Addressing a Reply to “An Argument Against the Identity Theory of Mind”

I recently received a reply from Dr. Joshua Rasmussen under my article, An Argument Against the Identity Theory of Mind:

“Looks interesting. I wondered why one couldn't perceive the contents of perception at different times. Like maybe when a tree image is a content of a visual perception (brain state B), I could later have a new perception to be aware of brain state B. Then all the brain states would still be perceptible in principle. I also wondered why you would need such an elaborate argument. Here is a simpler one: 

1. A blue image is sometimes the content of a perceptual experience. 

2. A blue image is never the content of a brain state. (Neuroscientists have never found blue images in brains.) 

3. Therefore, a perceptual experience is not a brain state.”

Thank you so much for your reply. To make things easier, I’ll split your comment into two parts and address both parts individually.

“Looks interesting. I wondered why one couldn't perceive the contents of perception at different times. Like maybe when a tree image is a content of a visual perception (brain state B), I could later have a new perception to be aware of brain state B. Then all the brain states would still be perceptible in principle.”

My concern with your proposed solution is that it faces the same dilemma that would arise if the perceptual states were simultaneous. Let me try to illustrate the issue:

If a perceptual state A was the “perception of a perceptual state, B,” and B was a perceptual state that had existed or occurred prior to perceptual state A, then A could have neither been the perceptum of B (since A hadn’t even existed yet to be the perceptum of perceptual state B), nor could A have been the perceptum of perceptual state A. For, if A was the perceptum of perceptual state A, then the Principle of Perceptual Self-Exclusion would have been violated. However, it immediately follows from this that perceptual state A would have been imperceptible—in principle—unless it was the perceptum of another perceptual state, C,—a perceptual state that was itself different from perceptual state A and perceptual state B. Now, it is clear that if perceptual state C was a perceptual state that was existing or occurring later than perceptual state A and perceptual state B, then C could have neither been the perceptum of A, nor the perceptum of B (the reason being that C hadn’t even existed yet to be the perceptum of either perceptual state A or perceptual state B), nor the perceptum of perceptual state C. For, if C was the perceptum of perceptual state C, then the Principle of Perceptual Self-Exclusion would have been violated. However, it immediately follows from this that perceptual state C would have been imperceptible—in principle—unless it was the perceptum of another perceptual state, D,—a perceptual state that was different from perceptual state A, perceptual state B, and perceptual state C. And so on, ad infinitum.

Every “new” perceptual state that we introduced to account for the earlier perceptual state would itself be imperceptible—in principle—unless we introduced another perceptual state to account for it; and that “new” perceptual state would itself be imperceptible—in principle—unless we introduced another perceptual state to account for it—and so on, ad infinitum. In short, no matter how many perceptual states we posit, we will always get stuck with a “imperceptible” remainder left unaccounted for.

“I also wondered why you would need such an elaborate argument. Here is a simpler one: 

1. A blue image is sometimes the content of a perceptual experience. 

2. A blue image is never the content of a brain state. (Neuroscientists have never found blue images in brains.) 

3. Therefore, a perceptual experience is not a brain state.”

Personally, I am very sympathetic to this argument. However, my concern is that the identity theorist can accuse it of committing the so-called “phenomenological fallacy.” Indeed, in his article, Materialism, J.J.C. Smart addresses a very similar argument to the one you bring up:

“But what about consciousness? Can we interpret the having of an after-image or of a painful sensation as something material, namely, a brain state or brain process? We seem to be immediately aware of pains and after-images, and we seem to be immediately aware of them as something different from a neurophysiological state or process. For example, the after-image may be green speckled with red, whereas the neurophysiologist looking into our brains would be unlikely to see something green speckled with red. However, if we object to materialism in this way we are victims of a confusion which U.T. Place has called “the phenomenological fallacy.” To say that an image or sense datum is green is not to say that the conscious experience of having the image or sense datum is green. It is to say that it is the sort of experience we have when in normal conditions we look at a green apple, form example. Apples and unripe bananas can be green, but not the experiences of seeing them. An image or a sense datum can be green in a derivative sense, but this need not cause any worry, because, on the view I am defending, images and sense data are not constituents of the world, though the processes of having an image or a sense datum are actual processes in the world. The experience of having a green sense datum is not itself green; it is a process occurring in grey matter. The world contains plumbers, but does not contain the average plumber; it also contains the having of a sense datum, but does not contain the sense datum.” (Smart, Materialism, 653)

Now, I think Smart would respond to your argument by saying that the Materialist is not identifying the brain state with the “blue image,” rather he is identifying the brain state with the “having of a blue image;” and since the “having of a blue image” is not identical to the “blue image,” Smart would conclude that the argument in question was an ignoratio elenchi. Another unrelated concern of mine is that the “blue image” being “had” by me seems, prima facie, to be something entirely private to myself, and is not something that other people can “have.” If this be the case, then the Materialist might respond to your argument by saying that it would be expected that neuroscientists have never found “blue images” in brains, since those images would be private to their owners and inaccessible to anyone else—such as the neuroscientists. 

The argument that I give in An Argument Against the Identity Theory of Mind is indeed long and elaborate (and—I must admit—tedious), but I think it is able to avoid accusations of begging the question or involving the phenomenological fallacy. Indeed, I try to exploit Smart’s insistence on the distinction between the “perceiving of X” or the “experiencing of X” and X itself. I try to provide as many independent arguments as I can to show the impossibility of identifying the two. Furthermore, if we accept the Principle of Perceptual Self-Exclusion and the Principle of Perceptual Non-Loopability (both of which I attempt to argue for a priori), and if we also accept the idea that all brain states are—in principle—perceptible, it immediately follows that not all perceptual states are identical to some brain states (On pain of violating the Principle of Perceptual Self-Exclusion and the Principle of Perceptual Non-Loopability); and this entails that the identity theory is false.