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Hartley, David (1705–1757)


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 Expectations of Mankind," consists of arguments for the existence of God, a defense of the truth of Christianity, a set of rules of conduct, and an estimate of our legitimate expectations in this life and hereafter.

Hartley's merit lies not in innovation but in consolidation. Borrowing several doctrines from his predecessors, he offers a comprehensive account of human nature. He treats mind and body as parts of a coordinate system capable of influencing each other. Thus, his work is a mixture of speculative physiology and psychology. While his conclusions may be criticized for their lack of an experimental basis (although he appeals frequently to experience), he nonetheless deserves credit for supporting the conceptual ideal of a unitary system of mind and body. Hartley's theory of knowledge is John Locke's, offered in a context of religious sentiment. Despite the role that association plays in Hartley's philosophy, there is no mention of David Hume in his pages. By freeing the doctrines of learning by experience and of psychological association from skeptical associations, Hartley gave them a respectability that assured them a general currency.

The three aspects of human nature that Hartley wished to explain are sensation, motion, and the generation of ideas. With regard to sensation, he wanted to account for the way in which impressions on the senses register perceptions in the mind. He postulated, first, that the "white medullary substance" of the brain, the spinal marrow, and nerves is the immediate instrument of sensation. He then claimed that when an external object is impressed on the senses, it occasions, first in the nerves linking the senses and the brain and then in the brain, vibrations of the infinitesimal medullary particles. These vibrations are the means of conveying the sensation to the brain.

From this account of sensation, Hartley moved on to his account of the origin of ideas. Sensations may remain in the mind for a short time after the sensible object has been removed from the vicinity of the senses. By being often repeated, sensations leave in the mind certain vestiges, types, or images of themselves. These images are the simple ideas of sensation, the materials from which complex ideas are made. Once the mind is supplied with simple ideas, the association of sensations and ideas may come into play. The first requirement is that we must have a given set of sensations "a sufficient number of times." These sensations then acquire such a power over their corresponding ideas that when any member of the set is impressed on the senses, it is able to excite in the mind the rest of the corresponding ideas that belong to the set. In this way simple ideas collect and become a complex idea.

In addition to arguing for an association of sensations and corresponding sets of ideas, Hartley also argued for a kind of association that depends on the sensory vibrations. Regularly occurring sensory vibrations leave behind in the nerves miniatures of themselves which he calls "vibratiuncles"; and even as a general sensation is able to call up a corresponding set of ideas in the mind, so a sensory vibration is able to call up a corresponding set of vibratiuncles in the nerves. Similarly, a complex idea may call into being the set of vibratiuncles appropriate to the complex of sensations with which the idea corresponds. Hartley claimed that some of the vibratiuncles attending upon complex ideas may be as vivid as any of the sensory vibrations excited by the direct action of objects.

In his account of human motion, Hartley again made use of the "white medullary substance" of the brain, spinal marrow, and nerves. He postulated this substance as the immediate instrument of motion. The motor nerves link brain and muscles; motion results as vibrations pass from the brain along the motor nerves and issue in muscular action. Briefly stated, then, Hartley's general theory of motion is that when objects are impressed in the senses, the vibrations excited in the sensory nerves spill over to the motor nerves by way of the brain and the higher ganglia; this process has a consequent effect on the muscles, and a motion results. According to Hartley, there are two sorts of motion, automatic and voluntary. They are distinguished by the fact that automatic motion depends on sensation, and voluntary motion depends on ideas.

Hartley makes "automatic motion" cover a varied class, which includes such motions as the heart's beating, crying, and voluntary actions that have become habitual through repetition. Heartbeats can be fitted into his theory only by the vaguest references to the spillover effect of the vibrations occasioned by sensation and by the additional suggestion that the circulation of the blood may also cause the heart to beat. The "motion" that best conforms to the theory is a fit of crying that results from a frightening experience or from the pain of being injured. In his theory of motion, Hartley did not intend "sensation" always to be the equivalent of "perception." For instance, the motion of breathing is excited in a newborn infant by cold air and the rough handling of the midwife, sensations which, for the infant, are not perceptions of anything.

In contrast to the automatic motions that depend on sensation, there are the voluntary motions which depend on ideas. A person's will consists of one of his ideas associated with sensory and motor vibratiuncles that are strong enough to excite the motor vibrations which, in turn, issue in muscular action. A voluntary action, for Hartley, is one that follows after an idea in the mind and not as a consequence of some outside force. He made it clear that "voluntary" must not mean "uncaused," and he argued that we have no "power of doing different things, the previous circumstances remaining the same." Indeed, he stigmatizes such an account of freedom as "philosophical freedom." He freely acknowledged that he was a mechanist, but he held that practical freedom does exist, in the sense that the causes of actions may sometimes originate within a person. Nevertheless, he staunchly maintained that human action cannot be exempted from the reasonable and useful belief that everything has a cause. Indeed, he subscribed to this belief even though he knew that many of his readers would think him a greater friend to religion if he had not stated it explicitly.

Hartley distinguished seven different classes of pleasures and pains that may accompany our sensations (and consequently our ideas), and thus reinforce their affective power, namely the following: (1) those of Sensation, as they arise from impressions made on our external senses; (2) those of Imagination, as they arise from natural beauty and deformity; (3) those of Ambition, as they arise from the opinions of others concerning ourselves; (4) those of Self-Interest, as they arise from our possession (or want) of the means of happiness; (5) those of Sympathy, as they arise from the pleasures and pains of our fellow creatures; (6) those of Theopathy, as they arise from affections excited by our contemplation of Deity; and (7) those of the Moral Sense, as they arise from our awareness of moral beauty and deformity.

The classes of pleasures and pains are here arranged in an ascending order of value, from least to most valuable; and from this scale, Hartley derived the rule of life. The pleasures of sensation, imagination, ambition, and self-interest are not in themselves worthy of pursuit. But the pleasures of sympathy are worthy of pursuit in themselves and set a proper limit to our interest in the first four classes of pleasure. Moreover, the pleasures of sympathy are consistent with those of theopathy and the moral sense. Together, these last three classes of pleasure constitute, as a whole, the worthiest object of human pursuit that can be found.

See also Butler, Joseph; Locke, John; Pain; Pleasure; Priestley, Joseph; Psychology; Sensa.


The dissemination of Hartley's doctrines was aided by his enthusiastic admirer and younger contemporary, the scientist Joseph Priestley. Priestley published an abridged version of the Observations under the title Hartley's Theory of the Human Mind on the Principle of Association of Ideas (London: J. Johnson, 1775). While Priestley omitted the theory of vibrations, it is said that he was inclined to believe in it. Hartley is also the author of an Enquiry into the Origin of the Human Appetites and Affections (Lincoln, England, 1747). See also G. S. Brett, A History of Psychology, 3 vols. (London: G. Allen, 19121921), Vol. II, pp. 278286, and Howard C. Warren, A History of the Association Psychology (New York: Scribners, 1921), pp. 5064.

Elmer Sprague (1967)

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