When you see a ripe lemon in a supermarket, it seems eminentlyreasonable for you to believe that a lemon is there. Here you have aperceptual experience since you consciously see somethingyellow. And your experience seems tojustify your beliefsince your experience seems to make it reasonable for you to believethat a lemon is there.

Our perceptual experiences of the world outside us seem to justify ourbeliefs about how the world outside us is. If that’s right, aquestion in the epistemology of perception remains open: how do ourexperiences justify beliefs about the external world? And a questionin the philosophy of mind remains open as well: what are ourexperiences themselves like?

This entry will survey interactions between the epistemology ofperception and the philosophy of mind. Following the existingliterature, the focus will be on visual perceptual experience. Thereader is invited to consider how generalizations to other sensesmight or might not succeed.

Section 1 considers theories of experience and what implications theymight have for the epistemology of perception. Section 2 considersperceptual phenomena, such as attending or dreaming, with specialimplications for the epistemology of perception.

• 1. Theories of Experience
  • 1.1 Sense-datum Theories
  • 1.2 Raw Feel Theories
  • 1.3 Perceptual Content
  • 1.4 Consciousness
  • 1.5 Degreed Perception
• 2. Perceptual Phenomena
  • 2.1. Perceptual Error
  • 2.2 Successful Perception
  • 2.3 Attention
  • 2.4 Cognitive Penetration
• Bibliography
• Academic Tools
• Other Internet Resources
• Related Entries

1. Theories of Experience

For our purposes, a theory of perceptual experience aims to identify afeature that isconstitutive of perceptual experience: it isshared by all perceptual experiences, and identifies at least part oftheir nature. In this section, we will consider various potentiallinks between theories of experience and the epistemology ofperception that can be captured with the following template:

Epistemology-Mind Link
If experiences justify beliefs about the external world, thenexperiences have property \(P\).

The idea here is that experiences have to be a certain way in order tojustify beliefs. Now, philosophers might accept a particular instanceof the E-M Link, but disagree about whether experiences are the waythey need to be in order to justify beliefs about the external world.For example, Davidson (1986) and McDowell (1994) agree thatexperiences justify beliefs about the external world only ifexperiences have contents that can be assessed for truth. Davidson(1986) argues that experiences do not justify beliefs about theexternal world on the grounds that they lack truth-assessablecontents, whereas McDowell (1994) argues that experiences must havetruth-assessable contents given that they justify beliefs about theexternal world (more on their dispute insubsection 1.2).

We can organize our discussion of such agreements and disagreementsaround the following trio of claims:

Epistemology
Our experiences justify beliefs about the external world.

Epistemology-Mind Link
If our experiences justify beliefs about the external world, then ourexperiences have property \(P\).

Mind
Our experiences do not have property \(P\).

If Epistemology and Epistemology-Mind Link are true, then Mind isfalse. Something will have to go. Approaches will vary according totheir verdict on what exactly must go.

In what follows we survey the most prominent instances of the trio. Wewill start with sense-data theories, then turn to raw feel theories,and theories on which experiences have propositional contents. We willclose the part by considering the conscious character ofexperiences.

Our survey of theories of experiences will not be exhaustive, but Iwill briefly discuss an approach that complicates my framing of thedebates in terms of “visual experiences”. Some have arguedthat, when the ordinary shopper observes the lemon in the supermarket,her visual mental life is not as simple as it seems. In particular,rather than having a unitary visual experience, perhaps she has avisual sensation and a visual seeming (Lyons 2005; Tucker 2010;Brogaard 2013; Reiland 2015; also Bengson 2015 as a fellow traveler).Call this the “hybrid” picture of experience.

To get a feel for the hybrid picture, consider a contrast between anexpert bird-watcher and an ordinary perceiver, both observing anorthern bobwhite. The hybrid theorist would say that they have thesame rudimentary visual sensation in some way involving colors andshapes, with only the expert has a visual seeming specifically to theeffect that a northern bobwhite is present. Here the visual sensationshared by the expert and novice is sensory in character, but theseeming had only by the expert is itself not sensory. (For furtherexamples, see the opening of Tucker 2010).

The seeming might even be sharable in principle with subjects who lackvisual consciousness altogether (Tucker 2010, also Lyons 2005 withdifferent terminology, Brogaard 2013 however disagrees that visualseemings can be detached so far from visual sensation). That seemingsare not sensory does not obviously entail that they are perceptuallyamodal entirely, Lyons for instance seems to tie down his“nonexperiential looks” to different perceptual modalitiessuch as vision or audition.

The example of the novice vs. the expert is suggestive, but what wehave said so far leaves open the respective natures of sensations andseemings, as well as of how visual experiences are to be understood inrelation to them. Given all of this indeterminacy, as well as the roomfor debate about whether we even have good reason to complicate thestructure of visual experience in this way (see Chudnoff andDidomenico 2015 for criticisms), the discussion below will be framedsimply in terms of visual experiences. That said, the discussionshould remain applicable to experiences understood as combinations ofsome sort of sensations and seemings. The discussion should also inprinciple be adaptable to apply individually to sensations only or toseemings only, depending on the reader’s preferred category. Atsome key stages we will explicitly highlight where the distinctionmight be especially useful to apply and explore.

1.1 Sense-datum Theories

On sense-datum theories, whenever you have a visual experience as ifthere is something present that is red, there really is somethingpresent that is red—a sense-datum. Now, in many cases ofillusions and hallucination, there won’t be any ordinary redthing around for you to experience even if there seems to you to be ared thing present. So sense-data are either going to be mental objectsor strange non-mental objects. Sense-datum theories usually departfrom the following principle:

The Phenomenal Principle
Whenever you visually experience it to be that case that something is\(F\), then there is something \(F\)that you experience (Robinson 1994).

Let’s first examine an epistemological case for sense-datumtheories. Here the direction of flow is from epistemology to thephilosophy of mind. We can find it in the following famous quote fromH.H. Price:

When I see a tomato there is much that I can doubt … One thinghowever I cannot doubt: that there exists a red patch of a round andsomewhat bulgy shape, standing out from a background of othercolour-patches, and having a certain visual depth, and that this wholefield of colour is presented to my consciousness … (Price 1932:3).

On Price’s line of thought, perceptual experiences do afford uswith some certainty. When Price sees a tomato, he may be certain thatthere is something red and round present. According to critics of theargument, Price is not entitled to be certain of any such thing. Forexample, his experience might merely represent that there existssomething red and round present, where such representation can occureven if nothing red and round is present (for more on this objectionsee the entry onthe problem of perception (section 3.1.2).

Let’s now turn to the status of beliefs about ordinary objectsin the external world, and the flow from the philosophy of mind toepistemology. We can organize our discussion under the followinginstance of the trio:

Epistemology
Experiences justify beliefs about the external world.

Epistemology-Mind Link 1
If experiences justify beliefs about the external world, thenexperiences are not relations to sense-data.

Mind 1
Experiences are relations to sense-data.

In principle, a sense-datum theorist might accept E-M Link 1 and Mind1, and conclude that Epistemology is false. For example, she mighttake up a coherence theory of justification, on which our beliefsabout the external world are justified by their coherence with eachother and not by experiences (see the entry onsense-data (section 3.2).

In the usual line of discussion, philosophers affirm Epistemology andE-M Link 1, and conclude that Mind 1 is false (see Berkeley 1710/2008:sect 18 or Reid 1764/1997: ch. 1). Sense-datum theories tell us thatthe things we are directly aware of in perceptual experience are notordinary external objects. As the common metaphor has it, sense-datatheories draw aveil of ideas over the world. The usualobjection holds that this veil makes it impossible for us to gainknowledge or justified belief from experience about the externalworld. Philosophers such as Berkeley and Reid reject sense-datumtheories on the grounds that we do have epistemic access to theworld.

