These explanations define and characterize the task which was proposed to himself by the author of the { x} present treatise, and which he concisely expressed by naming his work an Analysis of the Phenomena of the Human Mind. It is an attempt to reach the simplest elements which by their combination generate the manifold complexity of our mental states, and to assign the laws of those elements, and the elementary laws of their combination, from which laws, the subordinate ones which govern the compound states are consequences and corollaries.
The conception of the problem did not, of course, originate with the author; he merely applied to mental science the idea of scientific inquiry which had been matured by the successful pursuit, for many generations, of the knowledge of external nature. Even in the particular path by which he endeavoured to reach the end, he had eminent precursors. The analytic study of the facts of the human mind began with Aristotle; it was first carried to a considerable height by Hobbes and Locke, who are the real founders of that view of the Mind which regards the greater part of its intellectual structure as having been built up by Experience. These three philosophers have all left their names identified with the great fundamental law of Association of Ideas; yet none of them saw far enough to perceive that it is through this law that Experience operates in moulding our thoughts and forming our thinking powers. Dr. Hartley was the man of genius who first clearly { xi} discerned that this is the key to the explanation of the more complex mental phenomena, though he, too, was indebted for the original conjecture to another wise forgotten thinker, Mr. Gay. Dr. Hartley's treatise ("Observations on Man") goes over the whole field of the mental phenomena, both intellectual and emotional, and points out the way in which, as he thinks, sensations, ideas of sensation, and association, generate and account for the principal complications of our mental nature. If this doctrine is destined to be accepted as, in the main, the true theory of the Mind, to Hartley will always belong the glory of having originated it. But his book made scarcely any impression upon the thought of his age. He incumbered his theory of Association with a premature hypothesis respecting the physical mechanism of sensation and thought; and even had he not done so, his mode of exposition was little calculated to make any converts but such as were capable of working out the system for themselves from a few hints. His book is made up of hints rather than of proofs. It is like the production of a thinker who has carried his doctrines so long in his mind without communicating them, that he has become accustomed to leap over many of the intermediate links necessary for enabling other persons to reach his conclusions, and who, when at last he sits down to write, is unable to recover them. It was another great disadvantage to Hartley's theory, that its { xii} publication so nearly coincided with the commencement of the reaction against the Experience psychology, provoked by the hardy scepticism of Hume. From these various causes, though the philosophy of Hartley never died out, having been kept alive by Priestley, the elder Darwin, and their pupils, it was generally neglected, until at length the author of the present work gave it an importance that it can never again lose. One distinguished thinker, Dr. Thomas Brown, regarded some of the mental phenomena from a point of view similar to Hartley's, and all that he did for psychology was in this direction; but he had read Hartley's work either very superficially, or not at all: he seems to have derived nothing from it, and though he made some successful analyses of mental phenomena by means of the laws of association, he rejected, or ignored, the more searching applications of those laws; resting content, when he arrived at the more difficult problems, with mere verbal generalizations, such as his futile explanations by what he termed "relative suggestion." Brown's psychology was no outcome of Hartley's; it must be classed as an original but feebler effort in a somewhat similar direction.