1. The view that psychology is an empirical science which deals, not with a limited group of specific contents of experience, but with the immediate contents of all experience, is of recent origin. It encounters even in the science of today hostile views, which are to be looked upon, in general, as the survivals of earlier stages of development, and which are in turn arrayed against one another according to their attitudes on the question of the relations of psychology to philosophy and to the other sciences. On the basis of the two definitions mentioned above (§ 1, 1) as being the most widely accepted, two chief forms of psychology may be distinguished: metaphysical psychology and empirical psychology. Each is further divided into a number of special tendencies.

Metaphysical psychology generally values very little the empirical analysis and causal interpretation of psychical processes. Regarding psychology as a part of philosophical metaphysics, the chief effort of such psychology is directed toward the discovery of a definition of the "nature of mind" which shall be in accord with the metaphysical system to which the particular form of psychology belongs. After a metaphysical concept of mind has thus been established, the attempt is made to deduce from it the actual content of psychical experience. The characteristic which distinguishes metaphysical psychology from empirical psychology is, then, to be found in the attempt of metaphysical psychology to deduce psychical processes, not from other psychical processes, but from some substratum entirely unlike these processes themselves: either from the manifestations of a special mind-substance, or from the attributes and processes of matter. According as the substratum of psychical processes is defined in the one way or the other, metaphysical psychology branches off in two directions. In the first place, it may become spiritualistic psychology, in which case it considers psychical processes as the manifestations of a specific mind-substance and regards this mind-substance either as essentially different from matter (dualism), or as related in nature to matter (monism or monadology). The metaphysical tendency of spiritualistic psychology is expressed in the assumption of the supersensible nature of mind, and in connection with this, the assumption of the immortality of the mind. Sometimes the further notion of preexistence is also added. In the second place metaphysical psychology may become materialistic psychology. It then refers psychical processes to the same material substratum as that which natural science employs for the hypothetical explanation of natural phenomena. According to this view, psychical processes, like physical vital processes, are connected with certain organizations of material particles which are formed during the life of the individual and broken up at the end of that life. The metaphysical character of this form of psychology is determined by its denial that the mind is supersensible in its nature as is asserted by spiritualistic psychology. In order to make good its position such a materialistic form of psychology resorts to one of the two following devices. It may explain the content of psychological experience by means of a vague and inexact theory of molecular processes in the brain (mechanical materialism); or it may regard sensation as a necessary attribute, either of all material particles, or else of brain molecules in particular, in which case it treats all complex mental processes as combinations of such sensations, and explains their rise as the result of various combinations of physical brain processes (psycho-physical materialism). Materialism in its various forms and spiritualistic psychology in its various forms, agree in that they do not seek to interpret psychical experience by experience itself, but rather attempt to derive this experience from some kind of presuppositions in regard to hypothetical processes which are assumed to take place in some metaphysical substratum.

2. From the strife that followed these attempts at metaphysical explanation, empirical psychology arose. Wherever empirical psychology is consistently carried out, it either strives to arrange psychical processes under general concepts derived directly from the interconnection of these processes themselves, or it begins with certain of these processes, as a rule with the simpler ones, and then explains the more complicated processes as the results of the interaction of those with which it began. There may be various fundamental principles upon which to base such an empirical interpretation, and thus it becomes possible to distinguish several varieties of empirical psychology. In general, these may be classified according to two principles of division. The first principle has reference to the relation of inner and outer experience and to the attitude which the two branches of empirical science, namely natural science and psychology, take toward each other. The second principle refers to the facts themselves, or to the derived concepts which are employed in the interpretation of mental processes. Every system of empirical psychology takes its place under both of these principles of classification.

3. On the general question as to the nature of psychical experience there stand over against each other the two forms of psychology already mentioned (§ 1) on account of their decisive significance in determining the problem of psychology: psychology of the inner sense, and psychology as the science of immediate experience. The first treats psychical processes as contents of a special sphere of experience coordinate with the sphere of experiences which are derived through the outer senses and are assigned to the natural sciences. It also holds that the two spheres of experience though coordinate are totally different from each other. The second form of psychology, namely psychology as the science of immediate experience, recognizes no real difference between inner and outer experience, but finds the distinction only in the different points of view from which unitary experience is considered in the two cases.