In response, the sense-datum theorist might deny E-M Link 1. Inparticular, the theorist might say that experiences justify beliefsabout the external world when complemented with reflection on how theyare best explained (Russell 1912). Call this the IBE approach since itconcerns Inferences to the Best Explanation of our experiences (seeVogel 1990 for more contemporary discussion). Setting aside debateabout how such an explanation might go, and why it might be the best,the response might not go far enough.

To see why the IBE approach might not go far enough, consider the ideathat experiences providenon-inferential justification forbeliefs about the external world. If experiences providenon-inferential justification for beliefs about the external world,they justify beliefs through a route that does not involve furtherbeliefs. Compare how your sharp pain might justify you directly inbelieving that you are in pain, without further beliefs playing anyrole. Contrast how your thermometer might justify you in believing youhave a fever only in conjunction with your having reason to believethe thermometer works. Non-inferential justification is justificationthat does not involve auxiliary beliefs (see Pryor 2005 for moredetail).

On the IBE approach, it seems that experiences at best give usinferential justification for beliefs about the external world.That’s because they justify us only in conjunction with whateverbeliefs their best explanation brings in. Experiences arguably dobetter (Johnston 2006). The veil of ideas objection might then bebetter put as follows:

Epistemology1
Experiences give non-inferential justification for beliefs about theexternal world.

Epistemology-Mind Link 2
If experiences give non-inferential justification for beliefs aboutthe external world, then experiences are not relations tosense-data.

So,

not-Mind 1
Experiences are not relations to sense-data.

Even still, it is unclear why sense-datum theories should rule outgetting non-inferential justification from experiences. Perhaps if asense-datum theory is true, we at best see external objectsindirectly, by means of seeing sense-data. But this is only a pointabout seeing. Our justification for beliefs could still benon-inferential (Moore 1953; Silins 2011). The crucial question fornon-inferential justification is about the role of background beliefs,and the mental process of indirect perception need not make use ofbackground beliefs. For instance, whether you indirectly perceiveobjects by means of sense-data might instead just be a matter of howthe sense-data are caused, leaving open the possibility that you gainnon-inferential justification for beliefs about the external worldfrom sense-data.

Let’s now zoom out to a big picture assessment of the epistemicimplications of sense-datum theories.

The thought driving the veil of ideas worry is that if experiencesfail to put us in direct contact with reality, then they cannotjustify beliefs about external reality. This thought is meant to getus to the conclusion that sense datum theory is false. But it might gotoo far.

The first ramification concerns seeing objects. According to manyviews, we see ordinary extended objects by seeing their surfaces,rather than seeing them directly (see Moore 1918 or Broad 1952, andClarke 1965 or Campbell 2004 for dispute). As far as seeing objectsgoes, their facing surfaces play the same role as sense-data did onmany versions of the sense-datum theory—intermediaries notidentical with objects that still permit us to see objects by seeingthem. But now, if we endorse the veil of ideas objection, there is arisk that the facing surfaces of objects will be a veil over the restof external reality. Call this theveil of surfaces. Ourexperiences might fail to give us access to whether we live in a worldof ever shifting facades or instead a world of three-dimensionalobjects as they are ordinarily conceived. Descartes arguably statesthis problem when he writes:

I remember that, when looking from a window and saying I see men whopass in the street, I really do not see them, but infer that what Isee is men, just as I say that I see wax. And yet what do I see fromthe window but hats and coats which may cover automatic machines? (PW,p. 21 )

If the veil of ideas objection succeeds against sense-data theories,it might also rule out the theory that we directly perceive onlysurfaces. It is not clear whether the objection can get us thatfar.

The veil of ideas objection also has controversial ramifications forcases of illusion or hallucination. When something looks red to youwhen it isn’t, or when you have a hallucination of a bloodydagger in front of you, your experience fails to put you in directcontact with reality as it is. According to many approaches, yourexperience might still—misleadingly—justify you inbelieving that reality is the way it visually appears to be. However,if the thought driving the veil of ideas objection is correct,experiences only justify in those cases when you are seeing things asthey are. This is quite a demanding view, one that rules outjustification in a wide range of cases where many think it is present.(For more discussion of views that exclude perceptual justificationfrom cases of illusion or hallucination,see section 2.2.).

1.2 Raw Feel Theories

According to sense-data theories, all visual experiences relate us toobjects with the properties attributed by our visual experiences. Atan opposite extreme, one might hold that experiences are “rawfeels”, failing to present the world to us in any way. To get afeel for this line of thought, consider the experience of“seeing stars”. According to some views, your experiencehere is a mere sensation, failing to present your surroundings to you(cf. Smith 2002: 130–1). On these views, the expression of“seeing stars” is extremely misleading here, as you do notliterally see stars, and do not even figuratively see anythingelse—it is not as if your experience is of anything in thescene. According to raw feel theory, all visual experiences are infact like this, not just exceptional ones. As Bonjour puts it, wecapture what our visual experiences are like “in terms ofpatches of color arranged in two-dimensional visual space”(2001: 32). (For a survey of views that could fall under the headingof “raw feel theory” as used here, see entry oncontents of perception (section 2.1).

In a passage from “A Coherence Theory of Truth andKnowledge”, Donald Davidson can be read as using raw feel theoryto argue for a skeptical epistemological conclusion:

The relation between a sensation and a belief cannot be logical, sincesensations are not beliefs or other propositional attitudes. What thenis the relation? The answer is, I think, obvious: the relation iscausal. Sensations cause some beliefs and in this sense are the basisor ground of those beliefs. But a causal explanation of a belief doesnot show how or why the belief is justified. (1986: 310)

By itself, the view that experiences are raw feels is silent aboutwhether experiences are able to justify beliefs about the externalworld. To get to conclusions about epistemology, some sort of linkingprinciple is needed. Davidson’s idea is that a source can supplyjustification only if it has propositional content, so that the sourceis assessable as accurate or inaccurate, depending on whether therelevant proposition is true. On this way of setting up the issues, anexperience has “propositional content” by having contentthat is assessable for truth (for further elaboration of the idea thatexperiences have propositional content, see the entry onthe contents of perception). Given Davidson’s demand, experiences would be unable to justifybeliefs if they were merely raw feels or sensations. (For importantprecedents to Davidson here, see Sellars 1956 and Popper 1959: chapter5. For further contemporary discussion, see Bonjour 1985; McDowell1994; Brewer 1999; and Pryor 2005.).

We can sketch the issues raised by Davidson with the followinginstance of our trio:

Epistemology
Experiences justify beliefs about the external world.

Epistemology-Mind Link 3
If experiences justify beliefs about the external world, thenexperiences have propositional content.

Mind 2
Experiences are raw feels without propositional content.

The Davidsonian response to the trio is to accept E-M Link 3 and Mind2, but to deny Epistemology.

A different response to the trio accepts E-M Link3, but usesEpistemology to reject Mind 2. This position was occupied by McDowell1994 and Brewer 1999 (although they later revised their views inBrewer 2006 and McDowell 2009).

Let us focus on debate about E-M Link 3, the common ground betweenDavidson, McDowell and Brewer. It can be resisted by raw feeltheorists, as well as by non-raw feel theorists who fall short ofattributing propositional contents to experiences.

