In Frank Jackson's famous argument, Mary has grown up without ever seeing anything red or reddish, but she has learned complete and correct scientific accounts of the world, including of optical and perceptual phenomena. One day, Mary sees a red tomato. In so doing, she finds out something: she finds out what it was like for other people who were seeing red all along. But she knew all the science of subjective experience, but without seeing red (or having an apparent memory of seeing red?) she couldn't know this, so there must be a scientifically inaccessible component to subjective experience that she learned.
I think the argument may well fail. Start with an argument that even before she sees a tomato, Mary could have known what it is like for other people to see red, simply by having enough naturalistically accessible information about her future. For she could know that at t1 she would see a tomato, that a tomato is red, and that there is a common core to people's experiences of red. Thus, she could know that:
- Other people's experiences of red are like that experience.
Now, you might object: But that's not what it is to know what it is like to see red. But this isn't clear. Suppose she is now seeing a tomato. Then what does she know? What she knows is simply:
- Other people's experiences of red are like this experience.
But observe that there is reason to think that (1) and (2) express the same proposition. When the sunset is present, I would say I know:
- This is a sunset
- That was a sunset.
If this is right, we have good reason to think (1) and (2) express the same proposition. But perhaps you dispute this (I am not sure of it myself). Maybe the different ways that a present-tense "this" and a non-present-tense "that" point give rise to different proposition. If so, then it may very well be the case that before she sees the tomato, Mary cannot know (2). But a this/that difference does not challenge materialism. After all, we all think materialism holds about the moon. But by exactly the same token as (1) and (2) express different propositions, so do:
- That is the crater Clavius
- This is the crater Clavius
Now, it could be that Mary's gain in knowledge is in some way deeper than that of the astronomer who is put blindfolded in Clavius. But that needs an argument. On its face, Mary has simply gained a new way to refer to her experience of red: beforehand, she would call it "that future experience", and when faced with it, she would call it "this present experience". And that does not seem enough to ground an argument against materialism, dearly as I love arguments against materialism.