HARTLEY, DAVID, was born on the 30th of August 1705, and was the bon of a derepnan of Armley in Yorkshire. !laving teen first *lusted at a private wheel, he entered, at fifteen years of age, at Jesu? College, Cambridge, and became in time a Fellow of that society. Scraplee, which would not allow him to subscribe the Thirty nlo• Articles, preveuted him from afterward. enterins the Church, as had Neu originally intended, and he applied himself to the medical profeealou. In this profession he practised with success, and attained to considerable eminence.
He commenced the composition of the work by means of which he has beame universally known—the 'Observations on Man, his Frame, his Duty, and his Expectations '—at the ago of twenty-five. It had been the subject of his thoughts even provioualy to this. He tells the world in his preface, that the fundamental idea of the work, the possibility of explaining all states of mind by association, was first suggested to him by Mr. Gay's admirable ' Essay on the Fundamental Principle or Virtue or Morality,' prefixed to Law'a translation of Archbishop King's ' Origin of Evil.' Although begun so early as 1730, the work was not finished until sixteen years after, and it was ultimately published in 1748.
Dr. Hartley was twice married, and had children by both marriages. He practised medicine 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 years.
Combining as he did with his profession the pursuit of learning, Dr. Hartley enjoyed through life the friendship of many distinguished literary Dieu of his time. Among these may be mentioned Bishops Law, Butler, Warburton, and Hoadley, Dr. Jertin, Young the poet. and ]Tooke the Roman historian. One of his children thus writes concerning the qualities of mind and heart which endeared Dr. Hartley to his private friends : "!lie thoughts were not immersed in worldly pursuits or contentions, and therefore his life was not eventful or turbulent, but placid and undisturbed by passion or violent ambition.
From his earliest youth his mental ambition waa pre-occupied by pursuits of science. His hour. of amusement were likewise bestowed upon objects of taste and sentiment. Music, poetry, and history were his favourite recreations. His imagination was fertile and correct; his language and expression fluent and forcible. His natural temper was gay, cheerful, and sociable The virtuous principles which are instilled in his works were the invariable and decided prin ciples of his life and conduct." The chief end and great achievement of Hartley's great meta physical work is the application of the principles of association to all our states of mind, or, as he himself calls them, not perhaps very happily, "our intellectual pleasures and pains." But before proceed ing to set forth and apply the principle of association, he attempts to explain physically sensations and ideas, which he resolves into vibra tions of the medullary substance. The first hints of thia his doctrine of vibrations were derived, he tells us, from Sir Isaac Newton; but, while such speculations as these do not properly belong to the province of the psychologist, it is obvious that they can never rest upon any better foundation than conjecture. The commencement therefore of Hartley'. work detracts from rather than enhances its value. But the doctrine of vibrations being dismissed, the principle of association, of which little more than hints had previously been given by Hobbes and Locke, is explained and applied by Hartley with a fullness and acuteness which will ever render the work valuable. The second part of the work is wholly occupied with natural and revealed religion.