Why believe E-M Link 3 at all? Davidson’s own case appeals tothe claim that, in order for an experience to justify a belief, theexperience must make more probable or entail the content of the belief(he also uses the further assumption that only propositional contentscan do any such thing). It’s not clear why all raw feeltheorists must accept the demand. Think back to the experience of“seeing stars”, and suppose that the experience is indeeda raw feel. The experience might still justify the belief that you arehaving that particular experience. Analogously, if pains are bestunderstood as raw feels, they arguably could still justify you inbelieving that you have them. Now, if experiences could lackpropositional contents and still justify you in believing you havethem, why couldn’t they still also justify beliefs about theexternal world? In particular, at least if background beliefs areallowed to play a role, it seems perfectly possible for beliefs aboutthe external world to be justified thanks to the availability ofinferences linking particular raw feels with particular conditions ofthe external world. The justificatory structure here would look likethis:

(For a contemporary view with this sort of structure, see Bonjour2001).

One also might try to meet the spirit of the demand that justifiersincrease probability or entail without attributing propositionalcontents to experiences. Here it’s important to note the richrange of ways in which experiences might be directed at the world.Many of these ways need not involve propositional content.

First, even if experiences lack contents that are assessable fortruth, experiences might still have contents that are assessable foraccuracy. Burge 2010 suggests that experiences have non-propositionalcontents of the form ‘that \(F\)’, and areaccurate just in case the referent has the property \(F\).Alternatively, consider how a map or picture mightbe accurate or inaccurate without being true or false. Whenexperiences are accurate in either of these ways, other contents ofbeliefs will be true. So experiences could lack propositionalcontents, but still count as close enough to entailing the contents ofbeliefs or to increasing the probability of the contents ofbeliefs.

Second, experiences might lack contents altogether, and not beassessable for truth or accuracy, but still be related in importantways to relations to the world such as seeing (Campbell 2002; McDowell2009; Brewer 2006, 2011). According to these approaches that resistthe ascription of content to experiences, your experience justifies abelief about the world only when your experience is a case of seeingthe world as it is. You can see the world as it is only if it is infact that way. Here many of your experiences might be supremelypositioned to justify whether or not they have any content. (For moreabout such approaches,see subsection 2.2.).

In sum, raw feel theorists might be in a good position to reject E-MLink 3. Moreover, even if experiences are not raw feels, they mightalso lack propositional contents, and still be directed at the worldin a way that helps them to justify beliefs.

1.3 Perceptual Content

Let us now turn to more fine-grained connections between contents ofexperience and perceptual justification, focusing on contents ofexperience that can be assessed for truth.

1.3.1 Necessity of Content

First, is having specifically the content that \(p\)necessary for an experience to justify believing that \(p\)?Here is a first pass at capturing the issue:

Epistemology-Mind Link4
If your visual experience \(e\) gives you justificationto believe some external world proposition that \(p\),then \(e\) has the content that \(p\).

A challenge comes from cases when you use an experience and backgroundbeliefs to extrapolate far beyond any content the experience mighthave. For example, when I have an experience in New York with thecontent that the traffic light is red, my background beliefs enablethe experience to justify me in believing that cars might still bepermitted to turn right. But this legally informed belief is in acontent that most likely does not figure in my experience.

To accommodate extrapolation beyond experience thanks to auxiliarybeliefs, the simplest response is to focus on non-inferentialjustification that does not involve auxiliary beliefs.

Epistemology-Mind Link5
If your visual experience \(e\) gives younon-inferential justification to believe some external worldproposition that \(p\), then \(e\) hasthe content that \(p\).

If Link5 is true, it allows for rich connections between theories ofperceptual experience and theories of perceptual justification.Consider for instance the debate about “high-level”content. Very roughly, this debate is about whether our experiencesmerely represent colors, shapes and locations, or whether theyrepresent thicker properties or relations such as causing anexplosion, being a fake Louis Vuitton bag, being virtuous, or beingglad to see you (for more see the entry onthe contents of perception). If Link5 is true, and we have non-inferential justification forbelief in high-level contents, it will follow that some of ourexperiences have high-level contents as well. But how to establishthat our experiences give us non-inferential justification for somehigh-level beliefs?

One route is to try to leverage the psychological immediacy of ourformation of some high-level beliefs. When the fashionista sees thedroopy bag marked “Louis Vuitton” in a cheap Shenzhenmall, she does not need to pull out her lighter to test whether thematerial melts likes plastic. Instead she forms her belief that thebag is a fake Louis Vuitton without any conscious reflection.Likewise, we don’t need to puzzle out whether our loved ones arepresent when we see them—we seem to recognize them on the basisof our experiences without reasoning. Still, it may be that auxiliarybeliefs are playing a role in all these examples while remainingunconscious. The psychological immediacy of belief formationneedn’t go along with non-inferential justification (seeMcDowell 1982).

For further discussion of how to show we have non-inferentialjustification from experiences for some beliefs in high-levelcontents, and of whether the experiences themselves would need to havehigh-level contents to do so, see Millar 2000, McDowell 2009, orSilins 2013.

For further defense of the claim that an experience justifies a beliefonly if it has a content identical with that of the belief, seeMcDowell 1994 and Brewer 1999. For critical responses, see Speaks 2005and Byrne 2005.

1.3.2 Sufficiency of Content

Is having the content that \(p\) enough for anexperience to justifying you believing that \(p\)? Hereis a first pass at capturing the idea:

Sufficiency First Pass
If you have an experience \(e\) with the content that\(p\), then \(e\) gives youjustification to believe that \(p\).

The Sufficiency thesis is not formulated in terms of non-inferentialjustification. For all it says, whenever an experience justifies abelief, it does so only in a way involving the assistance of anauxiliary belief. Still, the picture does mesh well with views onwhich experiences give non-inferential justification, and we mayunderstand it in those terms in what follows.

Our thesis does need to be qualified. For example, suppose that yougain convincing evidence that you are the victim of an illusion, aswhen you learn that the lines of the Müller-Lyer illusion are thesame in length even though they look to be different in length:

Figure 1. Müller-Lyer illusion^[1]

Your experience does not give you justification to believe that thelines are different in length once you have gain the evidence they arethe same in length. Such cases are ones of “defeat”, wherefurther evidence opposes or otherwise disrupts your receipt ofjustification from your experience (some cases may be like someonewriting over the graffiti drawn by experience, other cases may be likesomeone erasing the graffiti drawn by experience, and perhaps thereare further variants of defeat as well). To take account of suchcases, the fan of Sufficiency can say that

Sufficiency
If you have an experience \(e\) with the content that\(p\), then \(e\) gives you defeasiblejustification to believe that \(p\).

Here the core idea is that your experience gives you justificationunless you have gained evidence that your experience ismisleading.

For defenses of theses along the lines of Sufficiency, see Pollock(1974), Pryor (2000) or Huemer (2001, 2007). Their strategies put muchweight on what it is like to have an experience (see more insection 2.4 on this sort of strategy). A different approach tries to exploit theway that experiences come to have their contents, for example byarguing that experiences are likely to have true or accurate contentsgiven the way they come to have their contents. For examples of thisstrategy, see Burge 2003, Peacocke 2004, Sawyer and Majors 2005, andSetiya 2012: ch. 3.

The Sufficiency thesis also promises to establish rich connectionsbetween epistemology and the philosophy of mind. Consider again thedebate about high-level contents of experience. If one is able toestablish that experiences have high-level contents, one could thenuse the Sufficiency thesis to reach the conclusion that experiencesjustify beliefs in high-level contents as well.

Assuming that experiences with the content that \(p\)will give non-inferential justification for a belief that \(p\),we could then have an answer to an importantquestion for foundationalist views in epistemology. These are views onwhich our inferentially justified beliefs about the external world areinferred from a foundation of non-inferentially justified beliefs (formore see the entry onfoundationalist theories of epistemic justification). Which beliefs get to be in the foundation? This question forfoundationalist views is pressing. As Nozick remarks, it is of littleuse to have a foundation for our knowledge that is only one brick wide(1981: 3). In general, the more restrictive foundationalist views areabout the breadth of our foundational beliefs, the harder it will beto build up to everyday beliefs about the world. However, if beliefsconcerning causation, emotions, or morality get to be foundational,the foundationalist project can look much more promising (Masrour2011).

