What? Where? When? Why? pp 69-100 | Cite as

# Invention and Appraisal

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## Abstract

Among the many important contributions made by Wesley Salmon to the explication of the logic of hypothesis-appraisal has been his insistence that considerations additional to the inductive relations between evidence-statements and hypothesis may bear upon the probability of the latter. In particular, he has urged that the *prior* (to test) probability of a hypothesis *H*, as well as the *likelihoods* of *H* and not-#, must be taken into account in assessing the *posterior* (to test) probability value of *H*. Salmon has argued that the relationships among these several probability-values are captured by a particular interpretation of Bayes’ Theorem — a theorem of the formal probability calculus (Salmon [1967a], [1970c]). If this proposal is adopted, the problem arises of how to assign a value to the prior probability of *H*. Since no frequencies directly relevant to *H* will be available prior to initial testing, Salmon, who adopts a frequency interpretation of probability, must appeal to *other* considerations in estimating this prior probability value ([1967a], pp. 124 ff). These are what he calls “plausibility considerations” for *H*. As well as formal and pragmatic criteria, they include material criteria, such as considerations of simplicity and symmetry. From plausibility considerations of these various types, a scientist would be enabled to judge the *plausibility* of his/her hypothesis prior to test, and to estimate a *prior probability* value for insertion in Salmon’s Bayesian schema (ibid., pp. 115 ff, and my pp. 76–8 below). Even if, in many cases, the prior probability of a hypothesis is difficult to quantify precisely, Salmon’s recognition that this factor plays an important role in the appraisal of the hypothesis has always seemed to me to be a valuable insight.

## Keywords

Prior Probability Inference Rule Inductive Inference Plausible Hypothesis Receive View## Preview

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