Monday, June 8, 2009

Can the appearance of a phenomenal-physical gap be explained away?

In the remaining posts of this series I address a question that I think is not addressed frequently enough in the literature. Why do people suppose that there is an epistemic gap? Asked in the context of discussions of Mary, the relevant question to ask is: Why do people suppose that prerelease Mary is phenomenally ignorant?

It is no answer to such a question to say that it is intuitive that prerelease Mary doesn’t know what it’s like to see red. For the next question to raise is: Why is that intuitive? And it is no answer to that question to credit the intuition as being true. The truth of an intuition can’t suffice to explain its intuitiveness. Further, if the above arguments concerning Swamp Mary are sound, the intuition in question is false. I think that in general, if an intuition retains its intuitive pull despite being shown to be false, it helps to have an explanation of the source of the intuitive pull. It is toward such an explanation that the current section is directed.

The intuition under question is a thesis that I will, following an earlier work (P. Mandik, in press),  call the Experience Requirement, “the thesis that, for some experiences at least, and red experiences in particular, knowledge of what it’s like to have such an experience requires that the knower has had or is currently having such an experience.”

In an earlier time, classical empiricism was the grounds for a defense of the Experience Requirement. We see expressions of something very close to the Experience Requirement in the work of Locke and Hume. Here’s Locke from An Essay Concerning Human Understanding : “…we see nobody gets the relish of a pineapple, till he goes to the Indies, where it is, and tastes it.” Here’s Hume from An Enquiry Concerning Human Understanding: “A blind man can form no notion of colours; a deaf man of sounds. ….A Laplander or Negro has no notion of the relish of wine.” Locke and Hume offer the Experience Requirement as a piece of common sense that is supposed to help build their case for their theory of ideas. The thought seems to be that their empiricistic theory of ideas is supported by how well it is able to explain the Experience Requirement: if ideas are made of sensory impressions or copies thereof, then of course “a blind man can form no notion of colour.” 

I have serious doubts about whether the account whereby concepts are composed of sensory impressions or copies thereof will stand up to neuroscientific scrutiny. Though I think Weiskopf (2007) makes a convincing case against the neurophysiological plausibility of this kind of concept empiricism, I will not recount the case or pursue this line further here. Instead, I present considerations that directly target the Experience Requirement. 

One way of formulating a question about the truth of the Experience Requirement is as follows. Is it possible that the informational channels that put normally sighted persons in contact with redness are more capacious than either any other sensory input channels or the human memory systems that constitute our objective conceptual grasp of our inner and outer worlds? When we look to scientific estimates concerning, for example, the bandwidth of human color vision, we find the basis for the following two lines of thought. The first is that we can explain why people may have found the Experience Requirement plausible. The second is that considerations concerning neural bandwidth and storage do not suffice to ground the Experience Requirement’s truth. I develop these lines of thought further in the next post of the series.