Pete Mandik
Philosophical thought on the nature of perception occupies some of the most significant concerns in the history of philosophy. At first, perception may seem quite simple. Right now I am perceiving my coffee mug. I open my eyes, look at the mug and see it. What could be simpler? The mug is there, I am here, there’s no obstruction between us in this clean, well lit room, thus, I have no difficulty seeing the mug: I perceive it visually. And I may reach out and grasp it, thus perceiving it through sense of touch. Just as there is nothing between me and the mug to prevent me from seeing it, there is no obstruction between me and the mug to prevent me from reaching out and feeling it. Likewise, I may smell and taste the coffee contained therein, and dropping the mug, there may be plenty for me to hear as well. Philosophical reflection renders things much more complicated, however. While common sense may say that there is nothing between me and the mug to prevent me from seeing it, much philosophical thought on the matter has led to the view that my mind itself gets in between me and the mug and that I never actually perceive the mug itself, but only states of my mind that at best, represent the presence of a mug. But the mug itself, a thing that exists independently of my mind, is necessarily and permanently beyond the grasp of my mind.
Such a view goes far beyond common sense and may strike the untutored reader as absolutely absurd. Indeed, many professional philosophers have sought to defend common sense on this regard. Philosophical controversy on the matter rages on even today, and the core issue may be summed up thus: Do we perceive anything besides the states of our own minds? If so, how? If not, why not?
In the history of these philosophical debates, we may discern three main kinds of philosophical theories of perception: direct realism, indirect realism, and idealism. Before going on to describe these three kinds of theories, it will be helpful to first describe the contrasts between directness and indirectness and between realism and idealism.
The issue at stake regarding the question of whether perception is direct or indirect is difficult to pin down precisely, but at a minimum it involves the question of whether the objects we typically take ourselves to be aware of—for instance, when through vision we become aware of a chair—are objects that we are aware of only in virtue of being aware of something else. For an indirect theorist, I am not directly aware of the chair—I do not directly perceive the chair. I am aware of the chair only in virtue of being directly aware of some state of my mind. So, on one standard way of being an indirect theorist, one might say that I have a perceptual idea or perceptual mental representation in my mind that I am directly aware of, and I use that representation as the evidential basis for an inference that there is some object external to me—a chair—that is the cause of this representation, and I am thereby indirectly aware of the chair. Whatever indirectness ultimately amounts to for a particular indirect theory of perception, at a minimum it involves the idea that one is perceptually aware of external objects only in virtue of being aware of some internal object.
In contrast, direct theories of perception allow that one may be directly aware of external objects, that is, for instance, one may be aware of chairs without necessarily being aware of some state of their own mind. This is not to deny that perceivers have internal states. Nor is it to deny that perceivers are aware of the external world in virtue of having internal states. What the direct theorists deny is that a person needs to be aware of his internal states in order to be aware of the objects and properties in the external world.
One way to get a grip on the notion of indirectness at play is by analogy to the things we see when we watch television. If I am watching David Letterman on TV, there is a relatively clear sense in which I am perceiving David Letterman. There is also a relatively clear sense in which I am perceiving David Letterman only indirectly in virtue of perceiving the images on the screen of the television: my perception of David Letterman is less direct than my perception of the images on the screen in virtue of which I perceive Letterman. For the indirect theorist, normal visual perception is like watching a TV in your head with the mind’s eye: we “see” images in the mind more directly than the objects in front of our face.
It is crucial to keep in mind the prima facie compatibility of direct theories of perception with contemporary cognitive science. Recall that one of the crucial tenants of cognitive science is that the mind works in virtue of mental representations and computations that manipulate mental representations. One must caution against inferring that perception is indirect from the mere fact that perception involves mental representations of the objects perceived. Direct theories need not deny that perception involves mental representation: what they deny is that perceiving an external object involves first perceiving one’s own mental representations. Thus it is important to realize that even in the context of cognitive science the question of whether perception is direct or indirect remains open. Representational theories of perception are not necessarily indirect theories of perception. Much confusion to the contrary is due to the historical practice of calling indirect realism “representational realism”. In other words, directness in the theory of perception should not simply be equated, without argument, with the involvement of representations in perception.
