Modern economic enquiry, as I shall try to show in this chapter, did not remain aloof from the scientific developments outlined in the last chapter. But there was, however, a considerable time–lag. The eighteenth–century founders of modern economics, F. Quesnay and Adam Smith, still kept their accounts of human behaviour as essentially distinct from the explanations of natural processes modeled after the achievements of seventeenth–century physics. It was only by the last quarter of the nineteenth century, with the advent of the Jevonian ‘mechanics of utility and self–interest’, that the mechanical model of explanation of human behaviour made a decisive headway in the province of economics.

It is highly probable that Adam Smith had no other than La Mettrie in mind when, in his important posthumous essay on the psychology of scientific discovery illustrated by the history of astronomy (1795), he referred to ‘a learned physician’ who, as he put it, ‘lately gave a system of moral philosophy upon the principles of his own art, in which wisdom and virtue were the healthful state of the soul; the different vices and follies, the different diseases to which it was subject; in which the causes and symptoms of those diseases were ascertained; and, in the same medical strain, a proper method of cure prescribed’ (EPS,47).