Classics in the History of Psychology

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Christopher D. Green
York University, Toronto, Ontario

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History of Psychology: A Sketch and an Interpretation
Volume II

James Mark Baldwin (1913)


Early Empiricism, Naturalism, Materialism.

Psychology as Empirical Theory of Knowledge. -- In John Locke (1632-1704) the full empirical point of view revealed itself. Locke limits the problem to the events of the inner life; and uses the method of observation and induction. He attempts to treat of the actual sources of knowledge by a scientific method, as proposed by Francis Bacon.[1]

Moreover, he transferred the problem of the origin of knowledge, of all knowledge, from metaphysics to fact; from theories of divine illumination, pre-established harmony, and innate ideas, to hypotheses based on children, animals, and primitive men. Passing from this examination of actual knowledge, he proceeds to the more critical and epistemological questions of its validity and applications.

Pursuing what he describes as this "sober method of investigating the origin and connection of our ideas," Locke distinguishes between "simple" and "complex ideas." Simple ideas, which are those of immediate [p. 2] the "external sense" -- and belonging to the external world -- or through the "internal sense," and belonging to the inner world of the mind itself. This latter, the sphere of the internal sense, is that of "thought" as defined in the system of Descartes; the external corresponds to the system of nature or "extension."

In this conception of simple, underived, original elements or data of consciousness, the basis is laid for the work of qualitative and analytic psychology, one of the problems of which has remained that of determining these original elements.

In this general position, certain other problems were raised. The mind is conceived of as having certain "powers" native to it. But there is only the one agent or person, who has ideas through the use of all the powers or faculties. These latter are simply its ways of acting. It may be aroused in the way of sensation and perception, in the way of memory, of imagination, of will, etc. This is Locke's refutation of the "faculty psychology" of Scholasticism, afterwards continued by Wolff.

Judged by their internal characters, the simple ideas of the external sense show different marks. They have "primary " and "secondary qualities," both attributed to the external object.[2] The primary qualities are those which reproduce essentially external conditions--extension, resistance, movement, etc. These are the qualities by reason of which the external object is what it is, as independent of perception. The secondary qualities, on the other hand, are those in which the [p. 3] process of perception itself has a part--such as colour, taste, position. In the primary qualities the reality of the "extension" of Descartes is vindicated. In the secondary, the variations arise which produce relativity and illusion.

Locke does not stop, with Hobbes, at a mechanical view of the play of ideas. He finds a further and higher power of the mind: that of "reflecting upon the course of ideas." Beyond ideation there is reflection. Ideas are the "objects of the understanding when it thinks."

Reflection is the source of a new series of ideas--general, abstract, universal--which involve relations between and among simpler ideas. Such are the ideas of cause, substance, relation itself. Locke's distinction between sensation and reflection reminds us of that of Leibnitz between perception and apperception; and it is likely that the latter is a revision of the former, for Leibnitz kept Locke's Essay constantly in mind.

The ideas of reflection are not innate; there are no innate ideas. This Locke argues with great wealth of inductive proof; but by innate ideas he generally means actual conscious presentations or images. He shows that children lack innate ideas in this sense. This Leibnitz was able to meet by postulating "unconscious presentations," which slumber in obscure form and in the undeveloped psychic modes, but are still essentially innate. The admission by Locke of certain inherent "powers " or functions would seem to leave open the door for the later critical distinction between the a posteriori or experiential content, and the a priori or native form, in the structure of knowledge.

The motive of Locke is clear, however: it is the [p. 4] general refutation of rationalism. For to all rationalism it is essential that the reason be not dependent upon purely sensational or empirical data, either in its origin or in its products. Locke's aim was to establish empiricism.

To Locke, further, reflection was largely a passive power; it was refection upon the course or flow of our ideas, not reflection as itself determining this flow or course to be what it is. Reflection is an "inner sense." The actual flow of ideas is due to the laws of association, a term first used, though in a special reference, by Locke. So while the mind reserved the power of thought or reflection, still all other contents, together with the laws of organisation of these contents in complex ideas, were due to sensations and their interaction. As over against rationalism, the programme of a mental mechanics, a pure "presentationism," was suggested in anticipation; and at the hands of Hume and the Associationists, this programme was to be speedily realised.

