Sunday, November 20, 2005

Considering how we know (cont'd) ...

Bill Peschel attached a very interesting comment to my previous post, noting that "in dealing with the outside world, there needs to be some way for the brain to translate the signals it receives into a 'language' it can understand, so the inability of the cochlear and the nerve impulses to vibrate at the exact frequency of the noise doesn't prove bothersome," adding that he'll "be interested in seeing where [Russell Brain is] going with this line of thought."
Actually, I should have pointed out what the first chapter of Mind, Perception and Science has to do with, which Brain explains at the outset:

Epistemology seems to me to be the cardinal problem of modern thought, for we cannot separate our conclusions concerning the nature of perceiving from our conclusions as to the nature of what we perceive. As a neurologist I shall be chiefly concerned with the causal aspects of pereception. I make no apology for that, for it is much neglected by philosophers, who mostly concentrate upon perception as presentational immediacy. No theory of perception can be adequate which does not fully account for both.

He then goes on to examine, first, physiological idealism and then the varieties of critical realism, adding that "I find both ... equally unsatisfactory."
My previous post quoted from the section on physiological idealism.

In his comment on my post, Bill mentioned "the triangulation developed by the noise level from the two ears, as well as the subtle change in noise one ear receives when the head rotates slightly," and Brain also points out that "in our awareness of our own bodies we are directly aware of a three-dimensional object. The position of this object can be changed in relation to the external world and the position of its parts can be modified in relation to the body as a whole. Thus the body serves as a primary model of three-dimensional space."

Brain cites two main objections to physiological idealism. The first involves applying the idealism to the idealist himself: "... if all sense-data are states of his brain, this must also be true of the sense-data derived from his own body; and his brain itself, if, as is not impossible, he could see it in a mirror in the course of an operation, must be reduced to an activity of itself." He may insist that the sense-data provide information about things existing independently of his awareness of them, but, as Brian points out, it's hard to see how he can arrive at this conclusion if the sense-data are "nothing but states of his own brain."

The second objection is that "if physiological idealism is true we might expect to find that there is something circular about the events in the cerebral cortex, for it is these, we are told, which are 'projected' on to the outside world when we perceive a circle." But "nothing of the sort is true."

As it happens, "when we perceive a two-dimensional circle we do so by means of an activity in the brain which is halved, reduplicated, transposed, inverted, distorted, and three-dimensional. ... the circle which is said to be projected from the cerebral cortex never existed there at all."

So here is the mystery, thus far: The nature of the stimulus as transmitted differs entirely from the nature of the stimulus as received. Yet any number of people receiving the same stimulus will perceive the same thing. Our agreement regarding the terminus a quo is grounded in our shared experience of the terminus ad quem. So , one might ask, is reality a consensus?

Next: What Brain says about critical realism.

By the way, the idea behind this series of posts is that by taking a close look at a couple of interesting, related books by the same author, blogger and readers can together try to arrive at the sort of understanding one would hope to find in a really thorough review. That is the experiment I referred in the previous post.

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