The Achievement of Illusion

Akiyoshi Kitaoka

There’s an interesting discussion on the New York Review of Books at the moment between writer Tim Parks and realist philosopher Riccardo Manzotti on the subject of consciousness. Manzotti rejects the idea, popular in much cognitive neuroscience, that our experience of the world is a mediated product of the mind or brain. Instead Manzotti takes an “externalist” stance that conceives of experience as somehow “spread” out across the things of the world. Even if we agree with Manzotti’s realism, this needn’t commit us to either internalism or externalism. Experiences simply happen wherever they happen. A walk in the highlands certainly doesn’t happen in your head, but it makes little sense to say that it is spread over the mountains either.

One of the standard objections to realist accounts of consciousness is what is known as “the argument from illusion”. The basic idea is this. If we are susceptible to optical illusions and other illusory phenomena, then we cannot rely on perception. Manzotti responds:

“Mirages and Hallucinations are not necessarily ‘pure appearances’, one sees something that is really there, only that one takes to be something else. Yet it is not misperception, rather it is misjudgement!”

Few people would claim that mirages, hallucinations and illusions are not caused. But if one mistakes a reflection in a mirror for an actual thing, then it isn’t true that “one sees something that is really there”. If the mirror (the thing that is really there) isn’t seen and its reflection “is taken for something else”, then quite clearly the mirror has been misperceived. Such a response cannot be a “misjudgement” because judgement is not a precursor to perception. If you look before you leap, you don’t judge before you look.

Manzotti seems to have fallen into a conceptual trap. In his eagerness to refute internalism, he has adopted an opposing view when it would have made more sense to stick to his otherwise justified critique of internalism and to point out that consciousness is something we ascribe to whole people, not to their brains or minds.

Parks and Manzotti discuss an interesting optical illusion by Akiyoshi Kitaoka. What appear to be blue and green portions are in fact the same colour. Internalists argue that this illusion shows that everything we perceive is an illusion generated by the mind/brain. If so, this would be a truly miraculous achievement on the part of the brain even if it were sometimes wrong. However, a far simpler and more parsimonious explanation is that these apparent colours are merely the result of the very opposite of an achievement. They are the product of a very ordinary perceptual failure brought about by the circumstances in which the illusion is presented. Change the circumstances in the right ways and it becomes obvious that there is only one colour involved. No neural mysteries need be imputed.

The effect conforms the same principle used to make colour prints with inkjet printers or to produce colours on the screen you are currently using. In fact, the same basic principle enables us to place tiny black and white squares together to produce a patch that looks grey.

If it weren’t for the fact that all normally sighted people are susceptible to illusions in the same sorts of ways and in the same sorts of circumstances, then all illusionistic media (images, movies, representational paintings and drawings etc.) would be unacceptable as representations. There would simply be no ways and no circumstances in which such representations would be like the things they might otherwise represent.

Sometimes things can look like other things because they are genuinely alike. Two leaves from the same tree will usually be alike in a whole variety of respects. Such isomorphism is the very basis of what we take to be observer-independence, of what is objectively real. On the other hand, things can look like other things because in some regularly occurring or contrivable circumstances it can be difficult for us to discriminate between them in one or more respects. Equally, and for the same reasons, two things that are actually the same in one or more respects can seem to be different. The mastery of illusion is not an achievement of the brain, it is an achievement of human culture.

I will leave the last word to the Scottish realist philosopher Thomas Reid:

“The sceptic asks me, Why do you believe the existence of the external object which you perceive? This belief, sir, is none of my manufacture; it came from the mint of Nature; it bears her image and superscription; and, if it is not right, the fault is not mine: I even took it upon trust, and without suspicion. Reason, says the sceptic, is the only judge of truth, and you ought to throw off every opinion and every belief that is not grounded on reason. Why, sir, should I believe the faculty of reason more than that of perception?—they came both out of the same shop, and were made by the same artist; and if he puts one piece of false ware into my hands, what should hinder him from putting another?” (Thomas Reid, IHM 6.20, 168–169)