As helpful as the Sufficiency thesis could be for foundationalists, itfaces much criticism. Many objections proceed by proposingrequirements for justification that are not always satisfied when onehas an experience with a given content. For example, one might demandthat the experience be a case of seeing (section 2.2 of this entry), or demand that the experience be suitably free of top-down influencefrom one’s own mind (section 2.4 of this entry). (For further objections, see McGrath 2017 or Chudnoff 2018).

Here we will focus on objections that turn on the character ofperceptual content. The objection here is known as “the problemof the speckled hen” (see Chisholm 1942; Sosa in Sosa andBonjour 2003; Markie 2009 for different versions of the problem).

To get a feel for our problem, suppose you get a look at a speckledhen in good light, but without enough time to carefully count thenumber of speckles on it.

Figure 2. “Speckled Sussex Hennamed Mata Hari”^[2]

The objection to Sufficiency can be put as follows. First, yourexperience does have a verdict about how many spots face you—sayto the effect that \(H\) has 17 spots. Second, yourexperience does not justify you in believing that \(H\)has 17 spots. After all, forming a belief that \(H\)has 17 spots without carefully counting might manifestly seem no morelikely to be right than a guess. So, the critic concludes, someexperiences have the content that \(p\) without givingyou justification to believe that \(p\).

In response, some argue that your experience is actually silent aboutthe exact number of speckles facing you on the hen (see Tye 2009; formore on experience and numeracy, see Beck 2012).

One can raise the core challenge to Sufficiency in other ways. Anothersource of examples can be found in Block’s (2007) empiricallyinformed work on “phenomenal overflow” (drawing onSperling 1960 and Lamme 2003). Consider for example the Sperlingparadigm, in which subjects are flashed a grid of letters, and onlysubsequently given a tone that indicates which row to report (high forthe top, medium for the middle, etc). Subjects are able to report anyrow singled out without being able to report them all. (For an onlinedemo without sound, seeOther Internet Resources). Arguably subjects experience all the letters as they are withoutbeing able to report them all (but see Stazicker 2011 or Phillips 2011for criticisms of Block, also Odegaard et al 2018). The objector mayadd that we do not have justification from our experience to believethe proposition that enumerates all the letters present. (For afurther way to set up the speckled hen problem, using the example ofhighly determinate colors, see Smithies 2019: ch. 11).

Even if one allows that some experiences have enough determinacy toset up the speckled hen problem, the option remains of maintainingthat the experiences do give you justification to believe the relevantdeterminate proposition. For example, perhaps your experiences do giveyou justification to believe the determinate proposition, even thoughyou are unable to take advantage of the justification you have byforming a belief on their basis (see Smithies 2012a for a view withthis structure).

Alternatively, perhaps speckled hen cases are compatible withSufficiency since they turn out to be cases of defeat. Given that weare generally aware of our poor ability to make snap judgments aboutthe details of the scene before, perhaps we have defeasible butdefeated justification to believe detailed propositions about thescene before us.

1.3.3 Intentionalism

So far we have focused on the ramifications for epistemology of theview that experiences have propositional contents. Intentionalism is amore ambitious view in the philosophy of mind that aims to findnecessary connections between the conscious character of anexperience—what it is like to have it—and the content ofthat experience. According to intentionalists, at a minimum,

Minimal Intentionalism
If experiences \(e_1\) and \(e_2\) have the same content, then what itis like to have \(e_1\) is the same as what it is like to have\(e_2\).

In a slogan, “same content, same character” (fordiscussion of further variations in the camp, see Chalmers 2004). Onthis picture, if two experiences present the same testimony about theworld, there is no room for any difference in what it is like to havethose experiences. Whether there is such a tight link between contentand conscious character is controversial, consider the frequentlydiscussed possibility that your shifting attention could vary theconscious character of two distinct experiences without varying theirtestimony about the world.

Here we will point to some epistemological ramifications of theview.

One way to defend Intentionalism examines how we becomeintrospectively aware of what it’s like to have our experiences.Arguably we become introspectively aware of what it’s like tohave our experiences only by being aware of what we are experiencing.Perhaps awareness of the world is the sole route to introspectiveawareness of what it’s like to have a given experience. Andperhaps this point about introspection supports at least a minimalversion of Intentionalism. For further discussion of this broadlyepistemological argument for intentionalism, see the entry onqualia (section 6), also the entry onrepresentational theories of consciousness (section 3.3).

Another defense of Intentionalism examines how we become able to thinkabout certain properties by having experiences. Perhaps experiencesare sufficient for certain cognitive abilities, and perhapsIntentionalism gives the best explanation of how experiences aresufficient for certain cognitive abilities. For an exposition of thisbroadly epistemological line of argument for Intentionalism, see Pautz2010.

For an epistemological argument against some versions ofIntentionalism, see Kriegel 2011. He targets versions of the view thataim to find what constitutes experience in terms of awareness ofproperties (or a suitably similar relation to properties). Accordingto Kriegel, just as sense-data theories are unable to provide anadequate epistemology because of the “veil of appearances”they impose between perceivers and the world, the targeted versions ofIntentionalism fail to provide an adequate epistemology for the samereason. As we saw insection 2.1, sense-data theorists have ways to respond to veil objections. Perhapsintentionalists do as well.

1.4 Consciousness

1.4.1 Does consciousness play a justifying role?

An uncontroversial theory of perceptual experiences holds that theyall have a conscious character—for any experience \(e\)there is something it is like to have \(e\).Further, part of what it is for something to be anexperience is for it to have a conscious character. There is muchdebate about how to explain the nature of perceptual consciousness,but there is little debate about whether something is an experienceonly if it has a conscious character.

There is much more room for debate about the importance ofconsciousness for the epistemology of perception. One strategy ofexplaining how experiences justify beliefs focuses on their consciouscharacter. We may call it the phenomenal approach.

To see why this approach is a contender, consider subjects who have“blindsight”. They have visual representations ofwhat’s in their blind field without having conscious visualexperience of anything in their blind field (see Weiskrantz 2009 for asurvey, and Phillips and Block 2016 for a debate about whether therereally is unconscious perception). Now these subjects are better thanchance at identifying objects in their blind field, but they have tobe prompted to make a guess. For our purposes, imagine a hypotheticalblindsighted subject who does not need to be prompted to form a beliefthat there is an \(X\) to the left. Now compare thatsubject with an ordinary sighted subject who forms a belief that thereis an \(X\) to the left on the basis of visualexperience. There are various questions here whose answers mightsupport the phenomenal approach (see Smithies 2012a, 2019: ch. 3 formore).

First, is the blindsighted subject completely unjustified in believingthat there is an \(X\) to the left? If you think theanswer to this question is yes, and you’re not a skeptic aboutthe sighted subject, you arguably should be sympathetic to thephenomenal approach. What else would explain this difference betweenthem?

Second, is the blindsighted subject at any rate less justified thanthe sighted subject in believing that there is an \(X\)to the left? If you think the answer here is yes, again you arguablyshould be sympathetic to the phenomenal approach. What else wouldexplain this epistemic difference between them?

In response, one might deny that the epistemic differences obtain (seeLyons 2009, also Berger 2020). Even if one accepts that the epistemicdifferences obtain, one might still insist that they are equally orbetter explained by alternative candidates than consciousness. Forexample, perhaps the blindsighted subject does not count as seeing the\(X\), and perhaps the sighted subject is morejustified than the blindsighted subject simply thanks to seeing the\(X\) (as an \(X\)). Here theexplanatory burden would be borne by bearing a perceptual relation tothe thing, rather than having an experience with a certaincharacter.

