Sunday, May 19, 2013

Evolutionary Argument Against Naturalism (p. 5)

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Evolutionary Argument Against Naturalism
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The evolutionary argument against naturalism goes like this:
  1. Pr(R|N&E) is low
  2. The person who belives N&E (naturalism and evolution) and sees that Pr(R|N&E) is low has a defeater for R.
  3. Anyone who has a defeater for R has a defeater for pretty much any other belief she has, including (if she believed it) N&E.
  4. Therefore, the devotee of N&E (at least such a devotee who is aware of the truth of premise 1) has a self-defeating belief.
One of the big reasons to accept the Probability Thesis (premise 1) is that if N&E were true, then the semantic content of our beliefs is causally irrelevant in the sense that a belief causes stuff by virtue of its neurophysiological (NP) properties, and not by its semantic content. If a belief had the same NP properties but different content, the same behavior would result (the same neurophysiological properties means we would have the same electrical impulses travelling down the same neural pathways and thus issuing the same muscular contractions). Even if that weren’t the case, the ANPD scenario suggests it’s still possible for “garbage” beliefs to be associated with electrochemical reactions producing advantageous behavior. If semantic epiphenomenalism (SE) isn’t true on N&E, then semantic pseudo-epiphenomenalism (SPE) is, and both Pr(R|N&E&SE) and Pr(R|N&E&SPE) are low, thereby making Pr(R|N&E) low.

The argument for the Defeater Thesis (premise 2) is that if R is defeated in (S1), then it is defeated in (S2), and if R defeated in (S3), then it is defeated in (S4), and so forth, where (S6) is the scenario of a person who accepts both N&E and the Probability Thesis. The general idea is that the effect of an evolutionary naturalist believing Pr(R|N&E) to be low is akin to believing that drug XX has been put into one’s body (where drug XX destroys the cognitive reliability of most who take it).

The upshot of all this is that there is a serious conflict between science and naturalism, because the conjunction of naturalism and evolution is in an interesting way self-defeating.

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