Two generations of distinguished Swiss mathematicians. Jakob (1655–1705) and Johann (1667–1748) were the sons of a pharmacist who wanted one boy to study theology and the other medicine. Over his objections, both pursued careers in mathematics, making important discoveries in calculus, the calculus of variations, and differential equations (differential equation). They sometimes worked together, but not without friction. Johann's son Daniel (1700–82) made important contributions to fluid dynamics (see Bernoulli's principle (Bernoulli's theorem)) and probability theory. Widely admired throughout Europe, he also studied and lectured on medicine, physics, astronomy, and botany.