Is William G. Lycan rational? I would say so. And yet, by his own admission, he does not apportion his (materialist) belief to the evidence. This is an interesting illustration of what I have suggested (with no particular originality) on various occasions, namely, that it is rational in some cases for agents like us to believe beyond the evidence. (Note the two qualifications: 'in some cases' and 'for agents like us.' If and only if we were disembodied theoretical spectators whose sole concern was to 'get things right,' then an ethics of belief premised upon austere Cliffordian evidentialism might well be mandatory. But we aren't and it isn't.)
Being a philosopher, of course I would like to think that my [materialist]stance is rational, held not just instinctively and scientistically and in the mainstream but because the arguments do indeed favor materialism over dualism. But I do not think that, though I used to. My position may be rational, broadly speaking, but not because the arguments favor it: Though the arguments for dualism do (indeed) fail, so do the arguments for materialism. And the standard objections to dualism are not very convincing; if one really manages to be a dualist in the first place, one should not be much impressed by them. My purpose in this paper is to hold my own feet to the fire and admit that I do not proportion my belief to the evidence.
In sum:
1. The arguments for dualism and the arguments for materialism both fail.
2. The standard objections to dualism are not very convincing.
3. It is rational to be a materialist.
In my opinion (1)-(3) is a consistent triad. If so, what does 'rational' mean? It cannot have the Cliffordian meaning according to which one apportions one's belief to the evidence. For that would require suspension of belief on the issues that divide dualists and materialists given the truth of (1) and (2). But Lycan does not suspend belief; he remains a committed materialist. He believes beyond the evidence in that he believes on insufficient evidence. The evidence is insufficient because it is counterbalanced by the evidence for the position he disbelieves. However we define 'insufficient evidence,' it seems clear that if the evidence for p and the evidence for ~p are equal, then the evidence for either is insufficient.
Lycan's is an interesting case because it doesn't display all of the Jamesian marks. The issue is live for Lycan and for the people here present, but is it forced and momentous? An issue is forced in the sense of William James if it is such that one's remaining theoretically agnostic about it is tantamount to deciding it in a particular way. James gives the example of a man who hesitates to get married. "It is as if a man should hesitate indefinitely to ask a certain woman to marry him because he was not perfectly sure that she would prove an angel after he brought her home. Would he not cut himself off from that particular angel-possibility as decisively as if he went and married someone else?" (Will to Believe, p. 26) The man who refuses to commit himself to marriage commits himself to bachelorhood nolens volens.
But surely dualism versus materialism is not a forced option in the Jamesian sense. For one thing, one might reject both in the manner of the idealist. The positions are not logical contradictories of each other but logical contraries: they can't both be true, but they can both be false. Second, it is not the case that a suspension of judgment is tantamount to an opting for one side. If you take no position on dualism versus materialism, how does that commit you to one side or the other? On the God question, if one takes no position on whether or not God exists, then it it strongly arguable that one is a practical atheist: the agnostic lives as if God does not exist. And similarly for the immortality of the soul: to take no position is to live as if the soul is mortal. Or at least this is plausibly arguable. But the dualist need not be a substance dualist, and if he is not a substance dualist, then it is very difficult to see how the dualism versus materialism option is forced. And even if the dualist is a substance dualist, one might be a substance dualist without being committed to the immortality of the soul or mind.
A momentous option is one in which "We are supposed to gain, even now, by our belief, and lose by our nonbelief a certain vital good." (WB, 26) But I think it would be a stretch to think that the rather technical and abstruse issues that divide materialists and dualists are momentous in James' sense.
All this notwithstanding, the Lycan quotation above illustrates how rationality needn't require apportioning one's belief to the evidence. Or will you argue that Lycan is irrational in remaining a materialist despite his newfound insight that the arguments for it are not compelling?