PETTY, SIR WILLIAM

born May 26, 1623, Romsey, Hampshire, Eng. died Dec. 16, 1687, London English political economist and statistician whose main contribution to political economy, Treatise of Taxes and Contributions (1662), considered the role of the state in the economy and touched on the labour theory of value. As a young man, Petty abandoned a life at sea to take up the study of medicine at the universities of Leiden, Paris, and Oxford. He was successively a physician, professor of anatomy at Oxford, professor of music in London, inventor, surveyor and landowner in Ireland, and member of Parliament. A protagonist of the empirical scientific doctrines of the newly established Royal Society, of which he was a founder, Petty was one of the originators of political arithmetic, which he defined as the art of reasoning by figures upon things relating to government. His Essays in Political Arithmetick and Political Survey or Anatomy of Ireland (1672) presented population estimates and rough calculations of social income. His ideas on monetary theory and policy were developed in Verbum Sapienti (1665) and in Quantulumcunque Concerning Money, 1682 (1695). His most significant work, however, is his Treatise on Taxes. Petty favoured giving free rein to the natural forces of individual self- interest. Unlike liberals after Adam Smith, however, Petty considered the maintenance of a high level of employment by monetary and fiscal policies and by public works to be a duty of the state. In the Treatise, he also argued that the labour necessary for production was the main determinant of exchange value.