Aside from the elementary work by Cardano, the doctrine of probabilities dates to the correspondence of Pierre de Fermat and Blaise Pascal (1654). Christiaan Huygens (1657) gave the earliest known scientific treatment of the subject. Jakob Bernoulli's "Ars Conjectandi" (posthumous, 1713) and Abraham de Moivre's "Doctrine of Chances" (1718) treated the subject as a branch of mathematics. See Ian Hacking's "The Emergence of Probability" and James Franklin's "The Science of Conjecture" for histories of the early development of the very concept of mathematical probability.