Portrait of the French mathematician, physicist and philosopher Blaise Pascal (1623-1662). Pascal was educated by his father and showed very early his mathematical talent. In 1640 he published a treatise on conic sections in which he deduced 400 propositions. The most famous was the Pascal's theorem also known as the problem of Pappus. In 1642 Pascal invented the first calculating machine which could add and subtract. His interest in hydrostatics led him to discover Pascal's law which stated that the pressure exerted on a confined fluid is constant in all directions. Together with Fermat he is also considered a pioneer of the theory of probability.