William Petty (1623 – 1687)

The listing of letters provided in this catalogue is not complete and has been identified as an EMLO Starter Catalogue. Scholars and students who are interested in working with EMLO to bring it to completion are warmly invited to be in touch.

William Petty was a natural philosopher, economist, colonial administrator, and founder member of the Royal Society. He defied his humble beginnings as the son of a clothier to reach the centre of English power, amassing huge fortunes in revenue from holdings in Ireland. A keen social reformer, he was one of the first theorists to apply statistical analysis—or what he termed ‘political arithmetick’—to questions concerning economic policy.

Petty contrived initially to escape his origins by becoming a mariner, but ended up (by way of what he came to term a ‘remarkable accident’) stranded in Normandy, where he enlisted into a Jesuit college. He travelled the continent in pursuit of a medical education, meeting Thomas Hobbes and other luminaries, and returned to England after the Restoration to take up a position as Professor of Anatomy at Brasenose College, Oxford. He was subsequently posted to Ireland to act as physician to the army, which was then enforcing the brutal Cromwellian settlement. The government was in the process of reallocating the lands forfeited by defeated rebels to (mainly protestant) English investors, and the enterprising Petty drew up a survey detailing how this could be done. To the chagrin of his detractors, the government accepted his proposal, which ensured the seizure of millions of acres of Irish land.

In 1661, Petty was elected as a member of the Irish Parliament, representing the seat of Inistioge. He wrote a number of short disquisitions on political and economic matters, including ‘The Political Anatomy of Ireland’, which proposed measures to maintain control and stability in the region, and ‘A Treatise of Taxes and Contributions’, which advocated for a more equitable system of taxation. He divided his time between London and Ireland, and was present on 28 November 1668 at the foundational meeting of the Royal Society at Gresham College. In 1676, he was appointed judge and registrar of Admiralty Court in Dublin, and over the following years began to pay increasing attention to the demographics of his cities of residence. During the 1680s he would conduct his pioneering research into the effects of population increase on urban society, which used basic statistical extrapolation from baptism and mortality records to make predictions about the present and future size of various localities. Despite his insistence that questions of political reform needed to be tied to considerations concerning population size, Petty was far from a proto-Malthusian, maintaining rather that ‘Fewness of people, is real poverty; and a Nation wherein are Eight Millions of people, are more than twice as rich as the same scope of Land wherein are but Four.’

In the letters exchanged with his cousin, Robert Southwell, Petty emerges as warm, dynamic, self-critical, and deeply invested in the upbringing of his children and nephews. Mere weeks before Petty died in 1687, the cousins were still disputing good-naturedly about logic, politics, and shipbuilding. In his social mobility, colonial ties, and determination to confront societal ills with rational calculation, Petty embodied the archetype of the seventeenth-century statesman scientist.