Thursday, November 20, 2008

A New Knowledge Argument

Some philosophers reject Jackson's Knowledge argument by claiming that Mary does not really learn a fact (what redness looks like) when she sees something red for the first time; she merely acquires a new ability (to recognize redness). But I think the argument is easily tweaked to pre-empt such responses. Consider:

1. It is a factual question whether you and I experience the same color sensations when looking at an object.
2. This question cannot be settled by any physical information (or scientific inquiry).
3. So there are non-physical facts.

This strikes me as a pretty strong argument. The only response I can immediately think of is the 'old fact new guise' response, which claims that the phenomenal fact mentioned in #1 is actually identical to some physical fact, albeit in a new (hence unrecognized) guise. But which physical fact is it? I find this claim very mysterious.

8 comments:

  1. It certainly seems to me that scientific inquiry can and eventually barrin extinction will settle the question of whether Mary and I perceive the same thing when we see red with at least the same level of confidence that it settles the question of whether my perception of "red" today is the same as that of "red" yesterday, reducing the question to te grue problem, which I think you consider to be closed.

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  2. Suppose it's a law that humans in neurological state N experience color sensation R. Then if you and I are both in N when looking at an object, we are both experiencing R. Obviously if we are both in N then that is a physical fact, and the law relating N to R is arguably a physical fact. So the conjunction of these two claims, which is arguably a physical fact, could settle the question of whether you and I both experience the same color sensation when looking at an object.

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  3. How is this really different from the original knowledge argument? If what's being compared in your premise 1 is items of knowledge about what the experience is like, then your argument doesn't get off the ground if there are no such items of knowledge, as the critics maintain. But if that's not what's being compared in your premise 1, it is far from clear what is being compared, if anything. And, of course, if we don't know what's being compared, it's pretty hard to evaluate 2, and if nothing's being compared, 1 is false (I take it that Vassar and Iacono's responses are pushing along these lines).

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  4. I'm with Leo. It is a neurological question whether you and I experience the same color sensations when looking at an object.

    The causation of these sensations is entirely physical. It's to do with the physics of light, how the rods and cones stimulate the optic nerve, how the ventral stream acts etc. Where we know for sure color perception is different - as in the case of color blindness - we know there are purely physical causes for this difference.

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  5. Even if (2) is true I don't think (3) follows. And I agree with others that (2) is problematic.

    Consider the problem of some physical fact that to know requires more physical facts than can be represented in a finite universe.

    I don't raise this to apply it directly to this situation obviously. Just to show that it is possible for there to be a physical truth that can't be proven by physical means.

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  6. Michael - that's not what the grue problem is. (I agree with your comparative claim. Intra-personal comparison is equally problematic for the physicalist: even supposing we could conclusive establish that my brain states yesterday were the same as today's, that wouldn't settle whether my qualia had changed without my realizing it. We can be pretty confident that the correlation remains; but not as certain as if the psycho-physical correlation were instead identity, as the physicalist proposes.)

    Leo - "the law relating N to R is arguably a physical fact"

    That sounds like Chalmers' psycho-physical bridging laws. I don't want to quibble over semantics here, but if we need an additional fundamental law that relates the physical stuff to the mental stuff, then that's not physicalism. Take physicalism to be the claim that once we have your N, then R comes along for free. (That's most obviously the case if N = R. You don't need extra laws to relate things to themselves.)

    Another way to show this is that no amount of third-personal physics could lead us to posit such a law. (An outside observer examining our world through Kripke's telescope wouldn't seem to have any reason to posit the existence of qualia at all.)

    Aaron - the point is to make it more intuitively obvious that there really is a matter of fact at stake here. I have nothing to say to die-hards who dispute premise (1); but I trust they are vanishingly few in number.

    Georges - It's not in dispute that qualia have physical causes. But note that effects are distinct from their causes, such that even if we've observed their 'constant conjunction' so far, it's always conceivable that they could diverge in future.

    Clark - Let's idealize. There's some sense in which even finitely unrepresentable physical facts are indeed settled by physical information and idealized scientific inquiry. So my claim is that the fact in premise (1) is even more problematic than that. No amount of idealization would help, because third-personal inquiry isn't even heading in the right direction.

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  7. The causation of these sensations is entirely physical. It's to do with the physics of light, how the rods and cones stimulate the optic nerve, how the ventral stream acts etc.

    I think Richard is pretty clearly right in his response to this, above. If [X] causes [Y], and [X] has quality [Q], you can't validly conclude that there's no non-[Q] component to [Y].


    Where we know for sure color perception is different - as in the case of color blindness - we know there are purely physical causes for this difference.

    Key phrase is "where we know..." Isn't it possible that what you experience when you look at a "red" apple is radically different from mine, but there simply wouldn't be anyone who would know about this disparity?

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  8. If we allow that some fact about qualia is unknowable, like whether or not you and I experience the same "blue", then does this imply that both it and its converse are ideally conceivable? I think it does.

    If it is unknowable whether or not you are experiencing qualia at all, then there is definitely no a priori contradiction in conceiving that you are not. (If it was contradictory a priori, then it couldn't be unknowable.)

    If we take the truth of skeptical claims involving other minds to be unknowable, then the zombie argument should directly follow from that.

    It seems like if you make this case, most of the standard physicalist responses would be preempted. Physicalists don't have any special arguments against skepticism. Just like the rest of us they assume that other minds exist and use that assumption to create a theory of mind. But our ultimate inability to 'know' that skepticism is false is identical to our ability to 'conceive' that it is true.

    And if it is empirically knowable whether or not a person is having an identical qualia to me when they are in a relevantly similar brain state, I'd like someone to outline how this can be. I'm not really a philosopher, I'm a neuroscience graduate student, and I happen to know that the term "qualia" has no meaning whatsoever in neuroscience. If a quale is defined in first person terms a priori, and it has identical primary and secondary intensions, then neuroscience can never associate it with third person phenomenon... that seems pretty obvious. Qualia can't even be a part of neuroscience, much less reducible to it.

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