The first of these two varieties of empirical psychology is the older. It arose primarily through the effort to establish the independence of psychological observation in the face of the encroachments of natural philosophy. In thus coordinating natural science and psychology, it sees the justification for the equal recognition of both spheres of science in the fact that they have entirely different objects and modes of perceiving these objects. This view has influenced empirical psychology in two ways. First, it favored the opinion that psychology should employ empirical methods, at the same time holding that these methods, like psychological experience, should be fundamentally different from those of natural science. Second, it gave rise to the necessity of showing some connection or other between these two kinds of experience, which were supposed to be different. In response to the first demand, it was chiefly the psychology of the inner sense that developed the method of pure introspection (§ 3, 2). In attempting to solve the second problem, this psychology was necessarily driven back to a metaphysical basis, because of its assumption of a difference between the physical and the psychical contents of experience. For, from the very nature of the case, it is impossible, from the position here taken, to explain the relations of inner to outer experience, or the so-called "interaction between body and mind", except through metaphysical presuppositions. These presuppositions must then, in turn, affect the psychological investigation itself in such a way as to result in the importation of metaphysical hypotheses into it.

4. Essentially distinct from the psychology of the inner sense is the form of psychology which defines itself as "the science of immediate experience". Regarding, as it does, outer and inner experience, not as different parts of experience, but as different ways of looking at one and the same experience, this form of psychology can not admit any fundamental difference between the methods of psychology and those of natural science. It has, therefore, sought above all to cultivate experimental methods which shall lead to just such an exact analysis of psychical processes as that which the explanatory natural sciences undertake in the case of natural phenomena, the only differences being those which arise from the diverse points of view. This form of psychology holds, furthermore, that the special mental sciences which have to do with concrete mental processes and creations, stand on the same basis as itself, that is, on the basis of a scientific consideration of the immediate contents of experience and of their relations to acting subjects. It follows, then, that psychological analysis of the most general mental products, such as language, mythological ideas, and laws of custom, is to be regarded as an aid to the understanding of all the more complicated psychical processes. In its methods, accordingly, this form of psychology stands in close relation to other sciences: as experimental psychology, to the natural sciences; as social psychology, to the special mental sciences.

Finally, from this point of view, the question of the relation between psychical and physical objects disappears entirely. They are not different objects at all, but one and the same content of experience. This content is examined in the one case, that is, in the natural sciences, after abstracting from the subject. In the other case, that is, in psychology, it is examined in its immediate character and its complete relation to the subject. All metaphysical hypotheses as to the relation of psychical and physical objects are, when viewed from this position, attempts to solve a problem which never would have existed if the case had been correctly stated. Psychology must then dispense with metaphysical supplementary hypotheses in regard to the interconnection of psychical processes, because these processes are the immediate contents of experience. Another method of procedure, however, is open since inner and outer experience are supplementary points of view. Wherever breaks appear in the interconnection of psychical processes, it is allowable to carry on the investigation according to the physical methods of considering these same processes, in order to discover whether the absent link can be thus supplied. The same holds for the reverse method of filling up the breaks in the continuity of our physiological knowledge, by means of elements derived from psychological investigation. Only on the basis of such a view, which sets the two forms of knowledge in their true relation, is it possible for psychology to become in the fullest sense an empirical science. Only in this way, too, can physiology become the true supplementary science of psychology, and psychology, on the other hand, the auxiliary of physiology.

