Jean le Rond D'Alembert, French mathematician and philosopher, c 1750.
© Science Museum / Science & Society Picture Library
Reputedly the illegitimate son of aristocrats, Jean le Rond D'Alembert (1717-1783) was raised by a glazier in Paris. After initially studying law and medicine, D'Alembert dedicated himself to mathematics and made important contributions to mechanics. He also asisted Diderot in compiling his 'Encyclopedie' of 1751.