| Phi 346-02 Spring 2014 |
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David Chalmers (1966-) is the first person we’ve discussed who is not only alive but still only middle-aged. His work centers on issues in the philosophy of mind, so his focus in thinking of meaning is on the content of our thoughts.
In the wake of Kripke’s examples of statements, like ‘Hesperus is Phosphorus’ that were necessary even though a posteriori, a number of people pointed to a sense in which the content of our thought is not exclusively internal to us. One well-known argument for this is due to Hilary Putnam (1926–) and employs an example that Chalmers will often refer to.
We shall suppose that somewhere there is a planet we shall call Twin Earth. Twin Earth is very much like Earth: in fact, people on Twin Earth even speak English. In fact, apart from the differences we shall specify in our science-fiction examples, the reader may suppose that Twin Earth is exactly like Earth. He may even suppose that he has a Doppelganger—an identical copy—on Twin Earth, if he wishes….
Although some of the people on Twin Earth … speak English, there are, not surprisingly, a few tiny differences between the dialects of English spoken on Twin Earth and standard English.
One of the peculiarities of Twin Earth is that the liquid called “water” is not H2O but a different liquid whose chemical formula is very long and complicated. I shall abbreviate this chemical formula simply as XYZ. I shall suppose that XYZ is indistinguishable from water at normal temperatures and pressures. Also, I shall suppose that the oceans and lakes and seas of Twin Earth contain XYZ and not water, that it rains XYZ on Twin Earth and not water, etc.
Hilary Putnam, “Meaning and Reference,” The Journal of Philosophy, vol. 70 (1973), pp. 699-711 (on JSTOR at 2025079)
He goes on to note that Earthlings visiting Twin Earth would report back, “On Twin Earth the word ‘water’ means XYZ,” and argues that this means that meanings are not “in the head” (since what is in the head would not have differed from Earth to Twin Earth before the chemical composition of the stuff called ‘water’ was discovered and there is no reason to suppose the meaning of ‘water’ has changed since then). Putnam’s distinction between what is “in the head” and what is in the environment is what Chalmers has in mind when he speaks of “intrinsic” and “extrinsic” properties (and “Twin Oscar” is supposed to be the identical copy of an Earthling “Oscar”).
Chalmers also alludes to another example from the same paper, where Putnam says,
Suppose you are like me and cannot tell an elm from a beech tree.… My concept of an elm tree is exactly the same as my concept of a beech tree (I blush to confess).
Ibid., p. 704.
but goes on to insist that nevertheless refers to different trees when he uses the two words.
My comments on this part of Chalmers’ article concern his §3. His attempts to capture the sense of content that is “in the head” have a connection to Kaplan: you can think of Chalmers’ “scenarios” as comparable to the “inner stories” in Kaplan’s §IX—though Chalmers doesn’t discuss quantifying-in. They are even closer to Kripke’s idea of “qualitatively identical situations” and the idea of “semantically neutral” vocabulary (p. 50) is intended to limit consideration to vocabulary that is “qualitative,” and the range of information he labels “PQTI” is intended to be limited in similar ways. (Chalmers also uses a little logical notation, some of which you seen; but, as a reminder, ‘~’ means ‘not’ and ‘≡’ means ‘if and only if’.)