Masters of Illusion

A Cartesian can believe that the existing world is not visible, that the only light is that of the mind, and that all vision takes place in God. A painter cannot grant that our openness to the world is illusory or indirect, that what we see is not the world itself, or that the mind has to do only with its thoughts or with another mind. (Maurice Merleau-Ponty 1964, 186)

The following discussion aims to show that our perception of the world is in no way illusory. Whilst we are obviously susceptible to illusions, our various skills and tools enable us to recognise and exploit many of these susceptibilities in a variety of powerful ways.

According to Alex Byrne: "Perception comprises, by stipulation, veridical perception and illusion" (2009). For Byrne, and many other philosophers, one “veridically perceives an object if and only if one sees it, and it is the way it appears or looks.” In other words, veridical perception is what we usually mean when we speak of perception in ordinary language. It is the perception of how objects ordinarily are, or what we typically call “ordinary perception”, “normal perception” or just plain “perception”. However, like Byrne, some philosophers claim that perception “comprises”, or at least sometimes involves, illusion or illusory perceptions. Two important points need to be made regarding this claim. Firstly, an illusory parrot is not a species of parrot—in fact it is not a parrot at all. And by the same token, an illusory perception is not a perception either, at least not in the respects in which it is illusory. The same is true of misperceptions, false perceptions or perceptual mistakes etc. A failure to perceive something in certain respects cannot be a sort of perception in those respects. Missing a train is not an instance of catching a train.

Secondly, to notice or recognise an illusion is not to be at its mercy. It is to grasp the illusion for what it is. To say that one length of an optical illusion "looks" shorter than the other is not to say that the line is shorter than the other. Recognising that the two lines could be mistaken as being of different lengths does not preclude our seeing that they are the same length.

In a forthcoming book chapter, John O’Dea writes: "I can think of no good reason to deny that a tilted coin could be seen as elliptical and flat with respect to the viewer. This would be tantamount to denying the possibility of illusion." It is perfectly justified to say that a tilted circular coin can be treated, regarded or considered as a flatly presented ellipse, because a tilted circular coin can be successfully depicted as a flatly presented ellipse. However, if O’Dea intends “seen” in the sense of “perceived”, which seems likely in the context of his discussion, then his claim should be examined in light of the conclusions we have already drawn about the relation between perception and illusion. Thus, if the alleged perception is an illusion, then it is not a de facto perception in the relevant respects. On the other hand, if looking at a tilted circular coin results in a perception of an illusion—in seeing the illusion for what it is—then a description of the illusion alone will not answer the question of what has been perceived. What has been perceived is a tilted circular coin that can be successfully depicted through the use of a flatly presented ellipse. 

In the concluding paragraph of the chapter, O’Dea writes:

Constancy often fails; deep shadows can make surface colour perceptually unclear; at severe angles, shapes constancy disappears; size becomes harder to judge from more distant objects; and so on. Is perceptual experience illusory in these conditions?

Evidently O’Dea has mistaken illusions of inconstancy for actual failures of constancy. Constancy is usually characterised as the stability we regularly encounter in the properties of perceived objects, despite changes in angle of view, illumination, shading etc. So if circumstances of apparent inconstancy do not constitute actual inconstancy, but rather the illusion of inconstancy, then it would be false to conclude that they are perceived as inconstant. A failure to see that a dead parrot is deceased is not a failure of constancy on the part of the parrot.

If the properties of a stable object, like a book or a table (or even a dead parrot), are perceived as having constancy, there is nothing to prevent us from also regarding, considering or treating these same objects as if they have inconstant features like being blurred when viewed at close quarters or being small when seen from a distance or being colourless in moonlight etc. This is important because it shows that we are often capable of treating things in two quite different ways, one of which involves the capacity to represent the actual properties we perceive whilst the other involves a more sophisticated knowledge of how to represent objects by way of illusionistic representational techniques.

