects of perception.So this version of the causal argument can accommodate thedisjunctivist’s claim that there are significant non-causalconditions necessary for the occurrence of the kind of experience thatoccurs when one veridically perceives the world. What this version ofthe causal argument relies upon is, rather, the claim that there are nosuch significant non-causal conditions necessary for the occurrence ofthe kind experience that occurs when onehallucinates. Theproponent of this modified causal argument claims that there are nonon-causal conditions necessary for the occurrence of the kind ofexperience that occurs when one hallucinates that cannot also obtainwhen one veridically perceives the world. So whatever kind ofexperience occurs when you have a causally matching hallucination of anF will also be produced when you have a veridical perceptionof anF. So there is, after all, a common element toveridical perception and causally matching hallucination.

Can the disjunctivist respond by saying that there is a non-causalconstitutive condition necessary for the kind experience that occurswhen one hallucinates—namely theabsence of anappropriate candidate object of perception in the subject’senvironment? A problem with this response is that it relies oncharacterising the kind of psychological effect involved inhallucination in terms of what it is not, namely a veridicalperception, and it is plausible to demand that it should be possible toprovide somepositive account of the kind of psychologicaleffect involved when one hallucinates.

This version of the causal argument does not rely on the generalprinciple ‘same proximate cause, same immediate effect’,so a proponent of the argument may allow that there is a kind ofmental event that occurs when one perceives the world whichdoesn’t occur when one hallucinates. Moreover, a proponent ofthe argument may also allow that there is an explanatory role to beplayed by the kind of mental event that only occurs when one perceivesthe world, which cannot be performed by appealing to the kind ofmental event that is common to perception and illusion, plus somefurther non-mental conditions. (For this idea see Peacocke 1993 andWilliamson 2000). However, the argument does put pressure on thedisjunctivist to accept that there is a certain kind of mental eventcommon to perception and hallucination—one that we should beable to give a positive, non-disjunctive account of. (See Burge 2005,2010 and 2011 for arguments to the effect that a denial of this claimis empirically untenable and incompatible with the methodology ofvision science.) It suggests that if one simply wants to claim thatgenuine perceptions are mental events of a kind that cannot occur whenone hallucinates, one should not be concerned to argue for adisjunctive account of perceptual experience. One’s concernshould simply be to oppose a conjunctive account of genuineperception. (For this line of criticism see Williamson 2000 andJohnston 2004).

One may be able to accept that a veridical perception and ahallucination differ mentally, while also accepting that they have acommon mental core. Mark Johnston offers an account of hallucinationalong these lines. He proposes that there is a respect in which theobjects of hallucination and the objects of seeing are akin. Accordingto Johnston, the objects of a subject’s hallucination arecomplexes of sensible qualities and relations that are not instantiatedin the scene before him, whereas the objects of veridical perceptionare spatio-temporal particulars instantiating such complexes. On thisview, there is, then, a common mental core to veridical perception andhallucination. In both cases one is aware of a ‘sensibleprofile’—a complex of qualities and relations.

The disjunctivist is generally willing to concede that perceptionsand subjectively indistinguishible hallucinations havesomething in common. So why should they not accept that whatis common to perception and hallucination is the occurrence of acertain kind of mental event whose nature is one that we can give apositive, non-disjunctive account of?

Martin argues that the naïve realist disjunctivist shoulddeny that it is possible to give a positive, non-derivative account ofthe kind of phenomenal event that occurs when one hallucinates. (Thisis to oppose the suggestion made in Dancy 1995. See Martin 1997, 2004and 2006. For discussion see Nudds 2009.). For if the naïverealist does offer a positive, non-derivative account of the kindphenomenal event that occurs when one hallucinates, and she alsoaccepts that this kind of event also occurs when one perceives theworld, then she will be under pressure to explain why the occurrence ofthis kind of event doesn’t screen off the explanatory role that sheassigns to her naïve realist account of the phenomenal characterof genuine perception. (For critical discussion of this objection, seeHellie 2013). Martin’s response to the argument is to say that thenaïve realist should affirm that in the case of a causallymatching hallucination, there is no more to the phenomenal characterof such an experience than that of being introspectivelyindiscriminible from a certain genuine perception. In the case of thecausally matching hallucination its subjective character is exhaustedby its possession of the negative epistemic property—that ofbeing introspectively indiscriminible from a veridical perception.