We turn now to realism and idealism. In general, to be a realist (in the philosophical sense of the term) about some thing is to hold that the thing exists and further, that it exists independently of your mind. Thus one is a realist about electrons insofar as one affirms that there are indeed electrons, and that there would be electrons even if no one held the opinion that there were electrons. Likewise, one may be a realist about properties as well as objects. So, one is a realist about the property of being purple if one affirms that there really are things that are purple and whether things are purple does not depend on anyone perceiving things as being purple. (there is a further wrinkle that we will not go into here , but briefly mention: property realism is sometimes identified with the view that properties exist over and above the things that have them, so, the property of being purple would exist even if nothing were actually purple at some particular time.) Now, to be an idealist about some thing is not to deny the existence of that thing, but instead to assert that the thing's existence is mind-dependent. Likewise for idealism about properties. So, the common maxim that beauty is in the eye of the beholder is an expression of idealism about beauty. It does not deny that any one or anything is beautiful, but instead asserts that whether something is beautiful depends on someone’s mind. More specifically, whether something is beautiful depends on whether someone perceives it as beautiful.
The role that the notions of realism and idealism play in theories of perception concerns the objects we take ourselves to perceive and the properties we take those objects to have. To illustrate this in terms of an example, consider your visual perception of some piece of denim, or more specifically, your perception of the denim as being blue. A realist about color would say that the blueness of the denim is a property that does not depend on our minds: it does not depend on our perceptions of blueness. An idealist about color, in contrast, asserts that blueness is in the eye o the beholder. According to such an idealist, a world without perceivers would be world without colors. Many readers may be familiar with the way of poking fun at philosophical debates that asks “If a tree falls in the woods and no one is around to hear it, does it make a sound?”. The idealist about sounds answers “no”: sounds do not exist if there is no one around to hear them. The realist answers “yes”: sounds exist mind independently, and don’t depend on anyone to hear them for their existence.
Perhaps the most crucial aspect of the debate between realists and idealists concerns the ontological status of the properties that we perceive objects as having: Do the objects retain these properties even when unperceived? In a clean well lighted room I perceive my coffee mug to be blue. When no one is around or the room is pitch black, is the mug still blue? For perceptual realists , the properties we perceive objects as having persist unperceived. For idealists, they do not.
For direct realists, the objects external to us that we typically take our selves to perceive—tables and chairs, rocks and trees—are both directly perceived and retain their perceived properties even when unperceived. I am not aware of what a dog looks like only by first being aware of some mental representation of a dog. This is not to deny that we may sometimes become aware of our own mental representations. Right now I am thinking about the Eiffel Tower, and am quite self-consciously aware that I am mentally representing the Eiffel Tower. And if I were standing in front of the Eiffel Tower and visually perceiving it, I may perhaps pause to reflect on the act of perception itself, and thereby become aware of my own mental representation of it. But what the direct realist is denying is that this self-awareness is a necessary component of perception.
Direct realism is perhaps the closest to the common sense view of perception. The world is there for us to see directly and we are capable of seeing it for what it really is. And the way we see it is the way it is even when we are not looking. We turn our backs on objects and they do not vanish. We pack our clothes into a suitcase and they retain their colors and textures even though we take a break from perceiving them. For various reasons philosophers have called this version of direct realism “naïve realism”. Primary among these reasons is the belief that science has shown that many of the properties we perceive objects to have are not really instantiated by objects independently of our perceptions. One example might be the perceived solidity of a table. I knock on it with my knuckles and it feels quite solid. I set books on the table and they do not pass through it. But science tells us that the table is mostly empty space: the microscopic particles that constitute the mass of the table occupy only a tiny fraction of volume that the table occupies.