The following passage from Maurice Merleau-Ponty makes a related point:

It took centuries of painting before the reflections upon the eye were seen, without which the painting remains lifeless and blind, as in the paintings by primitive peoples. The reflection is not seen for itself, since it was able to go unnoticed for so long, and yet it has its function in perception, since its mere absence is enough to remove the life and the expression from objects and from faces. [...] It is not itself seen, but makes the rest be seen. Reflections and lighting in photography are often poorly portrayed because they are transformed into things..." (2012, §364)

It is true that eyes quickly lose their lustre in the absence of lubrication, but if the reflection is not seen for itself, an obvious question arises. Is the reflection on a pond seen for itself, or the reflection in a mirror? Merleau-Ponty provides no obvious answer, but it seems reasonable to conclude that his view would be this. Until the discovery of depictive techniques capable of transforming reflections into things, people were not capable of representing them. In other words, it is by virtue of the emergence of pictorial techniques that visual phenomena like blurring, reflections, perspectival distortions etc. have become communicable (there is even evidence that this applies to the colour blue). This is not to say that reflections have not always played a part in perception. After all, if tears produced no reflections, they would be invisible. As Merleau Ponty says: the reflection “is not itself seen” but it enables the tears, the pond etc. to “be seen”. And what of mirrors? Do we not perceive the reflection in a mirror? His point is that the reflection is not perceived “for itself” as a thing. We might occasionally mistake a reflection for a thing, but this would not constitute a perception. It would be the perceptual equivalent of sitting on the platform of Glasgow Queen Street station dreaming that you are on the 8:15 to Edinburgh Waverly.

Schwitzgebel (2011) raises another reason to be wary about the claim that perception involves illusion. 

Consider the oar's looking bent in water. Could we say that the oar's appearance is an illusion? That seems natural. But if so, then presumably the look of things through a glass of water, which will be similarly distorted, is also an illusion. And if that, then also the look of things through a magnifying glass held appropriately close? Through a telescope? Through ordinary corrective lenses? (166n.8)

It makes little sense to say, for example, that when things recede into the distance, they gradually become illusory. They are simply harder to make out. When we look across a table, we see less of the far side. This isn't an illusion. It's a commonplace and unremarkable consequence of the spatial fall-off of sensory input. The more distant an object, the less we see of it. The effect is regular and gradual and leads eventually to the complete loss of input as objects recede into the distance. If our sensory systems were perfect, there would be no fall-off. But then again, if our sensory systems were perfect, there would be nothing we could not perceive and there would be no such thing as partially seeing or barely hearing something etc. Partial perception and the gradual failure to make things out in certain respects are just normal characteristics of our sensory relation to the world.

In ordinary circumstances, when we perceive things normally, we often describe them as if they have properties that they do not actually possess. We might say that shiny surfaces commonly "look silvery or wet", that rainclouds "look leaden or grey" or that fast-moving objects "appear to be blurred". These are not perceptual reports (or at least not perceptual success reports), but they do not preclude other (arguably more objective) ways of reporting things in terms of their actual perceived properties. In normal usage though, it doesn't really matter which strategy of representation we invoke in describing the objects we see (or "seem to see" on account of the ordinary fallibilities of all sensory systems), because we all familiar with the same representational techniques and we are all subject to very much the same perceptual strengths and weaknesses.

Very much less theoretical attention has been paid to those perceptual failures that are the logical corollary of success. […] In the wake of each positive perceptual advance the reciprocal logic of discrimination failure opens up new prospects for influential representational substitution. (Brook 1997)

This is a vitally important observation with profound implications. To be under the spell of an illusion is to be incapable either of recognising it or exploiting it. It is simply to make a mistake. However, to recognise an illusion is not only to be capable of recognising and perhaps avoiding other similar illusions. It is to have an insight into how other similar illusions might be staged and used as effects. While many creatures are capable of learning from their mistakes, only tool-users are capable of recognising and exploiting their mistakes in the form of illusionistic effects.