Sir William Petty was a sailor, physician, professor, inventor, surveyor, and member of Parliament, as well as a political economist and statistician. He was born in Romsey, Hampshire, England, on May 26, 1623. His father was a clothier, and the family had little money for the boy's education. The details of his early years are sketchy, but Petty was apparently schooled to some degree in the small village. In his writings he remembered his greatest joy as a youth was watching the different artisans--carpenters, watchmaker, blacksmiths--at their work. By the time he was 12 years old, he felt that he could have acquitted himself at any of those trades, so well did he know them by watching. But, instead, at the age of 15 he managed to get aboard a sea vessel heading for Caen in France. Once there, he educated himself in French, Latin, Greek, and mathematics, and also spent time...