 Logical theories of probability retain the classical interpretation’s idea that probabilities can be determined a priori by an examination of the space of possibilities. However, they generalize it in two important ways: the possibilities may be assigned unequal weights, and probabilities can be computed whatever the evidence may be, symmetrically balanced or not. Indeed, the logical interpretation, in its various guises, seeks to encapsulate in full generality the degree of support or confirmation that a piece of evidence \(e\) confers upon a given hypothesis \(h\), which we may write as \(c(h, e)\). In doing so, it can be regarded also as generalizing deductive logic and its notion of implication, to a complete theory of inference equipped with the notion of ‘degree of implication’ that relates \(e\) to \(h\). It is often called the theory of ‘inductive logic’, although this is a misnomer: there is no requirement that \(e\) be in any sense ‘inductive’ evidence for \(h\). ‘Non-deductive logic’ would be a better name, but this overlooks the fact that deductive logic’s relations of implication and incompatibility are also accommodated as extreme cases in which the confirmation function takes the values 1 and 0 respectively. In any case, it is significant that the logical interpretation provides a framework for induction.