Locke's Essay contains a wealth of sound psychological observation. His analysis of the ideas of reflection, the categories, is the first of its sort: analytic, empirical, psychological. He accepts the certainty of the existence of the mind, immediately given, as Descartes declared. The existence of the external world, on the contrary, was derived; It depended upon the character of "liveliness " attaching to certain sensations.

The active powers, feeling and will, have scant notice. They have not the importance that cognition has in a polemic against rationalism. Pleasure and pain are simple ideas or sensations. Will is an original movement of the mind, an effort motived by
[p. 5] "uneasiness." Both feelings and conations, or efforts, like other simple ideas, are involved in the processes of association.

Locke focused certain problems by means of experiment also. His proof of the relativity of temperature is classical: he pointed out that the two hands feel the same water as of different temperatures when they themselves are. He also demonstrated the limited area or span of consciousness, by showing the inability of the attention to take in more than a certain number of items or units exposed simultaneously to the eye.

Locke's significance for psychology, in sum, resides primarily in the empiricism of his point of view. This made possible an analytical method, as expounders of Locke generally recognise. But it is not so generally remarked that Locke's research was one of origins also. He aimed to show the nature and validity of ideas as dependent upon their origin and development. This is the point of view, in so far, of modern genetic psychology. The analytical empiricism of Locke was taken up and carried forward by his successors; but the genetic factor remained undeveloped until the theory of evolution came to reveal its true value.

Sensationalism and Associationism. -- David Hume (1711-1776), the greatest of the Scottish philosophers, developed Locke's position in the two directions in which empiricism still retained rationalistic features.

First, the distinction between sensation and reflection, sense and reason, was abolished; even in the functional form of it that Locke's theory of mental "powers" had retained. Second, a thorough-going "associationism," essentially mechanical in character, took the place of Locke's Cartesian theory of self- [p. 6] consciousness. The synthetic activity of the mind was replaced by the association of ideas.

Hume entirely denied any effective role to mental function or process as such. He distinguished in mental contents two grades, "impressions" and "ideas." But he distinguished among impressions, the first data of experience, "inner" and "outer" impressions. Inner impressions were those of the inner sphere itself, such as pleasures, pains, efforts, etc.; and outer impressions were those received by the senses and having the imprint of externality. All possible materials of knowledge, of experience throughout, arise in impressions; and since the term sensation is commonly used for such first data of knowledge, "sensationalism'' became the term applied to the resulting theory of knowledge. Rationalism asserts the originality of reason, and explains away or ignores sensation; sensationalism asserts the originality of sensation, and explains away or derives the reason.

The term "idea " is confined by Hume to the derivatives or revived contents of mind in which impressions reappear. They take on various forms of revival and composition. In general, the "idea" of Hume corresponds to the "complex idea" of Locke, and "impression" to Locke's "simple idea." In the use of the term impression itself, the passivity of the mind, its mere impressiveness, is emphasised. As a tabula rasa, it receives or suffers impressions.

Ideas, the contents of imagination, differ from impressions, the contents of sensation, in vividness or intensity. According to Hume the most vivid idea is less so than the least vivid impression. This difference is, therefore, the distinguishing one.

The course of ideas--their flow, connection, composi- [p. 7] tion--was ruled by the principle of association. In this, a mental principle was substituted for the material inertia of the brain, postulated by Hobbes. It also replaced, as we have already seen, the active principle of thought of Descartes. For the first time, a psychological mode of organisation was suggested to justify a naturalistic view of conscious process. Association came to be recognised by a great school of thinkers as the one principle of mental change and movement, somewhat as attraction was found to be in the domain of the physical.

