Josh writes,
I would be interested to see how you respond to the following dilemma (from Peter Geach, "Truth and God," Proceedings of the Aristotelian Society, [1982]: 84).
Say proposition P1 is true because it corresponds to fact F. Does the proposition "Proposition P1 is true" (call it proposition P2) have a truthmaker? It seems that it should. Not only that, it seems that the truthmaker of P2 should be the same as P1 (i.e. F). But it's not obvious how F could make P2 true, since it is not obvious that F shares P2's "propositional" or "language-like structure," as you put it.
You've already said that some propositions do not have truthmakers, so perhaps you could just deny that P2 has a truthmaker. Or perhaps there is a way that F could do the job of truthmaking with respect to P2? Or perhaps P2 could be analyzed in a way that shows it is not really different from P1?
Thanks for your high-quality blogging!
You're very welcome! Interesting puzzle. It seems obvious that P2 has a truthmaker and that it has the same truthmaker as P1. Note also that if P1 is contingent, then P2 will also be contingent. For example,
Tom is sad
and
'Tom is sad' is true
are both contingently true and have the same truthmaker, namely, the contingent fact of
Tom's being sad.
And the same holds for all further iterations such as
"'Tom is sad' is true" is true.
Iteration of the truth predicate preserves the modal status of the base proposition. The regress here is infinite but benign. Whatever makes the base proposition true makes true every member of the infinite series of truth predications.
Now the problem you raise is that, while there is a clear isomorphism between 'Tom is sad' and Tom's being sad, there is not the same isomorphism between "'Tom is sad' is true" and Tom's being sad. The predicate in P2 is the predicate 'true', not the predicate 'sad.' P1 is about a man and says of him that he is sad; P2 is about a proposition and says of it that it is true. You are making an assumption, perhaps this:
A. If two or more propositions have the same truthmaker, then they must predicate the same properties of the same subjects.
The truthmaker theorist, however, is not committed to (A). The singular 'Tom is sad' and the existentially general 'Someone is sad' have the same truthmaker, namely, Tom's being sad, but the two propositions differ in logical form, and the second is not about what the first is about. The singular proposition is about Tom while the general proposition is not.
My point, then, is that the puzzle arises only if we assume (A). But (A) is no part of truthmaker theory. Truthmaking is not a 1-1 correspondence. 'Someone is sad' has many different truthmakers, and Tom's being sad makes true many different propositions, indeed, infinitely many.
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