The orphaned son of an Anglican clergyman, David Hartley (1705-57) was originally destined for holy orders. Declining to subscribe to the Thirty-Nine Articles, he turned to medicine and science yet remained a religious believer. This, his most significant work, provides a rigorous analysis of human nature, blending philosophy, psychology and theology. First published in two volumes in 1749, Observations on Man is notable for being based on the doctrine of the association of ideas. It greatly influenced scientists, theologians, social reformers and poets: Samuel Taylor Coleridge, who named his eldest son after Hartley, had his portrait painted while holding a copy. Volume 2 is particularly concerned with human morality and the duty and expectations of mankind. Here the author is keen to show that scientific observation is not necessarily in conflict with religious conviction.