What is just a probability? From Laplace to Popper

The article studies the development of the concept of probability, from Laplace up to Popper. It presents the classical definition of probability and the “frequentist” conception formalised by R. von Mises. After, it discusses Keynes’ interpretation of probability and the different approaches to the subjective probability, of Ramsey, de Finetti and Savage. The axiomatization of probability calculus by Kolmogorov was a breakdown and drives to the probability-propensity of K. Popper.