 If there are formula_1 events under consideration, the probability of each occurring is formula_2

In philosophy it corresponds to a concept that allows one to assign equal probabilities to outcomes when they are judged to be equipossible or to be "equally likely" in some sense.The best-known formulation of the rule is Laplace's principle of indifference (or "principle of insufficient reason"), which states that, when "we have no other information than" that exactly formula_3 mutually exclusive events can occur, we are justified in assigning each the probability formula_4 This subjective assignment of probabilities is especially justified for situations such as rolling dice and lotteries since these experiments carry a symmetry structure, and one's state of knowledge must clearly be invariant under this symmetry.A similar argument could lead to the seemingly absurd conclusion that the sun is as likely to rise as to not rise tomorrow morning.