Here it might help to compare the sighted subject with a conscioussubject for whom things are just the same from the inside, but whofails to see any \(X\) because she is hallucinating. Ifthe sighted subject and the hallucinating subject are equallyjustified in believing there is an \(X\) to the left,visual experience might be a better candidate than seeing to explainthe epistemic symmetry between the sighted and the hallucinatingsubjects.

Suppose the blindsighted subject and sighted subject are equallyjustified—is the phenomenal approach then doomed? Speakingloosely, even if the blindsighted subject has the same epistemiceffect as the sighted subject, it’s not entirely clear thatthere must be the same cause (or perhaps there is a common unconsciouscause present even in the sighted subject).

To support the claim that consciousness doesn’t supplyperceptual justification, one might look to other real-life cases ofunconscious visual representation. One sort of case is that ofunconscious priming. Here you are exposed to a stimulus too quicklyfor it to register in visual experience, but for all that it stilldoes affect your behavior. For example, an unconsciously registerednumeral might improve your ability to report that a subsequently seennumeral is greater or lower than 5, depending on whether the primingone is itself greater or lower than 5 (Naccache and Dehaene 2001). Nowthis sort of case is arguably not one in which unconscious visualrepresentations justify. The subjects concerned plausibly do not formbeliefs that are good candidates to be justified by their unconsciousvisual representations. But consider people with visual hemi-neglect,who seem to lack conscious visual experience of their neglectedfield.

Some neglect patients seem to take in information about the neglectedstimuli, and to form beliefs about it. For instance, some of them,when presented with a burning house in their neglected field and anormal house in their normal field, prefer the one that isn’t onfire (Marshall and Halligan 1988; Bisiach and Rusconi 1990). Here theydo form a belief that is a candidate to be justified by theirunconscious visual representation. Their belief that the house intheir neglected field isn’t preferable might be justified by theinformation they take in, even if the intake is through unconsciousperception. If this case is one in which the subject is justified, andjustified to the same degree as in ordinary cases of consciousperception, one might then start to wonder whether consciousness mustplay a role even in ordinary cases of perceptual justification.Perhaps it is side-stepped by unconscious visual representations eventhen.

1.4.2 What aspect of consciousness plays a justifying role?

If the conscious character of experiences does play a justifying role,a further question remains about why it does so. One might hold thatthere is no further explanation to be provided here. Perhaps thecapacity of consciousness to justify is a fundamental fact ofepistemology. According to another proposal, consciousness justifiesthanks to being introspectively accessible. On this internalistconception of justification, a special kind of access to a source isnecessary for the source to provide justification, and consciousnessstands out for allowing this sort of access (see e.g. Smithies 2012b,2019).

Here we will focus on a particular aspect of the conscious characterof experiences, one highlighted by Pryor (2000) among others. To get afeel for this feature if you are sighted, first look away from thissurface and imagine a black circle in front of you. Now look at thissurface and have a visual experience of the black circle in front ofyou constituting the period ending this sentence.

In the former case, you were not justified in believing that there isa black circle in front of you. In the present case, you are. Onecandidate way to explain the epistemic difference is to focus on adifference between what it is like to imagine and what it is like tohave a visual experience (see Martin 2002 for more).

The salient feature of experience here is not easy to pin down. Therough idea is that, when you visually experience, as opposed to whenyou visually imagine, things are presented to you as actually beingthe case. How this feature of experience is best to be understood isopen to debate. For now let us leave open its exact nature and simplyuse the term “presentational phenomenology” as aplace-holder for whatever it is (for more elaboration see Chudnoff2012 or Bengson 2015, and see Teng 2018 for a challenge to privilegingpresentational phenomenology).

Even if presentational phenomenology is epistemically privileged,there remains an important question about its scope. Suppose you see acow through a picket fence. There is arguably some way youperceptually “get” that there is an extended cow there.For a dramatic contrast, start by considering Damien Hirst’sSome Comfort Gained From the Acceptance of the Inherent Lies in Everything, that consists of a cow vertically sliced into a series of boxesarranged like dominos. Now suppose you know you are seeing the Hirstsculpture through a picket fence, where the segments align exactlywith the gaps in the fence. Here you arguably would not perceptually“get” that there is an elongated cow there.

In the ordinary case of seeing a cow through a picket fence, it isdebatable whether presentational phenomenology includes the presenceof an extended cow, or whether it includes only those regions of thecow not occluded by the fence (see Noe 2005 for further discussion).If your presentational phenomenology includes only the non-occludedregions, and only presentational phenomenology supplies perceptualjustification, the rational powers of experience threaten to belimited. You would not have justification to believe that an extendedcow is present just by taking your experience of the cow through theslats at face value. Analogously, if only the facing surface of anobject is phenomenally present, you might have justification tobelieve only that the facing surface is present by taking yourexperience at face value. Here we might find ourselves back at the“veil of surfaces” discussed insection 2.2.

Some might accept this prediction. In his 2018a and 2018b, Chudnoff ineffect does. He compares seeing an ordinary occluded dog with seeingan unfamiliar occluded blob, and claims that our visual experience insuch cases has presentational phenomenology only with respect to whatis not occluded, and gives us immediate justification for beliefs withrespect to only what is not occluded. On his view, our backgroundinformation about dogs picks up the slack to enable us to have ajustified belief about the full shape of the dog, whereas nobackground information is available for us to have a justified beliefabout the full shape of the occluded blob. In response, Helton andNanay 2018 in effect argue that Chudnoff’s view threatens tolead to skepticism about ordinary beliefs about occluded objects, andunderestimates the powers of visual experience with respect to noveloccluded objects. To avoid potential skeptical problems, some mayprefer to take a more expansive view of presentationalphenomenology.

1.5 Degreed Perception

We have spoken so far about experiences justifying beliefs in an allor nothing way. As Munton 2016 reminds us, visual experiences canjustify the same belief to differing degrees. For example, suppose youare looking outside at the park on a foggy and snowy morning, andgradually get a better view of a new snowman as the fog clears. Hereyour successive visual experiences of the snowman justify your beliefthat there is a snowman in the park more and more as the fog clears.Perceptual justification comes in degrees.

A caution about how to set up the issue is in order. If you think thatperceptual justification is only binary and does not come in degrees,you should avoid the following common formulation of that sort ofview: either your experience justifies a belief that there is asnowman in the park or it does not. We can all agree that the law ofexcluded middle applies to perceptual justification, thatdoesn’t yet rule out the possibility that perceptualjustification comes in degrees. For example, perhaps your experiencejustifies a belief when the degree of justification it gives issufficiently high, and otherwise not. This is a scenario in which yourexperience either justifies a belief or it does not, as well as ascenario where perceptual justification comes in degrees.

According to Munton, we can now draw a conclusion about the nature ofvisual experiences, in effect using the template we have surveyed sofar (I focus on Munton’s argument because she puts epistemologyfront and center. A related argument by Morrison 2016 instead focuseson variations in what happens when we form opinions by completelytrusting our experiences, but this argument departs from psychologyrather than epistemology).

As a first pass we can try the following:

Epistemology2
Our experiences justify beliefs about the externalworld to varying degrees.

Epistemology-Mind Link6
If our experiences justify beliefs about theexternal world to varying degrees, then our experiences are themselvesdegreed.

So,

Mind3
Our experiences are themselves degreed.

The conclusion that experiences are degreed is striking and important,but it can be elaborated in quite different ways.

