Confirmation Theory

Confirmation theory is the study of the logic by which scientific hypotheses may be confirmed or disconfirmed (or supported or refuted) by evidence. A specific theory of confirmation is a proposal for such a logic. Presumably the epistemic evaluation of scientific hypotheses should largely depend on their empirical content — on what they say the evidentially accessible parts of the world are like, and on the extent to which they turn out to be right about that. Thus, all theories of confirmation rely on measures of how well various alternative hypotheses account for the evidence. Most contemporary confirmation theories employ probability functions to provide such a measure. They measure how well the evidence fits what the hypothesis says about the world in terms of how likely it is that the evidence would occur if the hypothesis were true. Such hypothesis-based probabilities of evidence claims are called likelihoods. Clearly, when the evidence is more likely according to one hypothesis than according to an alternative, that should redound to the credit of the former hypothesis and the discredit of the later. But various theories of confirmation diverge on precisely how this credit is to be measured. A natural approach is to also employ a probabilistic measure to directly represent the degree to which the hypothesis is confirmed or disconfirmed on the evidence. The idea is to rate the degree to which a hypothesis is confirmed on a scale from 0 to 1, where tautologies are always assigned maximal confirmation (degree 1), and where the degree of confirmation of the disjunction of mutually incompatible hypotheses sum to the degrees of confirmation of each taken separately. This way of rating confirmation just recapitulates the standard axioms