Hume recognised three cases of association, generalised in laws: the cases of "resemblance," "contiguity " in space and time, and "cause and effect." As compared with Aristotle's classification, this omits "contrast," and includes the new case of " cause and effect." In the tracing out, the detection as it were, of association in the more complex and synthetic products of the mental life--such as the ideas of the self, the external world, etc.--Hume showed his analytical ability and consistency. He was the first, and remains one of the greatest, of those psychological naturalists who have consistently applied a positive method. Association seemed to supply the hint to the process of progressive mental accommodation, as natural selection subsequently supplied the hint to that of organic adaptation. It gave to naturalism a positive weapon, to mental process a positive lawfulness. And it remains the resort of all those psychologists who find in apperception, mental causation, subjective synthesis, etc., resort to new modes of obscurantism, such as the natural selectionist finds in the newer modifications of vitalism. It was not until the conception of a structural psychology, based upon the analogy of the [p. 8] mechanical processes of physics, was succeeded by that of a functional and truly genetic psychology, to which mechanism was not the last word, that association was finally assigned a more modest role. The "mechanics of ideas" of Herbart and the radical "composition theory" of mind of Spencer were first to have their development, both based upon the principle of association.

Hume worked out, in detail, association theories of the higher ideas or concepts of thought, classed by him under the terms" relations," " modes," and " substances." The "self" became a "bundle" of associated ideas; in this the "presentation" theories were anticipated, which were later on brought into direct opposition to "activity" theories. The belief in reality, both external and internal, is ascribed to the vividness of certain impressions, whose force is transferred to associated ideas or memories; these latter are thus distinguished from mere ideas of fancy. Judgments of reality involve a similar reference to impressions. The grounds of belief in reality are in this way carried back to the characters or coefficients of sense-impressions The persistent character of external reality--looked upon as having continuing existence apart from perception--is due to the imagination, which connects recurrent impressions in an experience equivalent to that of an identical persistent object.[3] The logical relations, so-called, such as that involved in the universal, are also brought under association The quality white, for example, is not a logical universal, but an "abstract idea," due to the association by resemblance of many white objects. In this procedure, [p. 9] Hume foreshadows the development of what is known as "psychologism" in logic.

In Hume the emphasis continues to rest upon cognition upon ideas, and upon the theory of knowledge. His interest, like that of Locke, was in the refutation of rationalism. Accordingly, we find scant notice of feeling and will. Hume developed Locke's position that pleasure and pain were simple ideas or impressions --internal in character--subject to the laws of association. The emotions are impressions aroused by ideas, with which they become straitly[sic] associated. Acts of will are similar internal impressions aroused by feeling; they are capable of reproduction as ideas, and are subject to association with other ideas.

Much of the reasonableness of Hume's theory arises, however, from a further almost tacit assumption, by which he supplemented the principle of association. He assumes and employs to the utmost the principle of "custom" or "habit." Habit works wonders in his hands--just the wonders that the Lockian "inner sense," the Cartesian "reason," and later on the Kantian "formal categories," worked in turn. By habit, said Hume, the associated impressions and ideas are bound into aggregates and wholes, to which belief and custom attach; and in which the original details of structure and complexity are lost. The complex ideas, thus welded and fused by habit, hare the unity and certainty of the "clear and distinct" ideas of reason described by Descartes and Leibnitz, and conceal their origin from impressions and presentations. Things repeatedly and invariably associated together become parts of one whole over which habit overflows, and to which habit gives the sanction of a universal and necessary connection. All necessity attaching to the course [p. 10] of events, either internal or external, is due to habit. What we are in the habit of finding we take to be true and necessary.

In this Hume struck upon one of the most fertile ideas of modern psychology and philosophy.[4] Its philosophical significance is seen in the development of empirical theories of knowledge and of morals in which the formal element in truth and duty is attributed to the consciousness of habit. Individual habit passed over into the "inherited habit" by which Spencer accounted for the a priori "forms " of Kant, and into the "social custom" by which the utilitarian moralists accounted for the imperative of the practical reason.

In this way, rational form, intuition, the idea, are accounted for by individual or racial habit, or by the two combined.

