This book gives a voice to the entrepreneur William Petty (1623-1687) who provided information about his life ad hoc to John Aubrey. The letters are dated back to 1674, a time when Petty was on good terms with the Stuart brothers and the cognoscenti of the era, such as examples are Isaac Newton, Robert Hooke and Christopher Wren. Seventeenth-century England was a dynamic place; the Stuarts prevailed despite their absence in the 1650s; and, in that decade the Commonwealth emerged, and change was radical in social and religious domains under Oliver Cromwell and his fellow Parliamentarians. A brilliant man of the era was William Petty (1623-1687), the son of a Hampshire wool merchant Petty qualified in medicine at Oxford University. Petty was also an entrepreneur who went on to be knighted by Charles II at the 'instauration' of the Royal Society in 1662.