We saw in the second entry of this series that predicates like “…is true” have the following linguistic function: applied to an expression that designates a sentence X, they render a new (pro)sentence (“X is true”) that expresses exactly the same as the first proposition. This has lead some philosophers (not a majority, really) to think that the reason why our natural languages have predicates like “…is true” is not to help us reveal something particularly ‘deep’ about the world or about our relation to it, but just to help us say things it would be more difficult, or simply impossible to say without that predicate (e.g., “all logical consequences of the Peano axioms are true”, o “what is written on the Phaistos disk is true”). Truth would not be, if deflationists are right, a metaphysical, nor even an epistemological notion, but a boring (?) ‘prosentence-forming operator’, an instrument to give more expressive flexibility to our language.
I imagine that at this moment the patience of many readers will have almost evaporated. “What happens with all the traditional philosophical problems associated to the idea of truth?”, they will be asking. Well, I’ll offer in this and the following entry a brief summary of the casualties in this deflationary war.
1. Does truth consist in correspondence with the facts?
One of the first casualties is the traditional idea of truth as ‘correspondence’ between a proposition (or an idea, belief, etc.) and “the world” or “the facts”. According to deflationism, “…corresponds to the facts”, or “…corresponds to the way things really are”, are just other ‘prosentence-forming operators’ with exactly the same function as the simpler “…is true” (or, even simpler, as the prosentence “yes” pronounced after a whole proposition in interrogative mode): saying “what is written on the Phaistos disk corresponds to the facts” gives exactly the same information as saying “what is written on the Phaistos disk is true”, which is the same information expressed by what is written on the (still untranslated) Phaistos disk, whatever this might be. In this sense, we can say that the ‘correspondence theory of truth’ is right, but trivially right, for it just asserts the following tautology: “a proposition X is true if and only if X corresponds to the facts”. This is correct, but it is also as uninformative as saying “a proposition X is true if and only if the right answer to the question ‘X?’ is ‘yes’”. So, the ‘correspondence’-theory of truth would be as trivial as the dull ‘yes’-theory of truth 1
This does not entail that deflationism is anti-realist. I insist, what the correspondentists say is right, the problem is that it is trivial, and hence, philosophically uninteresting: it does not give us any additional information about the world, or about the relation between the world and language or the mind, with respect to what ‘non-philosophical’ propositions say. We could say that to be a realist is just to accept that some things exist or that some propositions are true, which is the same as saying that some things really exist and some propositions are really true. But this is something we just already do when we accept any of the propositions we accept in our everyday or academic life; saying that we adopt a philosophically realist stance to those propositions does not add absolutely anything to what we already accept in a ‘pre-philosophical’ way.
2. Is truth the goal of inquiry?
Another prominent role that the notion of truth has played along the history of philosophy is in connection to the idea of knowledge, science and inquiry. After all, when we investigate in order to learn something, what we pursue is to get the true answers to our questions, and knowledge is classically defined as ‘justified true belief’. So, is not truth the goal of our inquiry? Deflationists accept this thesis, but, as in the case of the notion of ‘correspondence’, they reduce it to a trivial assertion: to say that science or inquiry pursuits truth is just to say that we want to investigate in ways that, for every proposition “X”, lead us accept that X if and only if X (i.e., if and only if “X” is true). That the notion of truth does not play a specially deep function if this can be easily seen if we consider a concrete proposition in the place of X; consider, for example, the sentence “the continents are subject to a horizontal movement of translation in the Earth’ crust”. To say that we pursue truth in geological research amounts just to claim that what we are trying to do in geology is (amongst many other things) to investigate whether the continents move horizontally or not, or to say it in a more prosaic but perhaps more illuminating way: we try to study the Earth in such a way that the conditional probability of our accepting that the continents move, if they do, is as high as possible, and the conditional probability of our rejecting that the continents move, if they do not, is also as high as possible. Talking about a single proposition (like Wegener’s thesis in our example) allows to express the goal of science in a way that does not need to mention the concept of truth; this concept is helpful only in order to generalise that to all propositions (or, at least, to those considered in an area of research), i.e., in order to talk about an indefinite set of propositions (like in our former example “all the logical consequences of true axioms are true”). I leave for another occasion a completely different problem, which is whether this statement of truth as the goal of inquiry provides any help at all in order to understand what ways of doing science are better or worse, for, the more you think about the idea that science consists in trying to conclude that X if and only if “X” is true (at least for a subset of relevant propositions X), the more you will be perplexed about the question whether science actually gets this or not (see some related comments here) 2
We shall close this series in the next entry, commenting on the application of deflationism to the other central concept in metaphysics: being, or reality, or existence.