Its psychological significance, apart from the theory of knowledge, resides in the suggestion that in habit, considered as a tendency of a functional sort, the inner principle as such is in a sense located; it is to be sought in the active and synthetic side of consciousness. It brings this side of the mental life within the range of observation, and substitutes something actual in consciousness for the postulates of logical and metaphysical theory. The concept of habit has been developed enormously in a group of modern theories of [p. 11] the "motor" or dynamic type, which account for the whole range of the synthetic function--attention, apperception, interest, generalisation, thought, the self--in terms of the consciousness of movement and activity.[5]

By the way of summary we may say that Hume is to be considered both by reason of his conception and because of his method, one of the prophets of modern psychology; In conception, he held to a naturalism which submitted the mind as a whole--the self as well as its knowledge--to investigation by the same right as other things in nature. In method, he was an experimentalist, a positivist, admitting- no intrusions from metaphysics, no dogmatic assumptions. His results were, of course, in a measure personal to him, and as is the case with those of all pioneers, they have been criticised, developed, in part rejected. But in his principles of association and habit, no less than in his sensational theory of knowledge, Hume worked out views which have been and still are of enormous influence.

His psychology is one of those systems whose very radicalness and freedom from ambiguity make them typical and influential not only positively, but also as targets for the practice of riflemen generally. His soberness and homely clarity of style--qualities similar to those of Locke--gave his views universal currency; and it is to the reaction against Hume that the next great departure in rationalism, the Criticism of Kant, was directly due.[6] [p. 12]

Condillac, Etienne (1715-1780) sensationalist theory was transferred to France. In Great Britain, especially in Scotland, a reaction toward spiritualism showed itself, as a protest against the materialistic consequences drawn from the premises of Hume.

Condillac pressed the sensationalistic analysis to its conclusion. He dropped Hume's principle of habit, and with it all effort to preserve mental synthesis as such. Sensations alone, accompanied by feeling, reproduced as ideas, and dominated by association, account for the entire mental life. All the so-called "rational" products of the mind are groupings of sensations, effected by association.

Condillac did not concede the legitimacy either of the supposition of an external world apart from sensation, or of an inner principle as such. These assumptions, said he, come from the needs of our practical life. We act upon a world, or seem to, and it is we who so act, or seem to; but there is nothing in knowledge to justify either of these assumptions--either the "we" or the "world." By the famous figure of a statue alive, but without experience, Condillac illustrated the development of the entire mental life, through the introduction into the statue merely of the senses and the rules of association.

Condillac has the importance that extremes usually have: that of isolating a view, and freeing it of all ambiguity. He also suggested the new lines of departure to be taken in the movements of phenomenalism and materialism. The first of these appeared when the "primary qualities" of matter--resistance, extension, [p. 13] [figure] [p. 14] etc.--were reduced to complexes of sensations and ideas, as the self had already been reduced by Hume. The conclusion is that the flow of states within consciousness is all that we really have--mere phenomena, appearances--and that there is no reality behind them. This sort of analysis was also made in England by Berkeley, an elder contemporary of Hume, to whom we are to return.

Further, impulse, and with it will, is the presence in mind of a dominant idea of advantage or pleasure; and attention is the presence in mind of an intense sensation or presentation.[7]

Such phenomenalism, it is clear, reinstated the point of view of the Sophistic dictum, Homo mensura omnium, but with the reinforcement that came from the intervening thought of centuries in defining and isolating the subjective point of view. The Sophists were pre-dualistic; the modern phenomenalists, post-dualistic. The Sophists were unable to pass to a clear distinction between mind and body, either by sense or by reason; ideas alone remained to them. The phenomenalist argues away the distinction by consciously denying both the substances mediated by ideas; to them also ideas alone remained. The difference shows itself, moreover, in the greater individualism of modern phenomenalism. The inner life had become that of the private and single self, the area of personal consciousness. Phenomena, thus restricted to the individual, had the greater relativity and the lesser value. One goes on logically to solipsism. As theory of the mental life, it supplied the psychology of agnosticism.

