NICHOLAS RESCHER'S COHERENCE THEORY OF TRUTH Diderik BATENS 1. A ca re fu l re a d e r o f Nich o la s Rescher's Hyp o th e tica l Reasoning mig h t have remarked th at the logical machinery presented in that book has a much wider range of application than the e xp licit discussion o f th e b o o k suggested. I n Th e Coherence Theory of Truth (1 this machinery is not o n ly ap- plied to a wid e r domain o f problems, b u t comes t o p la y a central role in a preeminently philosophical theory, a theory of truth. The label "coherence th e o ry o f tru th " ma y be somewhat misleading a t first sight. The ma in subject o f the book is a criterion and n o t a definition. (Rescher himself defends th e suitability of defining truth in correspondence terms.) Further- more, correspondence considerations a s w e l l a s pragmatic considerations a re also made use o f in Rescher's coherence theory. I shall first t ry to make roughly clear how these three components are interrelated. The problem is to decide, in a given situation, the truth status of some proposition. The starting point is data. Un like in a correspondence theory, these data are not taken as completely certain. They are not truths, but merely truth candidates. The coherence machinery is applied t o th e data, and o n ly as a result of this process does one get truths. Pragmatic consider- ations come up in the justification of the whole procedure. Not- withstanding the important role o f correspondence and prag- matic considerations, th e crite rio n is essentially coherentist in that (a) the data as such guarantee no truth at all, and may indeed be fla tly inconsistent, leading to truth o n ly after they have been processed by the coherence machinery, and (b) the pragmatic considerations are used only in support of the valid- ity of the whole procedure, and not in support o f particular truth-claims. ( Press,1 1973. ) N i c h o l a s R E S C H E R : T h e c o h e r e n c e t h e o r y o f t r u t h . O x f o r d , C l a r e n d o n 394 DIDERIK BATENS It goes without saying that the objection that "a set of false- hoods may be as coherent as a set of truths" is pointless with respect t o a th e o ry which, a s the one under consideration, starts fro m experiential data. Of course, one might repeat the objection in a more sophisticated way, and ask wh y the ap- plication of the coherence machinery to the data should lead to a set o f true propositions. This objection can be directed against th e specific coherence machinery presented i n t h e book under discussion, o r against a n y coherence machinery in general. I shall return to the first version o f the objection in the sequel, and briefly consider the second version here. The concept of ''truth" that the objector has in mind cannot be the coherence concept o f tru th itself; indeed, e ve ry reasonable criterion of truth would accord with his own truths for trivia l reasons. What the objector has in mind is probably the defini- tional concept of truth as correspondence with the facts. The objection has then to do with the fa llib ility of the coherentist criterion, and not o n ly wit h its fa llib ility wit h respect to its own different applications i n time, b u t wit h respect t o th e facts as well. Tarski's definition of truth is unexceptionable of course, not only for the trivia l reason that it can be read as a (stipulative) definition, b u t also because i t expresses with o u t a n y doubt exactly what we mean b y 'true'. But precisely because it is infallible, it is useless as a criterion o r even as a basis fo r a criterion. Indeed, a n y criterion o f truth will be either almost application-free (lead to an empty set of truths) o r fallible, and this not for a theoretical reason, but for the simple and contin- gent reason that our experiential means are as they are. Con- sequently, a ll one can require from a criterion of truth is that it lead to 'p is true o n ly if there is a rational warrant for 'p is true'. This rational warrant cannot be found in correspondence considerations f o r reasons mentioned before (protocol sen- tences are a myth). Nor can it be found immediately in pragma- tic considerations, for they lead at best to useful tools, and, as Karl Popper argued in his Logic of Scientific Discovery, tools cannot be true o r false. This suggests that a rational warrant has to depend at least to some extent on coherence considera- NICHOLAS RESCHER'S COHERENCE THEORY OF TRUTH 395 lions. O n e ca n argue against either th e re la tive imp o rt o f coherence considerations in a criterion of truth, or the specific coherence machinery that is suitable, but the applicability of coherence considerations in general mu st be acknowledged. Returning to the question of whether any coherence criterion will guarantee the truth of its results, the answer seems to be that it never will guarantee truth in an absolute sense, but that some such theory will account for a rational warrant for truth, if any theory at all will. Of course, it never will do so on its Own; without data it is completely worthless. And there surely is no a priori way to find out which specific coherence criterion is to be adopted, nor even to what extent coherentist consider- ations have to play a role. But given the kind of epistemic sub- jects we think ourselves to be, and given the incomplete relia- bility o f o u r techniques f o r gathering data, a tru th criterion without any coherence machinery can hardly be defended. The fact that there is fa llib ility, and the fact that there is rational warrant only, might suggest that we are dealing with a theory of acceptance rather than with a theory of truth. Wha t is meant here, however, is n o t a th e o ry o f acceptance lik e many o f those n o w extant, wh ich account o n ly f o r general hypotheses and predictions, including so called retrodictions. Most of these theories start comfortably from a set of unques- tioned "evidence." However, a criterion of truth has to account even fo r this "evidence," o r expressed more suitably, f o r the factual truths that are used as a basis for accepting predictions and general hypotheses. Supposed that we use 'theory of ac- ceptance' in the broader sense, what are the reasons wh y the coherence theory cannot be considered as such a theory ? As Rescher argues, the rational warrant "applies to the criterion at issue, and not (save obliquely) with the propositions to which that criterion addresses itself ..." (p. 16). Two other differences seem relevant here. If an acceptance theory has to be a useful explicatum f o r wh a t happens, e.g., i n th e actual h isto ry o f science, it seems that it has to allow, a t least under definite conditions (a) the acceptance of inconsistent theories, and (b) the acceptance at the same time of some theory and of falsi- fying instances o r even a falsifying lo we r le ve l (read less 396 DIDER1K BATENS general) hypothesis. Such points are stressed in recent wo rk by, e.g., Paul Feyerabend. Risto Hilpinen has (in another con- text) argued against this possibility in Rules o f Acceptance and Inductive Logic, but his arguments are certainly not con- clusive if one tolerates different kinds o f acceptance (wh ich seems realistic), and if one introduces a logic that allows the deduction of sound conclusions from such a kind of inconsistent propositions. Although th is lo g ic w i l l d iffe r f ro m Rescher's coherence logic, it follows analogous lines and is surely not more complicated. It would unfortunately go beyond the limits of this paper to go further regarding this point. Anyhow, a l- though an acceptance criterion might lead to the acceptance of " p a rtly" falsified, and even contradictory hypotheses, this would surely be completely unsound for a criterion of truth. An inconsistent set of propositions can never be called true with- out vast violence to the term. A last difference that I wa n t to mention here is that theories of acceptance differ from theo- ries of truth in their aims and in the status of their results. The conditions f o r accepting a proposition p seem to depend on what we want to use the accepted p for, and on the amount of risk we can permit in this respect. But if 'truth' is meant in a serious sense, one cannot allow that truth would depend on such factors, even if one allows (and has to allow) fa llib ility in his claims to truth.