One choice point is where to locate potential variation in degrees.One option would be in the contents of the experiences, another wouldbe in the mental relation we bear to contents or to the world inhaving an experience (variation in principle could be located in thevehicles of experiences as well or somewhere else). A further choicepoint is about how to understand variations in degrees of experiences.A tempting option is to piggyback on probabilistic theorizing aboutcredences or degrees of belief (but bear in mind that in principleexperiences could be degreed without being degreed in a probabilisticway). The idea here is to cash out the idea that experiences aredegreed in a similar way to how philosophers cash out the idea thatcredences are degreed (without necessarily saying that experiencessimply are credences). So just as you might have a higher credencethat the 4-sided die will land 4 than the 6-sided die might land 4,perhaps you also have a higher visual credence that there is a snowmanout there when the fog is lighter, as opposed to when the fog isheavier. Now, how to understand credences themselves is open todispute, where again dimensions of variation might be located indiffering mental relations to the content that the die will land 4, orpotentially instead in different contents concerning 1/6 probabilitiesas opposed to 1/6 probabilities. Also, even if credences arethemselves best understood in probabilistic terms, that is not yet tosay that credences are best understood specifically in Bayesian terms.So degreed views of experience aren’t forced to commitspecifically to Bayesian views of perception (for more onprobabilistic views of perception, often focusing more on theprocesses leading to perception rather than what is generated by thoseprocesses, see Hohwy 2013, Rescorla 2015, Siegel 2020, or Vance 2021).Understanding degreed experiences along the lines of credences opens awide menu of options.

For a final complication, note that there is extensive debate aboutthe relation between traditionally conceived beliefs and credences.One eliminativist option ultimately denies that there are beliefs,replacing them with credences. Other approaches keep both beliefs andcredences in the picture, and understand beliefs in terms ofcredences, or credences in terms of belief, or neither in terms of theother (see section 4 of SEP entry on formal representations ofbelief). Likewise, once one has admitted experiences that are degreedsomehow in the manner of credences, one might at the same time stillallow for other experiences more like traditionally understoodbeliefs. So there is now room for the questions about the relationbetween beliefs and credences to play out in the case of experiencesthat are structured along the lines of beliefs vs. degreed experiencesstructured along the lines of credences. Perhaps there only aredegreed experiences structured like credences, or perhaps there arealso experiences structured like beliefs, where we can ask whethereither of the two entities has explanatory priority in relation to theother.

In sum, understanding experiences as being degreed in the manner ofcredences is a fascinating line of research, but also a multi-prongedone given the extent range of questions about credences.

Now that we’ve seen some of the possibilities that arise ifexperiences are degreed, the question remains of whether the epistemicargument above establishes that any of them is actual.

In order to make the needed link from epistemology to mind plausible,the linking premise and the rest of the argument need to be refinedright away. The strategy is to trace variation of degrees injustification to variations of degrees in experience, but rivalcandidates for explaining the variation need to be blocked. For all wehave said so far, the variation in degrees of justification could betraced not to experiences, but rather to differing degrees ofjustification to believe that your experiences are trustworthy(depending on the conditions of fog).

To block a role for differences in your background beliefs, Munton ineffect focuses on immediate justification for your experiences (usingthe terminology of “direct” justification). This gives usthe following

Epistemology3
Our experiences immediately justify beliefs aboutthe external world to varying degrees.

Epistemology-Mind Link6
If our experiences immediately justifybeliefs about the external world to varying degrees, then ourexperiences are themselves degreed.

So,

Mind3
Our experiences are themselves degreed.

Even given these refinements, rival explanations still need to beblocked. For example, perhaps the new version of Epistemology isfalse, and experiences only provide specifically immediatejustification in optimal cases (for discussion see Munton 2016). Orperhaps the new version of Link is false, and the variations indegrees of justification can be explained in line with a traditionalnon-degreed picture of what experiences are. For example, considerthat your experience plausibly concerns not just the potential snowmanin the park, but also the amount of fog in the park and other aspectsof your viewing conditions. And consider the phenomenon of defeat,where information you receive can reduce or destroy the amount ofjustification given by your experience. Given that your experience ineffect takes a stand on the quality of your viewing conditions,perhaps your experiences in higher conditions of fog undermine thedegree of justification they supply specifically to believe a snowmanis there. Here we might explain the variation of degrees ofjustification through variation in the experience, but through gardenvariety non-degreed perceptual content concerning viewing conditions,rather than any more striking degreed character of the experiences(this sort of objection is discussed further in Beck 2020).

We have now surveyed the epistemic implications of some centraltheories of experience. We have by no means covered all theories ofexperience. Here we will simply point to further important areas toconsider. For discussion of naïve realist theories of experience,and of their interaction with issues about skepticism, see the entriesonepistemological problems of perception andthe disjunctive theory of perception. For discussion of how dualist theories of experience might lead toepiphenomenalism, where epiphenomenalism might lead to skepticalproblems, see the entry onepiphenomenalism (section 2.3). For discussion of the theory that experience isactually a special case of belief, where that theory might affect ourunderstanding of how we base beliefs on experiences, see the entry onthe contents of perception (section 2.2).

2. Perceptual Phenomena

Let us now consider the significance for epistemology of a range ofperceptual phenomena. On most views, these phenomena do not occur inall cases of perception, but still have important ramifications forthe epistemology of perception.

The first array of phenomena are concerned with the relation betweenexperience and the world. Here we will consider different kinds ofperceptual error, as well as forms of perception that occur only inthe absence of error. The remaining phenomena we will consider arecharacterized by the internal etiology of experience. Here we willlook at the influence of attention and of other mental states on ourexperience.

2.1. Perceptual Error

2.1.1 Illusion and Hallucination

In cases of perceptual error, we form a false belief on the basis of amisleading experience, as when an uninformed subject concludes thereis motion below (to get the effect, let your eyes drift over theimage):

Figure 3. “Rotating snakes”^[3]

This is a paradigm case of an illusion, where you do see a scene, butmisperceive what the scene is like. In a paradigm case ofhallucination, you have a perceptual experience, but do not perceiveanything in the scene before you.

Few dispute that there are cases of perceptual error (although somedisagree about whether perceptual error is ever properly at the levelof experience as opposed to that of beliefs formed on the basis ofexperiences, cf. Brewer 2006). Many skeptical arguments use theoccurrence of perceptual error to conclude that experiences do not doa particular job in epistemology. We can understand these arguments asusing different versions of the Epistemology-Mind Link:

Epistemology-Mind Link7
If experiences sometimes deceive us, then experiences do not give usknowledge of the external world.

Epistemology-Mind Link8
If experiences sometimes deceive us, then experiences do not give usjustified beliefs about the external world.

For discussion of how to supplement or defend such principles, see theentries onskepticism andepistemological problems of perception.

Here we will focus on a weaker principle that addresses the kind ofjustification we can get from perceptual experiences:

Epistemology-Mind Link9
If experiences sometimes deceive us, then experiences at best give usinferential justification for beliefs about the external world.

If our experiences sometime deceive us, there is a “gap”between our having of the experience and the truth of the propositionthey putatively justify. On E-M Link9, some intermediate belief willthen be needed to close the gap between experience and truth, forexample a belief to the effect that our experiences are reliable.Given the need for an intermediate belief, our experiences will thenarguably fail to give us non-inferential justification for beliefsabout the external world. This conclusion is endorsed by somephilosophers who still reject skepticism about perceptualjustification (Cohen 2002; Wright 2004; or White 2006).

E-M Link9 might still lead to skepticism. Consider an auxiliary beliefmeant to bridge the gap between experience and truth, and ask whetherwhatever process that lead to it might sometimes deceive us. Forexample, consider your belief that your experiences are reliable, andwhatever process led to your belief that your experiences arereliable. That process could arguably lead you to falsely believe yourexperiences are reliable in a situation where you are radicallydeceived by an evil demon.

