Abstract

Leibniz was an outstanding mathematician of the 17th century and one of the most original philosophers of European history. Against this background it is astonishing that the ideas of Leibniz concerning probability have to date not been appreciated by mathematicians and philosophers. In this article the most important work of Leibniz with respect to probability theory, his De incerti aestimatione , is analysed. Here Leibniz deals with the 'problem of points', the then famous problem as to how to divide justly the stake when two players have to break off a number of prearranged games. The correspondence between Fermat and Pascal about this problem is regarded as the birth of probability theory. Yet, Leibniz favoured another solution to both of these. We reconstruct the underlying normative ideas of Leibniz and of Fermat and Pascal and show that they are equally sound and justifiable