Pure phenomenalism, however, in the form of [p. 15] solipsism, is rarely held. The tendency is to use this sort of analysis in the interest of a philosophy which denies one sort of reality, in order to reinforce its assertion of the other. In Berkeley, it was mind which profited by the subjective analysis of body; in the materialists, to whom we next turn, it is body which is retained at the expense of mind.

Eighteenth-century Materialism.--Among writers in England, Hartley (1704-1757), a contemporary of Hume, and Priestley (1733-1804) took the step from sensationalism to materialism; in France, it was taken by Lamettrie, a contemporary of Condillac.

Intelligence, comprising all the faculties of reflection and volition, having been reduced to sensations, and the self to a complex thereof, it was easy to substitute for the impression in the mind its cause in the brain. The brain state, the organic counterpart of the sensation, is part of the physical world; it reflects the physical excitation of the senses. The whole person then, not merely the body; the sensation, not merely the exciting cause, is part of the material system of nature.

It was natural, also, in order to give greater positiveness to the law-abiding character of mental phenomena, to ground the association of ideas in the material connections of the brain. Priestley especially developed the idea that the organisation of mental states reflected that of the brain centres. He explicitly taught the identity of mind and brain. For Hartley and Priestley, the continuity of mind was in principle that of brain processes; ideas as states of memory and imagination were due to the reinstatement of brain states according to this law. Thus the last shade of the distinction between sensation and idea disappeared.

[p. 16] The further development of materialism is mainly of philosophical interest. It was carried forward by Diderot, Holbach, and the French Encyclopædists.[8]

The aspect of their view that is of psychological significance is the supposed parallelism it suggested between mental and physical states, a suggestion developed into what is now known as "psychophysical parallelism."[9] This principle does not associate itself necessarily with materialism; Spinoza and Leibnitz had already suggested it in their theories of correlated "attributes " and of "harmony." It allowed also of an interpretation of the mind in terms of the aggregation of psychic atoms--"least states" correlated with least physical changes or vibrations--by Diderot, which anticipated a new pan-psychism and a new positivism. Spencer, later on, postulated an "elementary sensation" correlated with an "elementary nervous shock," in much the same sense.[10] Materialists like Holbach went beyond this, teaching the positive identity of mind and body, and the metaphysical existence of matter and motion. In the neat phrasing of Harms, "mechanical physics supplied the metaphysics of materialism" (loc. cit., p. 323).


[1] Locke's great work is entitled An Essay concerning Human Understanding (1690).

[2] For a note on the history of the distinction, and of the terms primary and secondary dualities, see Klemm, loc. cit., p. 282, who cites Baumke.

[3] Later thinkers fall back upon much the same psychological factors; cf. the writer's Thought and Things, Chap. X, Vol. I.

[4] Of the historians of psychology, Harms alone, I think, speaks of this (Harms, loc. cit., pp. 311 ff.). Dessoir seems completely unaware of this part of Hume's psychology; and Klemm makes no note of it that I can find. In fact, however, the "habit" of Hume supplies a most interesting transition from the "inner sense" of Locke to the purely mechanical processes of Condillac. An acute exposition and criticism of Hume's view is to be found in T. H. Green's Introduction to The Philosophy of David Hume.

[5] All the writers of the " motor " school are not, of course, so radical in their use of the principle. Ribot makes thorough-going use of it; Fouillee and Munsterberg employ it more incidentally. In the present writer's Mental Development in the Child and the Race (1st ed., 1895) it was given the wide scope indicated in the text.

[6] More than once has philosophical rationalism found it convenient to "introduce" itself by a criticism of Hume. See T. H. Green's Introduction to the Philosophy of David Hume.

[7] Both being positions made use of in the modern "presentational" and Herbartian theories.

[8] Baron von Holbach's Systeme de la Nature (1770) is one of the classical statements of Materialism. He postulated qualitatively different atoms, in the sense of chemical elements.

[9] See below, Chapter V, of this volume.

[10] So comparative psychology may assume in low organisms a "nervous analogue" to elementary states of pleasure and pain. See the writer's Mental Development in the Child and the Race, 1st ed. (1895).