Friday, July 03, 2009

More on Merricks on Truthmaking

I've now finishing my re-reading of Trenton Merricks' book Truth and Ontology and I'm still quite unconvinced by his contention that what's true does not depend on what exists in any substantive way. A couple posts ago I noted my main reasons for dissatisfaction with Merricks' arguments:
  1. He loads down truthmaker principles, which affirm a substantive dependence of truth on being, with extraneous commitments.
Most significantly, he takes the raison d'etre of such principles to be that of catching all sorts of metaphysical "cheaters"--those who either (a) try to have their truths on the cheap, without paying an appropriate metaphysical price, or (b) invoke "suspicious" properties to do their truthmaking work. I deny that these concerns are fundamental to truthmaker principles. Such principles are merely attempts to articulate the driving intuition behind correspondence theories of truth, namely, that truth depends on being in a substantive way and, therefore, that there must be some being corresponding to any given truth that "makes" that truth true. What properties count as "suspicious" is to be determined not by truthmaker principles but by explanatory considerations (e.g., Are such properties merely "ad hoc", or do we have independent reasons for positing them? Can they plausibly be regarded as primitives, or can they be cashed out in some explanatorily informative way?)
  1. He never carefully defines the crucial notion of "aboutness" upon which his major arguments depend.
Merricks insists that truths can only be made true by what those truths are "about". He then argues that for many types of truths there are no existing things that those truths are "about", from which he concludes that truthmaker principles are false. It is clear that the notion of "aboutness" is crucial to this argumentative strategy, and it is surprising that a philosopher of Merricks' calibre doesn't define it carefully. In fact, he explicitly declines to give an analysis (pp. 33-34) and relies, instead, on a handful of examples (e.g., pp. 28-29) which indicate only that "aboutness" has something to do with relevance. Here's one such example:
[Y]our thumb fails to be a genuine truthmaker for FLT [Fermat's Last Theorem]. . . . Even though your thumb's existence necessitates FLT's truth, FLT is not about your thumb. (p. 27)
I'll grant that a thumb is not a truthmaker for FLT. And I'll grant that a thumb's inadequacy as a truthmaker for FLT can be explained, to a first approximation, by the observation that FLT is not relevantly "about" a thumb. But Merricks needs to go a lot further than that. If he wants to refute truthmaker principles (and he does) then he needs to give an analysis of what the relevant "aboutness" relation is. Were he to provide such an analysis, of course, fans of truthmaker principles could subject it to scrutiny. Leaving the notion nebulous allows Merricks to rest his argument on impressionistic declarations that this or that type of truth isn't relevantly "about" any existing thing. He thus arrives at his conclusions by a certain amount of theft over honest toil.

In the rest of this post I'm going to help Merricks out a bit by clarifying the relevant sense in which truthmakers must be what truths are "about".

First, we need to distinguish between connotative and denotative senses of "about". In the connotative sense, to speak "about" (say) FLT is to say something about the content of the theorem. This requires some understanding of what the theorem means. But I can say, "I heard that some dude proved FLT a few years ago" and thereby talk "about" FLT without having any clue what FLT stands for. That's a strictly denotative sense of "about". Now, truthmaker principles are metaphysical, not epistemological in nature. They require that there exists something in virtue of which a truth is true, but they don't require us to know what that something is. Hence, the relevant sense of "aboutness" is denotative, not connotative.

Second, truthmakers must relevantly necessitate their truths. What that means is not simply that it must be impossible that the truthmaker exist and the truth in question fail to be true. Your thumb, after all, necessitates FLT in that sense. No, it must also be the case that the truth in question could be derived from knowledge of the truthmaker. In other words, if (hypothetically) someone were fully acquainted with a putative truthmaker and only that truthmaker, would that person thereby know with certainty that the truth in question is true? Your thumb is not a truthmaker for FLT because someone acquainted only with your thumb (however fully) would not thereby know FLT.

I claim that the above two points are all there is to the relevant "aboutness" relation. A truth is "about" one of its truthmakers in the relevant sense if and only if (a) there exists something such that (b) full acquaintance with that thing and only that thing would enable one to know with certainty that the truth in question is true.

Merricks, undoubtedly would want to insist on further constraints, at which we could have a healthy debate about them. My complaint is that he should have gone at least as far as I have here, and he could easily have done so.

In my next post, I'm going to use my "aboutness" criterion and show that on metaphysical assumptions that Merricks accepts, there are truthmakers for all of the truths for which he says there aren't any.


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