Thursday, 22 December 2016

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)

4 comments:

Paul Herman said...

Have you seen Daniel Khaneman's reconstructions of precognitive vision? What is received by the retina before being decoded by the brain? I agree with Reid that perception & reason are equally reliable, & would, therefore, consider them both mere human constructs incapable of understanding the ding an sich. If, indeed, there is such a thing as the thing in itself. And you?

Jim Hamlyn said...

Thanks Paul,

I have Kahneman's "Thinking Fast and Slow" but i don't recall any vision reconstructions, sounds a little odd to me to try to reconstruct the unconstructed.

I'm afraid that I find a lot of perceptual science to be wildly confused. The experimental findings are interesting but the theory is dreadful. As Richard Feynman once said: “I believe that a scientist looking at nonscientific problems is just as dumb as the next guy.”

Like Reid, I don't take perception to be a construct at all. How could that even work without being viciously circular? I think Kant was wrong, but it takes a lot or argument to show how. Wittgenstein helps a lot.

Paul Herman said...

Really? I don't see anything odd in attempting to reconstruct images as they are received by the retina, before being translated to an inner understanding of an assumed external reality.

Neither do I see anything circular, vicious or otherwise, in believing all sensation & subsequent reasoning as part of a reality constructed by the perceiving body.

We might consider the different understandings of an alleged external reality offered by the eighty or so types of eyes that belong to different animals in the world. A dog, even if it were as intelligent as a human, couldn't imagine the existence of colour, because of its lack of retinal rods. A monotone world shows a different understanding of reality, albeit a small difference when compared to the possibilities implied by potentially larger differences in all sensorial perceptions. With a slight difference that allowed us to see into the infrared range of light's spectrum, we could see in what we now think of as 'dark'. Whereas if we could see the ultraviolet end, we would see nothing at all, since air itself would become opaque.

By the same token we might consider the possibility of senses existing which we can't imagine because of our very lack of them, which would show us a reality different to that which we are able to perceive with those we do have.

But without going as far as that, we might consider something as simple as size. We know that the matter that makes up an atom is infinitesimal in comparison to the space the atom occupies. We appear to each other to be solid bodies but we know that, at an atomic level, we are made up of so much more space than matter, that if we were very small creatures, we could hardly distinguish the massing of atoms that a human is, from the less dense air that surrounds him.

An ear could never imagine the existence of an eye, & if it could, it couldn't conceive of what sight is even if sight were explained to it. We are accustomed to thinking, in our simplistic way, that our understanding of reality — external or internal — depends on our five limited & fallible senses. But, in fact, the minds which understand reality are made up of a million separate processes that couldn't imagine each other but which only make up a comprehensive understanding through the mind's conflation of them all, to produce understood reality.

I can see no reason to believe the mind's truth is objective. That its truth coincides with a truth outside of itself. Ergo: It is a construct.

I look forward to your rebuttal! Thanks Jim

Jim Hamlyn said...

"I don't see anything odd in attempting to reconstruct images as they are received by the retina, before being translated to an inner understanding of an assumed external reality."

What magical intelligence is "attempting" this alleged "reconstruction" and "translation"? And how does this inner intelligence come to know that its reconstructions and translations are accurate? By what standards of correctness and what units of measure does it conduct its operations? What raw materials does it have at its disposal to pull off such feats of reconstruction and what yardsticks, samples and examples? How did it learn to translate images into whatever it is that you suppose it translates the "images" received by the retina into? And for whom is it constructing this translation? You? Itself?

If that doesn't begin to expose the profound oddity of the current state of Cartesianism then I'm at a loss.

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