It might now be objected that this disjunctivist response stillintroduces a common element to veridical perception and causallymatching hallucination that screens off the explanatory role that thenaïve realist assigns to her distinctive account of thephenomenal character of veridical perception. Both a veridicalperception of anF and a causally matching hallucinationpossess the negative epistemic property of being introspectivelyindiscriminible from a veridical perception of anF. So whydoesn’t this screen off any explanatory role that the naïverealist might assign to the phenomenal properties that she claims onlya veridical perception can possess? Martin’s response is tosuggest that the property of being indiscriminible from anFhas an explanatory potential which is dependent on the explanatorypotential ofbeing anF. So the property ofactually being a veridical perception, and having the phenomenalproperties that only a veridical perception can possess, can still beregarded as having a crucial explanatory role to play.

However, this response still leaves the naïve realist in theposition of having to deny that it is possible to provide a positiveaccount of the phenomenal character of a causally matchinghallucination. Many have argued that this claim is ultimatelyuntenable. So the modified causal argument can be seen as part of anattempt to force the naïve realist disjunctivist into an untenableposition with respect to causally matching hallucinations.

5. Disjunctivist Accounts of Hallucination and Illusion

This section is concerned with what disjunctivists say about thefollowing: the nature of the kind of mental event that occurs when onehallucinates, the nature of the kind of mental event that occurs whenhas a perceptual illusion, and what the differences between such eventsmight be.

5.1 Hallucination

Some disjunctivists say relatively little about the nature ofhallucination (e.g., McDowell, Campbell and Brewer). For example,McDowell characterises hallucinatory experience as a “mereappearance” that such and such is the case, which seems to leaveopen whether a more positive account can potentially be given. Dancy(1995) suggests that the disjunctivist should offer a more directcharacterization of the kind of experience that occurs when onehallucinates, rather than simply characterising it solely by sayingthat it is like what it is not. He suggests that in a fully explicitversion of the disjunctive theory hallucination would be characterisedin a direct, positive way.

The disjunctivist who allows that veridical perceptions andhallucinations can have the same phenomenal character may take up thissuggestion. (See Logue 2012a and 2013.) This disjunctivist may be ableto provide some positive account of the phenomenal character thatveridical perception and hallucination can share, while allowing thatthere are certain mental properties distinctive of veridicalperception (e.g., its possessing an object-dependent intentionalcontent.) However, for reasons explained in the previous section,Martin argues that the disjunctivist who is a naïve realist aboutthe phenomenal character of veridical perception (and so who holdsthat veridical perceptions have phenomenal properties thathallucinations cannot possess) should reject Dancy’sproposal. Martin commits to the claim that in the case of certainhallucinations (i.e., those which have the same kind of proximatecause as veridical perceptions), there is no more to their phenomenalcharacter than that of being introspectively indiscriminible from averidical perception.

This particular claim has drawn a great deal of criticism. Siegel(2004) argues that Martin’s account fails to accommodate thedifferent kinds of hallucinations that can be experienced by a creaturewho lacks the conceptual capacities to make introspective judgementsabout its experience. E.g., suppose a dog is having a hallucination. Dueto conceptual incapacities the dog is not in position to know that heis not perceiving a tomato, so for the dog this experience isintrospectively indiscriminible from a perception of a tomato. However,from this fact alone it does not follow that the dog is having ahallucination of a tomato.

