Laplace Pierre Simon de (1749–1827), French mathematician and astronomer who produced the definitive formulation of the classical theory of probability. He taught at various schools in Paris, including the École Militaire; one of his students was Napoleon, to whom he dedicated his work on probability.
According to Laplace, probabilities arise from our ignorance. The world is deterministic, so the probability of a possible event depends on our limited information about it rather than on the causal forces that determine whether it shall occur. Our chief means of calculating probabilities is the principle of insufficient reason, or the principle of indifference. It says that if there is no reason to believe that one of n mutually exclusive and jointly exhaustive possible cases will obtain rather than some other, so that the cases are equally possible, then the probability of each case is 1/n. In addition, the probability of a possible event equivalent to a disjunction of cases is the number of cases favorable to the event divided by the total number of cases. For instance, the probability that the top card of a well-shuffled deck is a diamond is 13/52.Laplace’s chief work on probability is Théorie analytique des probabilités (Analytic Theory of Probabilities, 1812).
See also PROBABILIT. P.We.