Lewis G. Creary

The dissertation is a detailed critique of the main elements of Hans Reichenbach's pragmatic treatment of the problem of induction. In the introductory Chapter I we give a broad overview of Reichenbach's theory of probability and induction, indicating that he approaches the problem of justifying inductive inference in general by attempting first to reduce all kinds of non-deductive reasoning to combinations of inferences in accordance with the rules of deductive logic together with RRI -- the "rule of induction." Having thus reduced inductive inference to its elementary components, he then proposes to solve the problem of justification by providing independent pragmatic justifications for those components. In Chapter II we show that Reichenbach's analysis of inductive inference involves a second non-deductive elementary component, a rule of application (RRA), which he fails to integrate properly into his theory of induction. RRI is a rule for "inferring" statistical probability statements from observed relative frequencies -- a rule of inverse inference. RRA is a rule for "predicting" individual events on the basis of statistical probability statements -- a rule of direct inference. We show that Reichenbach construes elementary inductive "inference" in such a way that only a pragmatic justification of the _combined_ use of RRI and RRA will suffice for a Reichenbachian solution to the problem of induction. It is further argued that there is no reasonable pragmatic point of view from which RRI alone could be justified. In Chapter III we find that RRA, when suitably modified to avoid a certain defect in Reichenbach's version of it, can justifiably be used by an agent only if he has (a) knowledge of a certain probability, (b) knowledge that he is going to deal with almost all of the members of a certain sequence, and (c) knowledge about the sizes of the utility stakes associated with the sequence in question. Reichenbach makes no provision for (c), while his attempt to satisfy the requirement (b) by appeal to Poisson sequences turns out to be fundamentally unsatisfactory. The knowledge required by (a) is presumably to be supplied through the use of RRI. In Chapter IV we consider the combination of RRI and RRA, which yields a rule for "predicting" individual events on the basis of observed relative frequencies -- i.e., a rule of predictive inference. The task of justifying such predictive inference is the heart of the problem of induction as it arises for Reichenbach. Yet we argue that RRI does not yield the probability knowledge required for the statistically justified use of RRA, while an alternative approach to the justification of predictive inference suggested by Reichenbach's reply to an old objection of Paul Hertz is shown to require a conception of predictive inference which is pragmatically unacceptable. Reichenbachian predictive inference thus remains unjustified. In Chapter V we consider in detail Reichenbach's "method of correction," which lies at the foundation of both his theory of higher-level probabilities and his attempted epistemological reduction of all scientific inference to a combination of deductive logic with his elementary inductive rule(s). His justificatory arguments in this connection concerning earliness of probability-finding are found to be grossly unsatisfactory, while the prospects for an alternative statistical justification are shown to be nil. Thus, the method of correction and the reductive developments which depend on it appear to be quite groundless. In Chapter VI, we draw the earlier results together and conclude that Reichenbach's attempt to provide pragmatic foundations for an empiricist theory of knowledge falls far short of its goal in ways which have not generally been recognized. Finally, we offer some brief reflections on the pragmatic rationale which underlies the Reichenbachian program.