Siegel (2004) also argues that Martin’s account fails to capture thefact that our hallucinations are phenomenally conscious, for a statethat is not phenomenally conscious can satisfy the description ofbeing introspectively indiscriminible from a genuineperception. Furthermore, she argues (in Siegel 2008) that Martin’saccount cannot adequately explain certain effects ofhallucinations—i.e., what grounds one’s positive knowledge ofthe kind of experience one is and isn’t having. Along related lines,Sturgeon (1998) suggests that the disjunctivist who denies that it ispossible to provide a positive account of the phenomenal character ofa hallucination does not have the resources to explain adequately howit is that having a hallucination of anF can provide onewith positive knowledge concerning what it is like to veridicallyperceive anF. (See also Pautz 2010 and 2011.) Johnston(2004) argues that the disjunctivist offers no satisfactoryexplanation of the fact that hallucination can provide us withoriginal de re knowledge of quality (e.g., the fact that ahallucination as of a red object can provide its subject with de reknowledge of the quality of redness).

Martin (2006) attempts to defend his account of hallucinationagainst his critics, by (a) focusing on the issue of how we shouldunderstand the notion of indiscriminability in play in his talk of‘introspective indiscriminability’, and (b) focusing on thequestion of the model of introspection we should adopt when our concernis with the way in which we introspect our phenomenally consciousmental states. Both aspects of Martin’s defence of his view havebeen contested.

Martin suggests that the notion of indiscriminability that thedisjunctivist should appeal to is an ‘impersonal’,‘objective’ one. He compares the way in which we can talkof objects being visible or invisible. He suggests that in certaincontexts, when we say that something is invisible, we may not betalking about the way a given individual, or group of individuals, issuch that they cannot succeed in seeing the object. We may rather betalking about whatvision can and cannot discern. Furthermore,in asking what vision can reveal to us, we can ask in terms of howvision actually is, or ways in which visioncould be. The mostextreme claim of invisibility would be concerned with the latternotion. The suggestion seems to be that we should not think that such‘impersonal’, ‘objective’ talk of invisibilityneed be reducible to claims about what a given subject, group ofsubjects, or ideal subject would or would not see. So similarly, weshould not take the impersonal, objective talk of introspectiveindiscriminability as reducible to claims about what a given subject,group of subjects, or ideal subject would or would not come to knowthrough introspection.

Martin notes an objection that this comparison with sight might giverise to. When two objects are impersonally indiscriminible throughsight, we tend to think that the objects in question must share aproperty—an appearance—that is detectible throughvision. The fact that two visible objects cannot be told apart by sightsuggests that there is something in common between them that sight doesdetect. So we might also think that if two experiences areintrospectively indiscriminible, these experiences must share aproperty—a phenomenal property—that introspection istracking. Martin’s response to this objection is to reject amodel of introspection that he thinks lies behind it. Martin suggeststhat in a case in which two objects are impersonally visuallyindiscriminible, we are led to posit a common appearance the objectsshare that vision can discern, because we think of sight as a mode ofcoming to be aware of a realm independent of it. So, according toMartin, the same story will apply to the case of introspection only ifwe suppose that when one introspects the phenomenal character ofone’s experience one is detecting features of some realm that isindependent of one’s introspective access to it. Martin arguesthat if one adopts this model of introspection then one will eitherhave to allow that it is possible for one’s experience to have areal phenomenal nature rather different from the one it introspectivelyseems to have, which remains inaccessible to introspection, or one willhave to accept that introspection involves the use of a“super-mechanism”, which tracks the phenomenal character ofone’s experience in a such a way that it cannot fail, or can onlyfail when it is knowable that it has.

On Martin’s recommended alternative, a subject’s introspective perspective on herexperiencecoincides with, and is not independent of, herexperiential perspective on the world. There is no way of specifying amechanism of introspection such that there could be a way in which itgoes wrong, not because the faculty of introspection is a“super-mechanism”, but rather because there is no mechanismof introspection.

