Materialism and the Problem of Truth
II. The Argument from Truth
A second argument I provided was the argument from truth. Let us reflect for a moment on truth as an epistemic summum bonum or supreme good. It seems to me that the scientific enterprise, at least as classically understood, is based on a desire first and foremost to know the truth, and only secondly to manipulate and control the world. We are told, for example, that no matter how comforting it is to have religious beliefs, if those beliefs are not based on good evidence that they are true, then they ought to be abandoned.
But this raises some questions about what this property of truth is, that we should abandon beliefs that we may find comforting for the sake of truth. Here it seems that many “deflationary” accounts of truth are going to fail to capture why we care about truth so much. In William Hasker’s generally friendly response to me in Philosophia Christi he asks
And now consider truth: why should the naturalist find it problematic? That snow is white is true just in case snow is white; what would motivate (let alone force) a naturalist to reject this?
Here Hasker is adverting to a Tarskian disquotational theory of truth; truth is a matter of taking quotation marks of sentences. But truth has to have more to it than this if it is to carry the weight of being the supreme epistemic value. Timothy Erdel takes Quine to task for, at one point, saying that he rejected religion and politics in favor of the pursuit of truth, but then he defines truth in this disquotational way. As he says:
If truth is no more than Quine generally claims when he is describing or explaining truth (as opposed to when he is appealing to it as the grounding motive more his life’s work), namely, the removing of quotation marks from the names of sentences, then one senses some fairly significant equivocation in his use of the term, “truth.”
Presumably one does not cast aside all claims from religion and politics to pursue philosophy as a vocation solely to facilitate the removing of quotes from names of sentences…
So to make the sort of thing we ought epistemically to pursue, even at personal cost, truth must be something more than mere disquotation. But what can it be? I think that only the correspondence theory is the only one that adequately underwrites the intuition that many of us share that truth is the supreme epistemic good.
There is a problem with truth as correspondence, however, from a broadly materialist point of view. If truth is a relationship between someone’s belief that something is so and the reality that it is so, then what that means “there is at least one reptile” would not have been a truth during the Jurassic period, unless there was someone in existence during the Jurassic period who had confidence that his or her thought corresponded to the truth “there is at least one reptile.” And unless there is something like a God, we do not know of anything alive during that time that had confidence in the representation, “There is at least one reptile alive now.”
Because of this, the advocate of a broadly materialist world view may be inclined to accept the idea what can be true false are not states of the person but propositions. These propositions could exist timelessly, but not exist in anyone’s mind. If that were the case then the proposition “There is at least one reptile alive during the Jurassic period” would be a truth that would exist at that time, because it would be true at all times.
This account of propositions is hard to square with some versions of naturalism, according to which everything that exists at some place and time in particular. However, if we waive this requirement, there are still difficulties. The argument from reason based on mental causation maintains that naturalism cannot explain how one thought can cause another thought in virtue of its content. On this view, how would it be possible for our thought to be related to the truth that our thoughts are about, if our thoughts are completely products of the spatio-temporal-physical world, but the truth of our thought does not exist in any particular place or time. The physical, is supposed to be causally closed according to broadly materialist world-views, and as such nothing outside the physical, whether eternal propositions, or nonphysical souls, can affect what goes on in the physical world. Because of this, I regard this move to non-spatial propositions as the acceptance of a poisoned pawn, the taking of which will make the next argument, the argument from mental causation, impossible to answer.