A traditional way of spelling out scientific realism is in terms of a distinction between primary properties and secondary properties. According to philosophers who believe that there is such a distinction to draw, primary properties—typically shape and size—persist unperceived and do not depend on perceivers for their existence. Secondary properties—typically colors, tastes, and odors—do not persist unperceived, or if they do, are regarded as not having an existence independent of perceivers. One way of regarding colors as secondary properties is to regard them as powers to elicit certain responses in perceivers. According to some philosophers, just as we do not regard pain as residing in the pin that pricks us, nor should we regard yellowness as residing in the flower that looks yellow. Pins and flowers have certain powers to cause certain responses in us, and we erroneously think of perceived yellowness as a property of the flower as opposed to a property of our mind.
The traditional way of dividing properties into the primary and the secondary owes much to the fact that the science of the time (the science of Newton and Galileo) was enormously successful in explaining natural phenomena in terms of the so-called primary properties but fumbled badly in attempts to say much about the so-called secondary qualities. Shapes and motions of objects figured heavily in the mathematical physics of the day and the properties discussed in physical theory seemed easy to define without reference to the capabilities of human perceptual systems. Colors and odors, on the other hand, were recalcitrant to these early mathematical descriptions of the natural world. In a move of intellectual sour grapes, it was concluded that what wasn’t understood well was probably not really there: it was all in our minds. Thus the form of realism that we are calling “scientific” realism is really a mixture of idealism and realism. Unlike the naïve realist, the scientific realist is not a realist about all of the properties we take ourselves to perceive, but only some of them. It is important to note that the contrast between the naïve and scientific forms of direct realism here have to do with the realism, not with the directness. Thus, indirect forms of realism admit of both naïve and scientific forms (Dancy 1985). We postpone further discussion of realism and idealism until later in this section.
Turning to the directness of direct realism, we may ask what arguments there are to favor direct realism over indirect realism. The main argument for direct realism has to do with its closeness to common sense. Without reflecting much on the situation this is just how the way things seem to work: I perceive the table in front of me without necessarily perceiving anything else first. Further and more sophisticated arguments for direct realism hinge on criticisms of alternatives: indirect realism, for instance, runs into problems or has unpalatable consequences. For example, indirect realism may be incompatible with our belief that we know anything about things external to our own minds. Indirect realism has been charged with leading to the (to some) reprehensible view that you can’t know if anything or anyone besides yourself exists. For further discussion of such topics, see the discussion of skepticism in section ## of chapter ##. Before delving deeper into these alleged problems with indirect realism, it will be helpful to say some more about what it is and what arguments favor it.
Perhaps the single most popular and powerful consideration supporting the view that the external world is perceived only indirectly arises when we reflect on the nature of perceptual error. Examples of error abound: I misperceive a carpet sample to be purple when it is really brown; I mistakenly see a stick in the water to be bent or broken when it is really straight; I see a patch of water ahead on the road that turns out to be only a mirage. Most significant is the possibility of flat-out hallucination: when drunk or drugged one might see a pink elephant. Readers with healthy life-styles may better relate to the massive perceptual deception involved in dreams: one may dream that there is a pink elephant in the room when there is no such thing. Now, from the point of view of the perceiver, there may be no difference in hallucinating that there is a coffee mug in front of you and having the accurate perception that there is a coffee mug in front to you. In both cases the contents of your mind are the same. What makes one accurate and the other hallucinatory is the state of the external world. In the accurate case, your perceptual state is caused by there actually being a coffee mug there. In the hallucinatory case there is no mug and your state of mind that tells you otherwise. Your percept is caused perhaps by LSD. Now come the crucial steps in the argument for indirectness. First, note that even in the hallucinatory case, its very compelling to say that you are aware of something. Further, since the hallucinatory case is indistinguishable by you from the accurate case, in both cases what you are aware of first and foremost is the very same thing. And since what is similar in the two cases is the state of your mind, not the external world: what you are aware of first and foremost is the state of your own mind. Thus, even in the case of so-called accurate perception, you are aware of external objects like the coffee mug only indirectly, you are first and foremost aware of a state of you own mind, a state that could obtain without there actually being a coffee mug there, as in the cases of dreaming and hallucinating. Indirect realism, then, offers a very powerful and intuitive explanation of the very possibility of perceptual error.
