ABSTRACT

In 1860 James Clerk Maxwell published a formula giving the distribution of the velocity of the molecules in an ideal gas. Maxwell's formula was correct, and provided the foundation for the development of kinetic theory, and ultimately statistical mechanics, in the late nineteenth century. But the reasoning behind Maxwell's derivation of the distribution is rather obscure.

I will argue that Maxwell was using a sophisticated method for inferring the values of probabilities that was not discovered by him, or any of his eminent predecessors, but which is rather an inheritance from the distant past. The method dates back, perhaps, to prehistoric times, where it had, as it has today, more practical uses.