A Definition of "Degree of Confirmation"

1. The problem. The concept of confirmation of an hypothesis by empirical evidence is of fundamental importance in the methodology of empirical science. For, first of all, a sentence cannot even be considered as expressing an empirical hypothesis at all unless it is theoretically capable of confirmation or disconfirmation, i.e. unless the kind of evidence can be characterized whose occurrence would confirm, or disconfirm, the sentence in question. And secondly, the acceptance or rejection of a sentence which does represent an empirical hypothesis is determined, in scientific procedure, by the degree to which it is confirmed by relevant evidence. The preceding remarks, however, are meant only as accounts of methodological tendencies and are not intended to imply the existence of clear-cut criteria by means of which the scientist can decide whether-or, in quantitative terms, to what degree-a given hypothesis is confirmed by certain data. For indeed, no general and objective criteria of this kind are at present available; in other words, no general definition of the concept of confirmation has been developed so far. This is a remarkable fact in view of the importance of the concept concerned, and the question naturally suggests itself whether it is at all possible to set up adequate general criteria of confirmation, or whether it may not rather be necessary to leave the decision in matters of confirmation to the intuitive appraisal of the scientist. This latter alternative would be highly unsatisfactory; for firstly, it would clearly jeopardize the objectivity-in the sense of intersubjectivity-of scientific procedure. Secondly, it would run counter to a view of confirmation which is now widely accepted; according to this view, statements about confirmation assert nothing regarding an observer's subjective appraisal of the soundness of a hypothesis; rather, they concern a certain objective relation between a hypothesis and the empirical evidence with which it is confronted; this relation depends exclusively on the content of the hypothesis and of the evidence, and it is of a purely logical character in the sense that once a hypothesis and a description of certain observational findings are given, no further empirical investigation is needed to determine whether, or to what degree, the evidence confirms the hypothesis; the decision is a matter exclusively of certain logical criteria which form the subject matter of a formal discipline which might be called inductive logic. Of course, the widespread acceptance of this view does not prove that it is sound and that the program implicit in it can acttually be carried out. The best-and perhaps the only-method of settling the issue seems to consist in actually constructing an explicit and general definition and theory of confirmation. To do this is the purpose of this article. It is intended to present in outline, and with emphasis on the general methodological issues, a theory of