Another argument for an indirect theory hinges on the time-lag between the events we perceive and the events of our perceiving. This is most easy to see in the case of looking at stars. Stars are very far a way and light takes many years before it reaches our eyes on earth. In many cases, when you are looking up at a star, the light reaching your eye was first emitted by that star thousands of years ago. For all you know, the star exploded last year and no longer exists. But the light carrying the information about the explosion won’t be here for a very long time. You look up at the sky and see a single shining un-exploding star. But that star, the one whose
light is entering your eye, no longer exists, let us suppose. The argument from time-lag to indirectness goes something as follows. In the case of the star, it no longer exists, but you are nonetheless aware of something. Since there is no longer a star around for you to be aware of, what you must be aware of is something else, and what better candidate than a state of your own mind? The time-lag argument, if it works at all, works equally well for objects not so distant: even the light bouncing off the furniture across the room takes some time to reach your eye. And even after it hits your eye, there is still a time-lag between that event and the occurrence of your state of perceptual awareness: the light must be processed by neurons in your retina, information is relayed from the retina through the optic nerve and on to various other parts of your brain until the moment of awareness that there is a chair in front of you. But you are aware right now. The distal stimulus was an event that happened in the past. So what you are aware of right now is something closer to you than the distal stimulus. What, then, is it that you are aware of? Again, the indirect theorist asks: what better candidate than a state of your own mind (and/or brain)?
We might sum up these arguments for indirectness as follows. Whenever you perceive something you are in some mental state: a state of awareness. You are aware of something. If you were aware of nothing you would be unaware, unconscious. But you are not unaware or unconscious. Whatever state you are in when you perceive something, say when you perceive a mug to be blue, could be replicated under conditions in which the mug isn’t blue or there is no mug at all. The external object is uneccessary for you to be in that state: the mug may have ceased to exist prior to the onset of that state as per the time-lag argument, or never existed at all as per the hallucination argument. Thus, what you are aware of is whatever it is that is necessary for you to be in that mental state. The external object is unnecessary. The internal state is necessary. Thus, what you are aware of is a state internal to you, a state of your own mind. The only way in which you are aware of thing external to your mind is indirectly.
Now that the arguments for indirect realism are in place, we can appreciate further considerations in favor of direct realism, since these considerations involve pointing out weaknesses in indirect theories and the arguments for indirectness.
Recall our discussion of homunculus fallacies from section ### Very simple versions of indirect theories themselves invite the charge of homuncular fallacy, for they attempt to explain the perception of external objects in terms of the perception of internal ones. Until the perception of internal objects is explained, the question of how perception works remains begged.
A more powerful and important criticism that might be made involves the indirect theorists’ explanation of error. In brief, the criticism is that while the indirect theorist has a nice explanation of error, the crucial components of the explanation can be had by even a direct theorist: the postulation of indirectness goes beyond what is needed to explain error. To spell this out a bit more, consider the following. The crucial component of the indirect theorists’ explanation of error is that there is a mismatch between an internal state and the external world. When I misperceive a straight stick to be bent, there is a mental representation internal to me that represents the stick as being bent. But the stick external to me is actually straight, so there is a mismatch between appearance and reality, between my internal mental state and the external mind-independent world. Similarly for flat-out hallucination. When I hallucinate that there is a pink elephant in what in reality is an otherwise empty room, my internal state fails to match external reality. My internal state says that there is a pink elephant in the room, but in external reality, the room’s contents are neither pink nor an elephant. Now, the direct realist need not deny this kind extremely powerful explanation of perceptual error. What the direct realist denies is the part of the indirect realist’s argument that moves from the fact that error involves a mismatch to the claim that one is aware of is the perceptual representation itself. Recall that the indirect theorist argues from the premises
(i) you have to be aware of something even in the case of hallucination
and
(ii) in the case of hallucination that something cannot be an external thing, because there may very well be no external thing (you may be hallucinating that you are talking to a unicorn even though there are no unicorns)
to the conclusion that that the thing you are aware of (stated in the first premise) must be an internal thing. Another way of describing the argument is as a disjunctive syllogism: either you are aware of something internal or something external, there is nothing external to do the trick, so, what you are aware of is something internal. Now a typical way of finding fault with disjunctive syllogisms is by attempting to show that their disjunctive premise constitutes a false dichotomy. Thus, it is open for the direct theorist to say that even though there is no actual external thing for the hallucinator to be aware of, being aware of some actual internal thing is not the only option.
