Archaeologists have found evidence of people playing games of chance from the earliest human societies, and such games have been popular throughout history and across cultures. So it is perhaps surprising then that the mathematics of probability was not worked out until the seventeenth century.

The foundations of probability theory were established in a correspondence between the French mathematicians Blaise Pascal and Pierre de Fermat. They exchanged five letters during the summer of 1654 in which they discussed two problems which had previously been considered by the Italian mathematician Cardan (1501—1576). Firstly they worked on the 'dice problem' which concerned how many throws of a pair of dice would be required to produce a better than half chance of achieving a double six.

The second problem, called the 'problem of points', was about how to divide the stakes fairly if a game of chance was interrupted. Pascal and Fermat solved this for two players but not for more.

Another Frenchman, Pierre-Simon Laplace (1749—1827), continued and extended this work in his Théorie Analytique des Probabilités, and it was he who defined the probability of an event as the ratio of the number of ways the event can happen to the total possible number of outcomes. Poisson was a student of Laplace and published further important work on probability.