born May 26, 1623, Romsey, Hampshire, Eng.
died Dec. 16, 1687, London
British political economist and statistician.
He gave up a life at sea to study medicine, and taught anatomy at the University of Oxford. He founded mines, ironworks, and fisheries in Ireland. He was also responsible for several inventions and was a founder of the Royal Society . Petty was an originator of political arithmetic, which he defined as the art of reasoning by figures upon things relating to government. In his best-known work, Treatise of Taxes and Contributions (1662), he favoured giving free rein to the forces of individual self-interest but declared the maintenance of a high level of employment to be a duty of the state. He also argued that the labour necessary for production was the main determinant of exchange value.