In this paper I will discuss the intellectual process that transformed the philosophical and controversial notion of free will, into the simplest concept of probability. Taming free will was a necessary step for social scientists that allowed to legitimate their work and reduced the complexity of human minds to numbers. But the taming had a price: free will implies intentionality and is up to us, while probabilities are simply random; they are up to nothing and no one.

The taming seemed to work well for statisticians who were interested in averages over large samples. But it did not for the new science of mathematical economics of Léon Walras, with his stronger focus on individuals, nor for those scientists who wanted to solve the dilemma of scientific determinism.

To face the conundrum, physicist such as Maxwell attempted to adapt the probabilistic taming of free will to their own discipline.

I will follow this intellectual process of domestication of a philosophical doctrine into a mathematical one, and discuss the different issues and difficulties that arose in the process.