Keynes introduces three different principles under the single title “the principle of indifference”. The first is Bernoulli's princple of non-sufficient reason.If there is no known reason for predicating of our subject one rather than another of several alternatives, then relatively to such knowledge the assertions of each of these alternatives have an equal probability. Thus equal probabilities must be assigned to each of several arguments, if there is an absence of positive ground for assigning unequal ones.

A picture agrees with reality or fails to agree; it is correct or incorrect, true or false. What does this agreement consist in, if not in the fact that what is evidence in these language games speaks for our proposition?. The purpose of this paper is to outline a constructivist account of the notion of sense and to indicate why such an account is to be preferred to that given by classical semantics.

The object of this paper is to show why recent research in the psychology of deductive and probabilistic reasoning does not have.