We now have a gap between the occurring of the process that led to anauxiliary belief and the truth of the auxiliary belief. So then,according to the reasoning behind E-M Link9, we would need anotherauxiliary belief to bridge the gap. Since an evil demon couldpresumably deceive us yet again, a threat of vicious regress ariseshere ((White 2006 articulates this line of thought without endorsingit (or explaining where it goes wrong)).

2.1.2 Dreaming

We have considered the significance of illusion and hallucination.Let’s now examine the case of dreams. Dreams are oftenunderstood to be paradigms of perceptual error, for example byDescartes when, discussing his apparent perceptions, he writesthat

this would not happen with such distinctness to someone asleep.Indeed! As if I did not remember other occasions when I have beentricked by exactly similar thoughts while asleep! (PW, p. 13)

The picture of dreaming as a case of perceptual error is challenged bySosa (2005).

We can frame the issue with a simplified argument for skepticism:

Epistemology-Mind Link10
If our experiences justify beliefs about our present surroundings, ourexperiences do not frequently deceive us while we dream.

Mind4
Our experiences frequently deceive us while we dream.

So,

Not-Epistemology
Our experiences do not justify our beliefs about our presentsurroundings.

Sosa responds (to a more complex skeptical argument focused onknowledge) by defending an alternative conception of dreams known as“the imagination model”. According to the imaginationmodel, we actually do not form beliefs about our surroundings when wedream, or even have perceptual experiences when we dream.

In defense of the imagination model, consider that, when I go to bed,I form and store a belief that I am lying in bed. If I were to form abelief while I am dreaming that I am running away from lions, I wouldthen have a belief that contradicts my stored belief that I am lyingin bed. Now we arguably do not have such contradictory beliefs whilewe are dreaming. The view that we form beliefs while dreaming mightthen be what has to go (Sosa 2005: 6).

Let’s now consider the case of visual experience. On theimagination model, when dreaming we do not even have visualexperiences with the same conscious character as those we have whenawake (we leave open whether we have “visual experiences”while dreaming in some extended sense). The argument at this stage canexploit the earlier conclusion that we do not form beliefs about oursurroundings while dreaming. Sosa defends the further thesis on thegrounds that, if we did have experiences when dreaming with theconscious character of those we have when awake, we would be open toepistemic criticism for failing to form beliefs that take ourexperiences at face value. However when I dream that I am beingattacked by a lion, but do not believe while I dream that I am beingattacked by a lion, I arguably am not open to epistemic criticism.

If the imagination model of dreaming is correct, the skepticalargument above is unsound because Mind is false. For discussion ofwhether Sosa succeeds in blocking the best dreaming arguments forskepticism, see Ichikawa 2009. For further discussion specifically ofthe visual character of dreams, see Schwitzgebel 2011: ch. 1.

2.2 Successful Perception

Some epistemologists privilege perceptual states that you are in onlyif you are not in cases of illusion or hallucination. On their views,these states are either the only sources of perceptual justification,or at any rate the best sources of perceptual justification. In theterminology of Hawthorne and Kovakovich 2006, we may call theseperceptual states “success states”.

To get a sense of some of the candidate states, consider the followingtable:

Epistemologists differ according to which success states theyprivilege, what job they assign to the state, and how severely theyregard the absence of the privileged state.

For views which privilege seeing that \(p\), seeMcDowell (1982, 1995) or A. Jackson (2011). For views which privilegesomething along the lines ofseeing \(a\)’s \(F\)ness, seeJohnston (2006). These states arefact-entailing, since as a matter of necessity, you see that\(a\) is \(F\), orsee \(a\)’s\(F\)ness, only if \(a\)is in fact \(F\). For a view thatpotentially favors the sort of perceptual state you find in cases ofvision and illusion rather than hallucination, see Burge (2003). Thissort of state isrelational, since you can be in it only ifthe relevant object of perception is present in your scene. Assumingthat each conscious success state has a counterpart in unconsciousperception, notice that versions of these views might focus onperceptual states in common between conscious subjects and subjectswithout conscious perception.

In principle, you might get perceptual justification from a successstate in the good case of vision or illusion, and get the same amountof perceptual justification from a non-success state in the bad caseof hallucination (Lord forthcoming takes up a view with this structureregarding reasons for belief). We bracket that sort of approach here.It is more common to hold that you get no perceptual justification inthe case of hallucination (e.g., Jackson 2011), or at least a lowerdegree or different kind of perceptual justification in the case ofhallucination (e.g., Schellenberg 2013).

Let’s group views that privilege success states under the label“Success Theory”, and leave open how to adjudicate withinthe camp.

In support of Success Theory, one can emphasize the tight connectionthe approach draws between perceptual justification and truth. On manyversions of the approach, the state that gives you justification tobelieve that \(a\) is \(F\) guaranteesthe truth of the belief that \(a\) is \(F\).Moreover, the source of your justification remainsmental and arguably accessible to you, thus satisfying the demands ofsome “internalist” approaches in epistemology thatprivilege what is inside the subject or accessible in a special way bythe subject (Prichard 2012). Moreover, Success Theory has a promisingconnection with issues about skepticism. They promise to blockskeptical arguments that assume our evidence is the same between thegood case of successful vision and the bad case of radical deceptionor hallucination (McDowell 1995, for a critique, see Wright 2004).

As an objection to Success Theory, many bring in demands onjustification that are not satisfied by the most versions of the view.For instance, consider the internalist thesis that, if things seem thesame to each of two people from the inside, then those two people areequally justified in their beliefs. More specifically, if two peoplehave the same conscious perspective on the world, and the same storedbeliefs, then they are the same with respect to the degree ofjustification of their beliefs. This sort of thesis is often motivatedby considering radically deceived counterparts to us, and appealing tothe intuition that such subjects and us are equally justified (Lehrerand Cohen 1983; Cohen 1984; Wedgwood 2002; for dispute, see Sutton2007 or Littlejohn 2012). Now, if a version of Success Theory predictsthat a subject in perceptual error has less justification than acorresponding perceiver, that version might be rejected on the basisof its conflict with the internalist thesis.

In response, one might attempt to explain away the intuition of equaljustification as instead concerning equal blamelessness orexcusability, or at any rate as being correct only if restricted toblamelessness or excusability (e.g. Williamson 2007 or forthcoming).Critics often try to respond by distinguishing the sort ofblamelessness or excusability one finds in cases of cognitive delusionor brainwashing, from the epistemic status of the beliefs of thevictim of an evil demon (Pryor 2001), or by demanding a more thoroughexplanation of why the victim is indeed blameless or excusable(Miracchi forthcoming). Recent literature also steps back to examinewhether a substantive distinction can be drawn between justificationand excusability, surveying potential distinctive explanatory rolesfor epistemic excuses to play (Greco 2019).

Alternatively, someone with a “disjunctive theory ofperception” might insist that the radically deceived subjectdoes not have the same conscious perspective on the world as thesuccessful perceiver (Fish 2013, also the entry onthe disjunctive theory of perception). On this line of thought, to have the conscious perspective of someonein a case of perceptual success, you need to be in a case ofperceptual success. Here the antecedent of the internalist thesis isnot satisfied in cases of radical deception. One challenge here isthat there are many ways to be deceived. For example, when someonesees that a lemon is yellow, they might well lack a consciouscounterpart who hallucinates, but they arguably still have a consciouscounterpart who sees a fake lemon that is yellow. If the subject in acase of vision and the subject in a case of illusion are equallyjustified, that will be trouble for approaches that give justifyingprivilege to the states of seeing that \(a\) is \(F\)or seeing \(a\)’s \(F\)ness.

Some philosophers might attack Success Theory on the grounds that itis too internalist rather than not internalist enough. According totheorists such as Ginsborg 2006 or Roessler 2009, the justifiers ofperceptual beliefs are best understood to be facts about the externalworld rather than facts about perceivers’ mind.

