I listened to the first lecture in David Chalmers’ Locke Lectures currently taking place at Oxford and I was intrigued by the argument he gave in defense of the claim that we can have a priori knowledge and do conceptual analysis even if we cannot give definitions of the concepts that we are analyzing. The argument appealed to the claim that any counter-example to a definition involved reasoning about possible cases and so we could give an account of the a priori in terms of our capacity to think about possible scenarios and our judgments about whether certain sentences are true in those scenarios.
So to put it overly simply one can say to Quine “sure, my concept may change and if so this wouldn’t be true but given that my concepts don’t change we can see that this would be the case.” So to take pain as an example. When we are reasoning a priori about what we would say about pain (can there be pain/pleasure inversion for instance) we can admit that if we change what we mean by pain this or that will be different. But as long as our concept of pain doesn’t change we can say this or that would be true in this or that scenario and therefore bypass the entire Quinian argument altogether. This would seem to give Dave a response to the type-q materialist who has been getting so much attention over at Philosophy Sucks! lately. This is because they seem to be saying that since our concept of pain might change we cannot know a priori whether zombies are conscious or not. Dave responds by saying that as long as we do not have to change our concept of pain we can see that zombies are not conscious. I think that this response to the Quinian argument is quite good but I would respond to it differently.
To fill this in with a particular example that I have talked about before let us focus on the notion of pain and Pain Asymbolia. Now many philosophers hold that it is a priori that if something is a pain then it will be painful (and that conversely if something is painful then it will be a pain). Now suppose that one of these philosophers finds out about pain asymbolia and denies that these people are in pain. Now suppose that this person comes to change their mind and instead thinks that they are in pain but that pain and painfulness are (contrary to appearances) only contingently related. What are we to say? In the paper Dave says,
A ﬁfth issue is the worry that subjects might change their mind about a possible case without a change of meaning. Here, one can respond by requiring, as above, that the speciﬁcations of a scenario are rich enough that judgments about the scenario are determined by its speciﬁcation and by ideal reasoning. If so, then if the subject is given such a speciﬁcation and is reasoning ideally throughout, then there will not be room for them to change their mind in this way. Changes of mind about a fully speciﬁed scenario will always involve either a failure of ideal reasoning or a change in meaning.
I can agree with this in principle but since I can clearly conceive pain and painfulness being only contingently related it cannot be the case that we are in a position to determine which concept of pain is the one which will be employed in ideal reasoning. We may have our favorite but there are arguments on both sides and it is not clear where the truth lies. So though we can know a priori that either pain is necessarily painful or that it is contingently painful but we cannot know which is true now. To know that we would have to settle the pain asymbolia case; but that case it hotly contested (pun sadly intended )