Hartley, DAVID, philosopher, was born August 30, 1705. His father was vicar of Armley, in Yorkshire. At fifteen he entered Jesus College, Cambridge, and became a Fellow of the college. He studied at first for the church, but, dissenting from some points in the Thirty-nine Articles, he abandoned his original intention. In his mature years he impugned the eternity of hell-punishment, maintaining the ultimate restoration of the lost; in all other points his published opinions coincided with the Church of England, and he continued to the last a member of the church. He finally chose the profession of medicine, in which he attained considerable eminence. He practised as a physician successively at Newark, Bury St Edmunds, in London, and at Bath, where he died on the 25th of August 1757, at the age of fifty-two.
His work on the mind, entitled Observations on Man (1749), on which his fame rests, was begun when he was about twenty-five, and occupied his thoughts for sixteen years. The first part relates to the constitution of the human mind; the second treats of religion and morals. His handling of the mind turns throughout upon two theories or hypotheses, which have very different merits. The first is called the Doctrine of Vibrations, or a theory of nervous action analogous to the propagation of sound, the suggestion of which he owed to Newton, of whose writings he was a devoted student. His second and most valuable innovation consisted in showing that the faculties, powers, and feelings of the mind might be explained to a very wide extent by the principle of the Association of Ideas (q.v.); and it should be said that he was certainly the first to do justice to the applications of that principle to explain the phenomena of the mind.
The doctrine of vibrations supposed that when any one of the senses is affected by an outward object the effect was to set the particles of the nerve in a vibratory motion, which ran along to the brain, and produced corresponding vibrations in the cerebral substance. In like manner, when an active impulse proceeded outwards to the muscles the manner of communication along the nerves was of the same kind. He even extended these molecular vibrations to the other tissues. The dislike generally entertained towards this part of Hartley's speculations arose from a mistaken notion of its involving or favouring materialism. See G. S. Bower, Hartley and James Mill (1881).