The way the direct theorist can explain perceptual error is largely the same way in which the indirect theorist does it. The explanation at hand is a representational explanation, and the direct theorist need not deny that both hallucinating and accurately perceiving the presence of a pink elephant involves having mental representations of a pink elephant. What the direct realist denies is that what one is aware of in either case is necessarily the representation itself. One way of being a direct realist would be to identify the objects of perceptual awareness with the representational contents involved. Thus, in the accurate case, one mentally represents there being a pink elephant in front of one, and there actually is a pink elephant. In the illusory or hallucinatory case one mentally represents there being a pink elephant in front of one but there is no pink elephant. In both cases the answer to the question “what are you aware of?” is the same as the question “what are you mentally representing?”: the presence of a pink elephant. Thus the objects of awareness are representational contents, and as discussed in previous chapters/sections ###, representational contents need not exist. That is, a representation a can be about something that doesn’t exist, as in the case of a representation of a unicorn. There is, to be sure, the unsolved mystery, already discussed in section ### of chapter one of how a physical thing like a brain state can come to be about, that is, have as a representational content something that doesn’t exist. But that doesn’t pose any special problem for direct realist: it’s as much a problem for the indirect theorist.
What implications does cognitive science have for the debate between indirect and direct realists? As already mentioned, one of the core insights of cognitive science is the representational theory of mind, that mental processes involve mental representations. In keeping with this insight, the most obvious way of thinking of the perceptual awareness of some thing is as involving the mental representation of that thing. So if I am aware of some thing x, I have a mental representation y that represents x. Along these lines then, the indirect theory that says I am aware of an external thing x only in virtue of being aware of an internal thing y would be spelled out in accordance with the representational theory of mind by saying that in order to be aware of thing x I must not only represent it with mental representation y, I must necessarily be aware of y, thus, there is some third item z represents y that is involved in my direct awareness of y. For the direct realist, however, there need only be x and y, z is superfluous. The conflict between the direct and indirect theorist may then be seen as at least partially amenable to empirical investigation. It is open to empirical investigations whether there is anything in the nervous system that seems up to the task of playing the roles of y and z (thus supporting indirect theories), or if y is the only thing to be found.
Regardless of whether direct or indirect theories are true of perception, the nature of this philosophical debate has a close tie to cognitive science. One of the key insights that emerges from the debate, especially in wrestling with the problem of error, is the insight that perception involves representation. Further topics discussed in this chapter concern the nature of perceptual representation, and the relation between representations and the external world.
The most global form of idealism says that nothing exists independently of our minds. Berkeley famously argued that to be is to be perceived. Idealism admits of more local forms as well, thus, one may be a realist about some objects and their properties and an idealist about others. The versions of idealism that figure in contemporary discussions most frequently are local.
Why would someone be an idealist? What arguments can be martialed in favor of idealism? One of the clearest modern idealist arguments is due to George Berkeley (1710, 1713). Of Berkeley’s arguments for idealism, the one that he regarded as central to his system, and the one that has come to be called his ‘master argument’ is the following. If one can “conceive it possible” that the objects one thinks about “may exist without the mind”, then “it is necessary that [one] conceive them existing unconceived of or unthought of, which is a manifest repugnancy” (Berkeley 1710, §23).
The kinds of considerations just mentioned lead to a kind of tautological form of idealism. It is tautological insofar as it has as its basis the fact that everything that we think about is thereby thought about. Who could deny that? Everything that exists is thought about. Thinking the thought expressed by the previous sentence makes it the case that everything that exists is thereby thought about. Are these remarks sufficient to establish anything interesting? The claim that such and such depends for its existence on mind seems like a pretty bold and interesting claim.
