Justification, or at least ‘justification’, bulks large in recent epistemology. The view that knowledge consists of true-justified-belief has been prominent in this century, and the justification of belief has attracted considerable attention in its own right. But it is usually not at all clear just what an epistemologist means by ‘justified’, just what concept the term is used to express. An enormous amount of energy has gone into the attempt to specify conditions under which beliefs of one or another sort (...) are justified; but relatively little has been done to explain what it is for a belief to be justified, what that is for which conditions are being sought. The most common procedure has been to proceed on the basis of a number of obvious cases of justified belief, without pausing to determine what property it is of which these cases are instances. Now even if there were some single determinate concept that all these theoriests have implicitly in mind, this procedure would be less than wholly satisfactory. For in the absence of an explicit account of the concept being applied, we lack the most fundamental basis for deciding between supposed intuitions and for evaluating proposed conditions of justification. And in any event, as philosophers we do not seek merely to speak the truth, but also to gain an explicit, reflective understanding of the matters with which we deal. We want to know not only when our beliefs are justified, but also what it is to enjoy that status. True, not every fundamental concept can be explicated, but we shall find that much can be done with this one. (shrink)

Among the various meanings in which the word ‘probability’ is used in everyday language, in the discussion of scientists, and in the theories of probability, there are especially two which must be clearly distinguished. We shall use for them the terms ‘probability1’ and ‘probability2'. Probability1 is a logical concept, a certain logical relation between two sentences ; it is the same as the concept of degree of confirmation. I shall write briefly “c” for “degree of confirmation,” and “c” for “the (...) degree of confirmation of the hypothesis h on the evidence e“; the evidence is usually a report on the results of our observations. On the other hand, probability2 is an empirical concept; it is the relative frequency in the long run of one property with respect to another. The controversy between the so-called logical conception of probability, as represented e.g. by Keynes, and Jeffreys, and others, and the frequency conception, maintained e.g. by v. Mises and Reichenbach, seems to me futile. These two theories deal with two different probability concepts which are both of great importance for science. Therefore, the theories are not incompatible, but rather supplement each other. (shrink)