According to Martin, if we think of introspective awareness ofexperience in the wrong way, the negative epistemic condition (that ofbeing introspectively indiscriminible from a veridical perception) isread only as a condition on one’s cognitive awareness, and notas a condition on experience itself. And Martin thinks that this liesbehind many of the objections to his account. In response, Martintries to argue that read in the right way introspectiveindiscriminability guarantees that phenomenal consciousness ispresent. For according to Martin, the disjunctivist should stress theconnection between phenomenal consciousness and having a point ofview, or perspective on the world, a connection central toNagel’s (1974) discussion of consciousness. So the negativeepistemological condition when correctly interpreted will specify notjust a subject’s cognitive response to their circumstances, butrather their perspective on the world (which the introspectiveperspective coincides with), and this will be sufficient for there tobe something it is like for them to be so. It is worth noting that thereasons that Martin gives for recommending this account ofhallucination appear to apply just in the case of a causally matchinghallucination (i.e. a hallucination that is subjectivelyindistinguishable from a veridical perception and which involves thesame kind of proximate cause and brain state as that involved in thecorresponding veridical perception). Moreover, it is not obvious thata disjunctivist needs to give the same account of allhallucinations. So if a disjunctivist were to agree to Martin’sreasoning about causally matching hallucinations, it may be open toher to provide a positive account of other hallucinations.

Fish (2008 and 2009) proposes a rather different disjunctivist accountof hallucination, which applies to all hallucinations, includingcausally matching hallucinations. Fish offers what he calls a minimal,butpositive, story about hallucination. According to Fish, amental state that may be intrinsically quite different from a veridicalperception might come to be mistaken for a veridical perception andtherein acquire the status of hallucination. Fish thinks thatthe demand for a more substantial intrinsic characterisation ofhallucination is misguided, but that the following positive story canbe told. The indistinguishability of hallucination from veridicalperception is grounded in the similarity of their effects. Ahallucination of anx is a mental state that, whilst notbeing a veridical perception of anx, nevertheless comes tohave effects that are sufficiently similar to those a veridicalperception would have had. If the subject is conceptuallysophisticated these effects will include higher-order beliefs aboutseeing anx, or seeming to see anx. If the subjectis not sophisticated enough to have such beliefs at all, the effectswill be solely behavioural.

This account allows that hallucinations may have no phenomenalcharacter, and even in those cases in which the mental state does havephenomenal character, the phenomenal character it has may well notaccount for the particular content of the hallucination. (For thesuggestion that the disjunctivist should accept this consequence, seeSturgeon 2006 and 2008. For criticism of Fish’s account, seeSiegel 2008).

5.2 Illusion

Different disjunctivists group together perceptions, illusions andhallucinations in different ways when offering their disjunctivecharacterisations of perceptual experience. At points it looks asthough Hinton is suggesting that illusions can be grouped togetherwith veridical perceptions. For in certain places he says that hisPerception-Illusion disjunctions permit a description of what is seenin terms of how the thing looks, thereby allowing the following kindof Perception-Illusion disjunction: ‘S sees somethingwhichlooks blue or is having that illusion’ (1973,61). In other places he says things that suggest that the illusion ofan object appearing blue should not be grouped together with veridicalperception, for he says that an experience as of blue is equivalent tothe mere disjunction ‘Either I actually see an optical objectthat is blue in colour, or I am in some situation… that is tome like that one’ (1967b, 12). Snowdon groups togetherperceptions and illusions in his disjunctive characterisation ofexperience: ‘Either (there is something which looks toS to beF) or (it is toS as if there issomething which looks toS to beF)’. Incontrast, McDowell, in his appeal to the idea offacts beingmade perceptually manifest, appears to group together illusions andhallucinations: an appearance that such-and-such is the case can be‘either a mere appearance or the fact that such-and-such is thecase making itself perceptually manifest to someone’.

The differences in the ways these philosophers formulate theirparticular disjunctive characterisations may in part reflect theirdifferent particular interests in appealing to a disjunctive account ofexperience. For example, Snowdon’s primary concern is to block anargument about what is required for the perception ofobjects(see section 6.1), whereas McDowell is concerned to defend an accountof experience that safeguards the distinctive epistemological role ofgenuine perception in providing us withpropositionalknowledge. It is not clear that McDowell needs to deny that there are anumber of facts made perceptually manifest to you when you suffer anillusion, in which case he might allow that it is possible to grouptogether veridical perceptions and illusions as cases in which certainfacts are made manifest to their subject.

