[FOM] The Lucas Penrose Thesis

Jack Woods wood0571 at tc.umn.edu
Mon Oct 2 21:33:27 EDT 2006

Eray Ozkural wrote:

> However, at any rate, we should be able to agree on that the
>meaning of a natural language term as ordinarily understood by us is
>nothing more than an aggregate of mental states (i.e. states of perception)
>that are in our memory.
>Thus, we can make the computer watch video tapes that tell the meaning
>of these word, and the computer will be able to associate the sensory
>data with the word, by using machine learning algorithms.
I'm not sure why we should agree with this. The picture of meaning 
espoused here is a wildly controversial one. It's been a wildly 
controversial one since it was first proposed by the British Empiricists 
in the 17th century. Part of the implausibility of the picture comes 
from the fact that finding an "aggregate of states of perception" which 
can uniquely specify the meaning of any natural language term is nigh 
impossible. Further, it would then seem as if it is possible (in fact, 
likely) that the meaning of a term like "rabbit" is different for me 
than it is for you (since we almost certainly possess different 
aggregates of perceptual states).
With respect to the notion of mathematical meaning, Kripke's exposition 
of the difficulties in specifying that we mean "plus" by "+" in "2+2=4" 
and not "quus" where "quus" is some function like:

 quus(x,y) = plus(x,y) unless x > 10^10^10 or y > 10^10^10, in which 
case quus(x,y) = 5

come to mind. It's hard to imagine an aggregate of states of perception 
could distinguish between "plus" and "quus". Note that I'm not saying 
(necessarily) that the picture of meaning you present is mistaken, but 
simply that it isn't obviously correct. Given the many problems that 
arise for it, perhaps the claim that we should all be able to agree to 
it is a mite bit hasty.

Jack Woods

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