2.3 Attention

Standard cases of perceptual justification are ones in which youattend to what you see, as when you attend to your mail and form ajustified belief that you have mail. But are all cases of perceptualjustification ones in which attention is involved? According to theAttention Needed view, only attentive experiences can providejustification. According to theAttention Optional view,inattentive experiences can provide propositional justification.

If you only experience what you attend to, as is maintained byphilosophers such as Prinz 2012, all cases of justification byexperience will trivially involve attention as well. Here we’llpursue the issue on the assumption that we sometimes experiencesomething we do not attend to, as is held by theorists such as Searle1992 and Mole 2011.

To make our discussion concrete, consider Simons and Chabris’s(1999) famous “Selective Attention Test” on youtube (seethe link inOther Internet Resources). When subjects were asked to count passes of basketballs—spoileralert!—a fair number failed to notice a person in a gorilla suitwho came into the scene. Given how hard it is to track the passes ofbasketballs, it is natural to assume that the non-noticers wereattending only to the basketballs, and did not attend to the person inthe gorilla suit. Now suppose that some of non-noticers still didexperience a person in a gorilla suit in the scene, as a person in agorilla suit. According to the Attention Needed view, theirinattentive experience cannot provide them with justification tobelieve that someone’s there in a gorilla suit. According to theAttention Optional view, their inattentive experience might stillprovide them with justification to believe that someone’s therein a gorilla suit.

Both views have their attractions. Typically, if you look carelesslyat a scene, your experience will put you in a worse epistemic positionif you look attentively at the scene. Perhaps if attention is fullygone but experience remains, experience no longer providesjustification.

On the other hand, you can have evidence you don’t notice youhave, and this point might favor the Attention Optional view. Considereveryday cases of “change blindness” discussed by Dretske2004. For example, your friend gets a haircut, and asks you “doI look different?” You are stumped. On Dretske’s account,you might still have a perfectly accurately experience of how his hairnow looks. Here your experience plausibly gives you justification tobelieve that your friend got a haircut (when combined with yourbackground beliefs). You also fail to notice that your experiencegives you justification to believe your friend got a haircut. Ifexperiences provide un-noticed evidence, such cases are arguably goodprecedents for the sorts of cases allowed by the Attention Optionalview. (For striking cases of change blindness, see the link inOther Internet Resources.)

For further discussion of the potential epistemic roles of attention,see Campbell 2002, 2011; Roessler 2011; Smithies 2011; Wu 2014; andSilins and Siegel 2014.

2.4 Cognitive Penetration

According to one empiricist tradition, experience functions as amirror, reflecting what is before the subject, without anymanipulation by the subject’s mind. Given that experience issupposed to not be influenced by one’s theories or expectations,it is thereby supposed to be in an optimal position to confirm ordisconfirm hypotheses about the world. According to a wide range ofphilosophers and scientists, such a picture of the nature ofexperience is mistaken, putting limitations on the ability ofexperience to justify belief. In the philosophy of science, thechallenge has been put in terms of the “theory-dependence ofobservation”, and the implications thereof. In more recentepistemology and philosophy of mind, the challenge has been put interms of “cognitive penetration” or “top-down”effects and the implications thereof.

To survey the debate, we’ll start with the philosophy of mind byconsidering potential examples of the phenomenon, and we will thenturn to questions in epistemology.

One potential source of examples comes from ambiguous figures such asthe Necker cube (Hanson 1958; Kuhn 1962; Churchland 1979, 1988).

Figure 4. Necker Cube^[4]

You can see this figure as a downward-tilted cube with the left faceclosest to you, or as an upward-tilted cube with the right faceclosest to you. Critics dispute whether such examples support anythesis oftheory-dependence of observation. An alternativeresponse is that you experience the figure in different ways merelybecause you attend to different parts of the figure at differenttimes. Here the difference in your experience is not explained bydifferences in what theory you hold (Fodor 1984).

Theorists such as Hanson, Kuhn and Churchland also made much of workby so-called “New Look” psychologists such as Bruner andPostman. Consider for instance Bruner and Postman’s classic 1949experiment involving anomalous playing cards. In this experiment,subjects were briefly shown the following sort of card:

Figure 5

What did you just see? When subjects were exposed to this sort ofcard, many reported it to be a six of hearts. The card is actually ared six of spades.

One might claim that the card looked to you the way red sixes ofhearts look to you. However, there is much skepticism about whetherthere is an effect here on perceptual experience itself (Fodor 1983;Pylyshyn 1999). Perhaps the card fails to look like a red six ofhearts to you, and you simply jumped to the conclusion that it is ared six of hearts when you form your belief. The effect might merelyhave been on beliefs formed on the basis of perceptual experience.

The current debate about cognitive penetration is informed by morerecent experiments in psychology. For a case of a top-down effect inthe current literature, consider “memory color” in Hansenet al.’s banana (2006). When subjects were asked to adjust animage of a characteristically yellow object until it was achromatic,they overcompensated by adjusting until the image was slightly bluish.Subjects did not overcompensate with objects that were notcharacteristically yellow. The type of case presented by Hansen et al.is much harder to explain away as not really involving top-downeffects than those in the classic philosophy of science literature.(For related examples, see Delk and Fillenbaum 1965 or Olkkonen,Hansen, and Gegenfurtner 2008. For further discussion of whether andhow there might be top-down effects on perception, see Macpherson2012, Deroy 2013, Firestone and Scholl 2016; Green 2020).

Let us now turn to the epistemology of cases of cognitivepenetration.

It’s not clear whether all cases of top-down effects areproblematic for perceptual justification. Consider the possibility oftop-down effects from expertise. For example, perhaps the expertradiologist sees more than the novice when looking at an x-ray, andperhaps the expert chess-player sees more than the novice when lookingat a chessboard in mid-game (see the papers in Ericsson 2006 fordiscussion of such examples). Further, suppose that the expertiseexamples are genuine cases of top-down influence. Here the expert ispresumably at an epistemic advantage thanks to top-down effects, whereher experience justifies her with respect to those contents that herexperience has thanks to her cognitive background (Siegel 2012).

To see why some cases of top-down effects might be epistemicallyproblematic, consider Siegel’s (2012) hypothetical case of“Angry Looking Jack”. Suppose that Jill antecedently hasan unjustified belief that Jack is angry at her. The next time shesees him, he does look angry to her—as a result of a top-downeffect from her belief. In response to her experience, Jill thenreaffirms her belief. Is she now justified in believing that Jack isangry at her? (Markie 2005 presents a related example of a goldprospector whose wishful thinking makes a nugget visually seem to begold).

If you are inclined to deny that Jill’s belief is justified, you couldappeal to an intuition that Jill is not justified by her experience inbelieving that Jack is angry at her (Siegel 2012). But others may notshare the intuition.

Another strategy is to give a further argument that Jill is notjustified by her experience in believing that Jack is angry at her.For arguments that appeal to an analogy with the unjustified formationof a belief on an unjustified belief, see McGrath (2013) and Siegel(2013) (Teng 2021 critically responds). For an argument that appealsto an analogy with the unjustified formation of beliefs on the basisof emotion, see Vance (2014).

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Other Internet Resources

• Selective Attention Test (demonstration of “inattentional blindness”).
• The Door Study (demonstration of “change blindness”).
• Sperling Demo, hosted on Ned Block’s page, New York University.
• Akiyoshi Kitaoka’s illusion pages, Professor, Department of Psychology, Ritsumeikan University, Kyoto,Japan.

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Acknowledgments

Many thanks for their help to David Chalmers, Andrew Chignell, FionaMacpherson, Neil Mehta, Susanna Siegel, the SEP administrativeeditors, and two SEP referees.