Laplace is best known for his belief in mechanical determinism, and for his foundation of probability theory upon consideration of various combinations of equipossible cases. Alternatives are shown to be equipossible by an application of the principle of indifference, and Laplace embraced the subjective air of this principle.

Laplace's determinism was based on the enormous success of Newtonian mechanics, and in particular he himself proved the mechanical stability of the solar system. He thus removed the need for the adjusting hand of god.