David Hartley, the association psychologist and moral philosopher, was born in Luddenden, Halifax, England, and was educated at the Bradford grammar school and Jesus College, Cambridge. He was elected a fellow of Jesus but lost his fellowship when he married. He did not take holy orders, probably because of doctrinal scruples. Although he never received a medical degree either, he became a physician and practiced medicine in, successively, Newark, Bury St. Edmunds, London, and Bath. He was a friend of bishops Butler, Law, and Warburton.

Hartley's contribution to philosophy is his treatise Observations on Man, His Frame, His Duty and His Expectations (London, 1749). The first part, called "Observations on the Frame of the Human Body and Mind," is Hartley's exposition of the doctrines of vibration, association, and the seven classes of intellectual pleasures and pains. The second part, called "Observations on the Duty and...