Similar considerations may apply in the case of experiences that wemight describe aspartial hallucinations—cases inwhich a subject hallucinates an object while veridically perceivingother aspects of her environment. For example a subject mightveridically perceive a table in front of her while hallucinating a pinkrat on top of it. One question that can be asked of McDowell’sdisjunctivism is whether, according to it, we should treat such casesas ones in which the fact that there is a table in front of the subjectis made perceptually manifest to her, despite the fact that she ishallucinating a pink rat.

Martin (2004) offers a sketch of how a naïve realist mightdevelop an account of partial hallucination. He suggests that ratherthan focusing on experiencesper se, we can focus onthe variousaspects of an experience—“thedifferent entities that one can experience and the ways in which theycan appear to one” (2004, 81). We can then explain those aspectsof a partial hallucination that are not genuinely perceptual in termsof “that aspect of experience’s indiscriminability from thecorresponding aspect of a perceptual awareness of that element”(2004, 81). Martin also appeals to this idea in offering a suggestionas to what the disjunctivist should say about the experience ofimpossible scenes. His suggestion is that the disjunctivist shouldexplain such experiences not by direct appeal to the idea of veridicalperception of the impossible scene, but rather by explaining how anexperience with each of the constituent elements is indiscriminable inthat respect from a perception of that element. (For criticism of thisproposal see Siegel 2004). One concern with this proposal is whetherthere may be some problem for the disjunctivist in thinking of suchexperiences as having a sort of hybrid nature, given that thedisjunctivists think that perceptions and hallucinations are mentalevents with such different natures. (For an argument for the claim thataccommodating certain illusions poses significant difficulties for thedisjunctivist, see Smith 2010. See also Millar 2015).

A further question to be asked in this context is whether thedisjunctivist should treat all cases of illusion as equivalent tocases of partial hallucination. For example, if a subject perceives agreen object that looks to her to be blue, should the disjunctivistsay that the subject is perceiving the object but hallucinating theblueness it seems to possess? Brewer (2008) offers a disjunctivistaccount of certain illusions that he thinks need not be treated ascases of partial hallucination (e.g., the Mueller-Lyerillusion). According to Brewer, such illusions are simply cases inwhich the direct object of experience has visually relevantsimilarities with paradigms of a kind of which it is not in fact aninstance. The fact that the direct object of perceptionlooksF, but isn’t, is explained in terms of the ideathat the object may intelligibly be taken to beF, when seenfrom the point of view in question, in the relevant circumstances ofperception, in virtue of its relevant similarities with certainparadigmFs. In the case of certain illusions, when an objectlooks to be a certain way that it isn’t, a disjunctivist mightplace emphasis on the idea that this misleading appearance is publiclyobservable; for instance, it might be the sort of thing one is able tophotograph. The disjunctivist might then say that in such cases we canascribe to the seen object a publicly observable feature—a‘look’ or ‘appearance property’ that theobject has. When one sees the object one may be visually aware of thisappearance property—its having the look of anF. Andone’s awareness of this appearance property may intelligiblymislead one into mistakenly judging the object to beF. (Forrelated proposals about perceptual illusions, but which differ fromBrewer’s account in important respects, see Antony 2011 andGenone 2014. For defence of the claim that empirically grounded modelsof illusion may be congenial to naïve realism, see Phillips2016.)

6. Disjunctivism and the Causal Theory of Perception

Some philosophers associated with the disjunctive theory of perceptionare simply concerned to argue that certain common element claims lackadequate justification, thereby leaving us free to resist argumentsabout perception that depend upon such claims in their premises. Forexample, Paul Snowdon, one of the philosophers most associated withdisjunctivism, appeals to the possibility of a disjunctive approach toperceptual experience in order to undermine an argument for a thesisabout our concept of perception. According to the thesis that Snowdonaims to challenge it is a conceptual requirement that, necessarily, ifS (a subject) seesO (an object) thenO iscausally responsible for an experience undergone by (or had by)S. This thesis has been labelled the Causal Theory ofPerception (henceforth it will be referred to as the CTP).

