Thursday, May 1, 2014

Truth by convention

I stipulate that "It xyzzies" is true. Clearly I have failed to make "It xyzzies" meaningful. My stipulation is compatible with "It xyzzies" meaning that 2+2=4, but also with its meaning that everything is round or non-round. So stipulating a sentence to be true isn't going to be sufficient to introduce the sentence into our language. But if I say anything more about the meaning of the sentence, I risk that no true sentence might fit what I say, and we lose the point of truth by convention. Nor does it at all help to stipulate a family of sentences at once, e.g., stipulating that whenever S and T are true, so is "S*T", and when "S*T" is true, S is true, and when "S*T" is true, T is true. That still fails to introduce a connective "*", unless we say more about the meaning. The stipulation I gave is compatible with too many things. For instance, "S*T" could mean "God believes S and God believes T", or it could mean "(S or S) and (T and T)". And if I say more about which one I mean, I risk the stipulating being unsuccessful. So that's that for truth by convention. It's fun to drive nails in the coffins of dead theories.


Heath White said...

It might not be *quite* this easy.

At least part of the meaninglessness of this stipulation is that (either) (i) we have no idea what the inferential potential of the sentence is, and/or (ii) the sentence has no compositionality.

Probably the fans of "truth by convention" thought of the stipulations as applying to words, not whole sentences. Though I suppose you could ask them why they thought that.

Alexander R Pruss said...

Let's add: You can infer the sentence from any other sentence, and you can infer any tautology from it. :-)

It's true that the sentence is compositionally basic, though it can be composed into other sentences, like "It xyzzies and the sky is green." But we can also do the same thing with a predicate: stipulate that Xyzzies(x) is always true. :-)