William Petty

English physician and economist

• Born: May 26, 1623
• Birthplace: Romsey, Hampshire, England
• Died: December 16, 1687
• Place of death: London, England

A distinguished physician and scientist, Petty made demographic and economic surveys of Ireland that constituted the first practical implementation of population studies. He is also credited with introducing the labor theory of value to economics.

Early Life

Even as a young boy, Sir William Petty, the son of a clothier, demonstrated an aptitude for mechanics and mathematics, as well as a penchant for building crafts of various sorts. At the age of thirteen, he joined a merchant ship, where he had the opportunity to learn navigation skills. Petty’s experience as a seaman would serve him in the final years of his life, which he devoted to shipbuilding. Following an injury, Petty was grounded in France after only a year at sea. While there, he studied at the Jesuit college at Caen, where he received a general education.

Although Petty’s experience at sea enabled him to support himself in Europe by teaching classes on navigation, his chief aim was to become a physician. After a brief stint in the English navy, he returned to Europe to study medicine, visiting the well-known universities at Utrecht and Leiden. Subsequently, he traveled to Paris, where he met and learned from the philosopher Thomas Hobbes, whose influence on Petty’s later political theories would be profound. In 1647, Petty returned to England to continue his medical studies at Oxford. He quickly developed a reputation among other scientists as an enterprising and innovative thinker, as well as a promising physician, and he received a doctor of physic degree in 1650.

Life’s Work

After he completed his degree at Oxford, Petty’s academic and professional successes developed in rapid succession. He was appointed professor of anatomy at Oxford in 1651, in addition to holding an appointment as professor of music at London’s Gresham College from 1650 to 1659 (university courses in music at the time were actually more concerned with philosophy and physics than with composition or performance). Petty’s most enduring contribution to academic thought during this time was his role as a founding member of the Royal Society . The organization was founded to pursue the “mechanical arts,” and it soon became the leading exponent of scientific thought and experimentation in seventeenth century England, including among its members such luminaries as Robert Hooke and Sir Isaac Newton.

It was Petty’s reputation as a physician, however, that brought him to the attention of Oliver Cromwell . In 1652, Petty was appointed physician-general to Cromwell’s forces during the English invasion of Ireland. Initially, Petty was assigned with reforming medical services in the military, but he soon became involved more directly with the surveying and redistribution of Irish lands. The famous Down Survey, which mapped all of Ireland in thirteen months, was the result of this assignment.

Petty’s work in Ireland established him for future historians as England’s first “econometrician,” because he surveyed the country not solely in terms of its geography but also in terms of economic and labor value. The point of Petty’s measurements was to partition Ireland under the newly established English governance in such a way as to maximize its financial and military support for the British crown. Petty’s A Treatise on Taxes and Contributions (1662) drew upon his earlier work in economic theory and made several recommendations for the taxation of Ireland, most notably the reintroduction of the poll (or “head”) tax, which levied taxes according to the sheer number of persons in a household, including children. The treatise was praised by the Royal Society as a model of economic theory, and most of its recommendations were adopted by the British government.

Petty’s economic assessment of Ireland was deeply grounded in the work on population theory (what we would now call “demographics”) that he had begun as an original member of the Royal Society. His Political Anatomy of Ireland (1672) was a landmark work in that field, assessing the geographical and economic features of Ireland in terms of its population. The study presented a comprehensive account of the country’s population, including the size of families in Ireland and the economic roles played by different segments of the population. It is likely that Petty’s expertise in this area had played an important part in securing the favor of Charles II after the Restoration of the monarchy , as Petty was knighted in 1662 despite the evident fact that he had been a staunch supporter of Cromwell.

In addition to his political and economic work in Ireland, which established him as an influential figure in British imperial policy, Petty continued for the rest of his life to engage in the kind of scientific experimentation that had become the hallmark of his tenure in the Royal Society. While in Dublin, Petty designed and built a series of catamarans, a type of sailing vessel composed of two long, narrow hulls connected by a deck. He also produced a large number of economic and scientific treatises through the end of his life, including Verbum sapienti (1665), a work that introduced the idea of national income; Quantulumcunque Concerning Money (1682); Discourse on Political Arithmetick (1690), which attempts to ascertain the population rate of London using statistical methods; Observations upon the Cities of London and Rome (1687); and A Treatise of Ireland (1687). Despite these impressive publications, most of Petty’s recommendations for fiscal reform were not carried out during his lifetime. Petty died in London on December 16, 1687.

Significance

Petty has become a controversial figure as a result of his great contribution to British imperialist policies, particularly his involvement in England’s partitioning and repopulation of Ireland after Cromwell’s invasion. Certainly, Petty’s treatises on tax collection and population studies became both the practical and the ideological foundation for England’s economic exploitation of Ireland in the seventeenth and eighteenth centuries. The harshest critics of Petty, giving him the dubious honor of naming him the creator of modern population theory, have credited him with establishing an ideological and “unscientific” science—demographics—that often still serves as the theoretical cover for acts of genocide and ethnic cleansing in the twenty-first century.

Still, although the negative effects of Petty’s work on economic and population theory cannot be ignored, there is little question that he was instrumental in bringing together the study of statistics, economics, and political theory to form a coherent discipline. He is often credited with introducing the labor theory of value, later so central to the thought of Karl Marx, into England’s political discourse. His role in establishing the Royal Society, moreover, makes him one of the leading figures in the rise of scientific thought in pre-Enlightenment Europe.

Bibliography

Aspromourgos, Tony. On the Origins of Classical Economics: Distribution and Value from William Petty to Adam Smith. New York: Routledge, 1996. A study of the development of distribution theory in seventeenth and eighteenth century England, focused primarily on Petty’s work. Includes a chapter on Petty’s life as it relates to the development of his economic theories. Bibliography, index.

Barnard, T. C. “Sir William Petty: Irish Landowner.” In History and Imagination: Essays in Honour of H. R. Trevor-Roper, edited by Hugh Lloyd-Jones, Valerie Pearl, and Blair Worden. London: Holmes & Meier, 1981. Contextualizes Petty’s economic treatises on Ireland alongside his own interests as one of the newly appointed English landowners.

Gouk, Penelope M. “Performance Practice: Music, Medicine, and Natural Philosophy in Interregnum Oxford.” British Journal for the History of Science 29 (1996): 257-288. Offers a rich and rare discussion of Petty’s significant work on acoustics while he was teaching medicine and music at Oxford and Gresham College in the 1650’s.

Hull, Charles H. “Petty’s Place in the History of Economic Theory.” Quarterly Journal of Economics (1900). Although more than a century old, this foundational article on Petty’s written work is frequently reproduced, in large part for its concise and useful overview of Petty’s biography and theoretical work.

Strauss, Erich. Sir William Petty: Portrait of a Genius. London: Bodley Head, 1954. Takes a largely positive view of Petty’s work on demographics and economic theory, paying particular attention to Petty’s lifelong interests in medicine, mechanics, and education. Illustrations.