Slightly different considerations in favor of idealism arise when we consider more local versions. Of particular relevance to the theory of perception is the question of the nature of the colors that we perceive objects as having. One kind of consideration in favor of idealism with regards to color asserts that we cannot conceive of color-as-we see it existing unperceived.
The philosopher Gareth Evans argues that there is a theoretical difficulty in imagining them instantiated unperceived. According to Evans the closest that we can come to imagining sensory properties instantiated unperceived is by imagining their non-sensory causal ground unperceived.
Evans argues that it is quite difficult to see how an object "as we see it" can be the same as when we do not see it (ibid.: 272-274). Suppose that I am seeing an apple as red. How can it be red when no one is seeing it, when, say, it is locked in a dark cellar? Evans contends that this is inconceivable (ibid.: 274). Evans writes that "All it can amount to for something to be red is that it be such that, if looked at in the normal conditions, it will appear red" (ibid.: 272). Evans contrasts this view with one that tries "to make sense of the idea of a property of redness which is both an abiding property of the object, both perceived and unperceived, and yet 'exactly as we experience redness to be'" (ibid.). Evans objects against this latter view that "it would be quite obscure how a 'colour-as-we-see-it' can exist when we cannot see it, and how our experiences of colour would enable us to form a conception of such a state of affairs" (ibid.: 273).
One way to defend this latter view is by suggesting that the obscurity alleged by Evans arises due to a concealed ambiguity in sentences employing phrases like "as I see it". Once such phrases are properly disambiguated, it becomes quite clear how a color as we see it may be the same when it is not seen. Consider sentences employing phrases with the form "x as I am F-ing it". Consider the sentence
“The chair as I am standing next to it is the same as
when I am not standing next to it.”
There is a reading of this sentence whereby it is quite clearly contradictory. On such a reading the sentence expresses the claim that a chair stood next to is a chair not stood next to. This is contradictory on the supposition that a chair cannot be both stood next to and not stood next to at the same time. Suppose, then, that we were to read the following sentences along similar lines.
“The chair as I see it is the same as when I do not
see it.”
On such a reading, Evans would be correct that it is quite obscure how the chair as I see it can be the same as when I do not see it. There is a difference between the chair as I see it and the chair when it is not seen by me, namely, in the first case I am seeing it and in the second I am not. And on the supposition that the chair cannot be both seen and unseen at the same time, the sentence under consideration expresses a contradiction.
However, some sentences employing phrases with the form "x as I am F-ing it" may be read in different way than considered so far. The sentences in question are those in which the verb phrase describes a representational act. Consider a sentence like
“The chair as I am describing it is the same as when
I am not describing it.”
This sentence admits of a reading whereby it expresses a contradiction. On such a reading the above sentence is equivalent to “The chair described is not described.” But on the alternative reading—the representational reading—a chair can be as I describe it even when I am not describing it. Suppose that I am describing the chair as having been manufactured in Switzerland. I am uttering the sentence "This chair was manufactured in Switzerland". My describing the chair is just my uttering a sentence. The chairs' being as I describe it however, is not its being a chair in the proximity of someone uttering a sentence. The chair's being as I describe, in this case, is its having been manufactured in Switzerland. Clearly a chair may have been manufactured in Switzerland regardless of whether I am now describing it as such. With this last point in mind, then, we may read
“The chair as I am describing it is the same as when I am not describing it”
as noncontradictory on the grounds that a Swiss chair doesn't stop being Swiss when I stop talking. Thus, the sentence
“The chair as I am describing it is the same as when I am not describing it”
admits of a representational reading which reveals the sentence to be non-contradictory. Similarly, if we view color vision as a largely representational affair, “The chair as I see it is the same as when I am not seeing” does not express a contradiction. My visual system may be representing the chair as being red, and the chair may be red even when I am not seeing it as such, just as the chair may be Swiss even when I am not describing it as such.
This argument does not definitively settle matters, however. Representational realists about color perception are still engaged in battle with color idealists or subjectivists, as we describe in the next section.