Blaise Pascal

Blaise Pascal (1623–1662) was a French prodigy who packed several careers into a short, intense life: mathematician, physicist, inventor, and eventually a fiery religious philosopher. He built a working mechanical calculator as a teenager and helped invent probability theory — then largely abandoned maths to write about faith. He died at just 39.

An idea for the ages

Pascal's triangle — that endless pyramid of numbers where each entry is the sum of the two above it — hands you the coefficients of the binomial expansion for free. But his most influential work came from a letter exchange with Pierre de Fermat about how to fairly split the stakes in an interrupted gambling game. Between them, in those letters, they founded the mathematical theory of probability. His name is also stamped on the SI unit of pressure, the pascal.

Pascal turned his own probability thinking on the biggest question he could imagine, in what we now call "Pascal's Wager": he argued that believing in God is the rational bet, because the possible payoff is infinite while the cost of being wrong is small. Whatever you make of the theology, it's a striking early example of decision-making under uncertainty — using the maths of gambling to reason about the meaning of life. Not bad for a man who also built a calculator to help his tax-collector father with sums.