H.P. Grice (1961) originally propounded the main argument for theCTP. (Other advocates of the theory include Pears (1976) and Strawson(1974)). Grice’s argument takes the following general form. Weare asked to consider cases in which a subject is having an experienceappropriate for seeing an object of a certain kind—e.g., thesubject is having an experience such that it seems to her as if thereis a clock in front of her. There is in fact a clock in front of thesubject, however, the subject fails to see the clock, for thesubject’s experience is a hallucination—perhaps inducedby a neuroscientist stimulating her visual cortex. It is argued thatsuch cases are indeed conceivable, and that in such cases the bestexplanation of the subject’s failure to see the object before heris the absence of an appropriate causal connection between the objectand her experience. Hence the CTP is justified.

According to Snowdon (1980, 1990, 1998, 2011), the plausibility ofthis argument rests on a conception of perceptual experience that iswedded to a common element assumption—in particular, theassumption that the kind of experience one has when one genuinelyperceives the world is one whose intrinsic nature is independent ofthe kinds of objects perceived. On this conception of experience,experiences are amongst the events, the intrinsic natures of which areindependent of anything outside the subject. According to this view,the ‘looks’ sentences that are true in cases ofhallucination and in genuine perception are made true by (or are truein virtue of) exactly the same kind of occurrence in both cases. Oncethis conception of perceptual experience is in play, we might then askafter the extra-mental conditions required for seeing objects in ourenvironment. The Gricean thought experiments suggest that simplyhaving an experience that matches your surrounding environment willnot, in itself, be sufficient for seeing objects in yourenvironment. So the temptation then is to think that an appropriatecausal connection between your experience and those objects isnecessary for you to see them. The motivation for the CTP is thereforeundermined, according to Snowdon, unless it can be shown that it ispart of our concept of perception that the common element claimassumed in the argument is correct.

Following Hinton’s lead, Snowdon argues that from the factthat ‘looks’ sentences are true in cases of hallucination and inveridical perception, and are not ambiguous, it does not follow thatthey are made true by (or are true in virtue of) exactly the same kindof occurrence in both cases, for they may instead have disjunctivefulfilment conditions. According to the disjunctive theory Snowdonconsiders, the claim that ‘It looks toS as of there is anF’ should be treated as being true in virtue of twodistinct sorts of states of affairs:Either (there issomething which looks toS to beF)or (itis toS as if there is something which looks toS tobeF). This disjunctive theory allows that the two cases(perception and hallucination), which are described in the same way,might be of a quite different nature. In particular, it allows that thekind of experience a subject has when she genuinely perceives theworld is such that its intrinsic nature is not independent of thekinds of objects perceived. For Snowdon, the availability of thisdisjunctive approach to perceptual experience undermines the argumentfor the CTP, unless proponents of the argument can say something whichis legitimately conceptual and which shows that this disjunctiveapproach must be wrong. (So note that according to Snowdon, anassertion of the disjunctive theory is not actually needed for arejection of the Gricean argument for the CTP.)

For defence of the causalist approach against disjunctivism, see Lowe2008. For a defence of the claim that disjunctivism is compatible withthe CTP, see Child 1992, 1994 and 2011.

7. Conclusion

As we have seen, there are a variety of different disjunctivist views,often motivated by quite different concerns, and the disagreementsthat these disjunctivists have with their opponents are relevant to anumber of debates in the philosophy of perception andepistemology—debates about the metaphysics and phenomenology ofperceptual experience, our concept of perception, the epistemologicalrole of perceptual experience, and self-knowledge. Many of thedisjunctivist views and arguments that have been outlined here havebeen proposed relatively recently, and the debates they have inspiredseem set to continue. In a further recent development disjunctivetheories of perception have inspired similar disjunctive approaches inthe philosophy of action—concerning both the ontology of actionand a subject’s reasons for performing actions. (For discussion ofdisjunctive approaches to action see Haddock and McPherson 2008b,Ruben 2008, Hornsby 2008 and Dancy 2008.)

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The author would like to thank David Chalmers for his commentson earlier drafts, which helped to improve the present entry.