Wednesday, May 23, 2012

[PHI 1000] One's modus ponens is another's modus tollens

Based on his thought experiment about Mary the neuroscientist, Frank Jackson argues roughly as follows: 
  1. All information is physical information only if Mary, who has all the physical information concerning human color vision before her release, does not learn something new about color upon her release.
  2. Mary does learn something new about color upon her release.
  3. Therefore, not all information is physical information.

 To this argument, Daniel Dennett has replied by arguing roughly as follows:
  1. If Mary, who has all the physical information concerning human color vision before her release, does not learn something new about color upon her release, then all information is physical information.
  2. Mary does not learn something new about color upon her release.
  3. Therefore, all information is physical information.
Both arguments are valid. Which do you find more convincing?  

3 comments:

  1. Dennett. The idea of complete knowledge of the physical facts about colour perception really is so alien to our normal state of affairs that I honestly think we shouldn't trust our intuitions about what it would be like.

    On a side note, I'm trying to formalise the arguments to fit the Modus Ponens/ Modus Tolens quote. It's trickier than it first looks.

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    Replies
    1. As far as not trusting our intuitions goes, I could not agree more. By the same token, one could argue that the idea of something non-physical is just as foreign to us as the idea of complete knowledge of the physical facts about color perception, and hence that our intuitions about what that thing might be like are probably unreliable.

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    2. I guess one challenge could be to ask what it means to appeal to intuitions. Maybe the argument is that this notion of what an intuition is, is too limited to capture the role that intuitions play. For instance there's an implicit assumption in this argument that intuitions themselves are guided by our experiences. Isn't something like intuition supposed to help us resolve some of the problems an over-reliance on experience can cause in for instance our philosophy of language? It can hardly both act as a backstop to experience while at the same time being constrained by it can it?

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