Friday, September 4, 2009

Further thoughts on mentalism

I spent part of the afternoon reading an article that Andrew Cullison recommended, Feldman's, "Foundational Beliefs and Empirical Possibilities". It's an interesting read, in part, because it gives me a better sense of Feldman's views about justification and experience. I've been arguing that the mentalist view about evidence (i.e., that two subjects will have the same evidence if these subjects are in the same non-factive mental states) is wrong on something like these grounds.

1. p is part of S's evidence only if p.
2. p is part of S's evidence if p is known to S non-inferentially.
3. p can be known to S non-inferentially even if p is a contingent proposition about the external world.

I don't want now to debate 1-3. I wanted to comment on something from FB and EP. Feldman thinks that an argument of Pryor's shows that it's a mistake to say that our basic beliefs have to be beliefs about the character of our present experience. Some foundational beliefs (i.e., non-inferentially justified beliefs) can be beliefs about the external world. Pryor's argument can be stated as follows:

The Cognitive Scientists’ Discovery Argument
1. If traditional foundationalism is true, then S knows that there is a
tree in front of him only if S believes that he is having a ‘‘treeish’’
experience.
2. Cognitive science could (in principle) show that S does not believe
that he is having a treeish experience without thereby showing that S
does not know that there is a tree in front of him.
3. S could know that there is a tree in front of him without believing
that he is having a treesish experience. (2)
4. So, traditional foundationalism is not true. (1), (3)

At first, I thought that we could run a similar sort of argument against any view that seeks to undercut my argument against mentalism by saying that our evidence will consist of propositions about, say, the character of one's present experience while conceding that one has non-inferentially justified beliefs about matters 'beyond' present experience. The view would say that our evidence might consist of propositions about having a treeish experience but the beliefs we form about trees do not depend either psychologically or epistemically upon beliefs about experience. Here it is:

The Cognitive Scientists’ Next Discovery Argument
1. If the kind of mentalist foundationalism I'm considering is correct, then S knows that there is a tree in front of him only on the basis of propositions about the present character of experience where that has to do about things appearing "treeish" rather than propositions about trees (or any other contingent proposition about the external world that could be false if, say, I had been a BIV undergoing an indistinguishable experience).
2. Cognitive science could (in principle) show that S does not believe
on this basis.
3. S could know that there is a tree in front of him without believing
on this basis. (2)
4. So, the kind of mentalist foundationalism I'm imagining is not true. (1), (3)

I like this argument, but there's an easier one isn't there? Forget cognitive science and imaginary discoveries. The contents of our experiences _are_ such that our experiences needn't be veridical if we were BIV's. Those contents are among the bits of evidence that go towards justifying our beliefs about the external world. So, unless evidence can consist of falsehoods, we have evidence that our BIV twins do not. So, mentalism is false. It now looks like mentalism either has to (i) deny that E entails T, as it were or (ii) say that our experiences would be veridical even if we were BIV's. Check? Mate?

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