5. Under the second principle of classification mentioned above (2), that is, the principle based on the facts or concepts with which the investigation of psychical processes begins, there are two varieties of empirical psychology to be distinguished. They are, furthermore, successive stages in the development of psychological interpretation. The first corresponds to a descriptive, the second to an explanatory stage. The attempt to present a discriminating description of the different psychical processes, gave rise to the need of an appropriate classification. Class-concepts were formed, under which the various processes were grouped; and the attempt was made to satisfy the need of an interpretation in each particular case, by subsuming the components of a given compound process under their proper class-concepts. Such concepts are, for example, sensation, knowledge, attention, memory, imagination, understanding, and will. They correspond to the general concepts of physics which are derived from the immediate perception of natural phenomena, such as weight, heat, sound, and light. Like those concepts of physics, the derived psychical concepts mentioned may serve as a first means of grouping the facts, but they contribute nothing whatever to the explanation of these facts. Empirical psychology has, however, often been guilty of confounding description with explanation. Thus, the faculty-psychology considered these class-concepts as psychical forces or faculties, and referred psychical processes to their separate or united activity.

6. Opposed to this method of treatment found in descriptive faculty-psychology, is that of explanatory psychology. When consistently empirical, the latter must base its interpretations on certain facts which themselves belong to psychical experience. These facts may, however, be taken from different spheres of psychical activity, and so it comes that explanatory treatment may be further divided into two varieties which correspond respectively to the two factors, objects and subject, which go to make up immediate experience. When the chief emphasis is laid on the objects of immediate experience, intellectualistic psychology results. This type of psychology attempts to derive all psychical processes, especially the subjective feelings, impulses, and volitions, from ideas, or intellectual processes as they may be called on account of their importance for knowledge of the objective world. If, on the contrary, the chief emphasis is laid on the way in which immediate experience arises in the subject, there results a variety of explanatory psychology which attributes to those subjective activities which are not referred to external objects, a position as independent as that assigned to ideas. This variety has been called voluntaristic psychology, because of the importance which must be conceded to volitional processes in comparison with other subjective processes.

Of the two varieties of psychology which result from the different general attitudes on the question of the nature of inner experience (3), that form which we have called psychology of the inner sense commonly tends towards intellectualism. This is due to the fact that, when the inner sense is coordinated with the outer senses, the contents of psychical experience which first attract consideration are those which are presented as objects to this inner sense in a manner analogous to that in which natural objects are presented to the outer senses. It is assumed, accordingly, that the character of objects can be attributed to ideas alone of all the contents of psychical experience, because ideas are regarded as images of the external objects presented to the outer senses. Ideas are, thus, looked upon as the only real objects of the inner sense, while all processes not referred to external objects, as for example the feelings, are interpreted as obscure ideas, or ideas related to one's own body, or, finally, as effects arising from combinations of ideas.

The psychology of immediate experience (4), on the other hand, tends toward voluntarism. It is obvious that here, where the chief problem of psychology is held to be the investigation of the subjective rise of all experience, special attention will be devoted to those factors from which natural science abstracts.

7. Intellectualistic psychology has in the course of its development separated into two forms. In one form; the logical processes of judgment and reasoning are regarded as the typical forms of all psychoses; in the other, certain combinations of successive memory images distinguished by their frequency, the so-called associations of ideas, are accepted as typical. The logical theory is most clearly related to the popular method of psychological interpretation and is, therefore, the older. It finds some acceptance even in modern times. The association theory arose from the philosophical empiricism of the eighteenth century. The two theories stand, to a certain extent, in antithesis, since the first attempts to reduce the totality of psychical processes to higher processes, while the latter seeks to reduce this same totality of processes to lower and, as it is assumed, simpler forms of intellectual activity. Both are one-sided, and not only fail to explain affective processes and volitional processes on the basis of the assumption with which they start, but are not able to give a complete interpretation even of the intellectual processes.

8. The union of psychology of the inner sense with the intellectualistic view has led to a peculiar assumption which has been in many cases fatal to psychological theory. We may define this assumption briefly as the erroneous and intellectualistic attribution of the nature of things, to ideas. Not only was an analogy assumed between the objects of the so-called inner sense and those of the outer senses, but the former were regarded as the images of the latter; and so it came that the attributes which natural science ascribes to external objects, were also transferred to the immediate objects of the "inner sense". The assumption was made, accordingly, that ideas are themselves permanent things, just as much as the external objects to which we refer them; that these ideas disappear from consciousness and come back unchanged into it; that they may, indeed, be more or less intensely and clearly perceived, according as the inner sense is stimulated through the outer senses or not, and according to the degree of attention concentrated upon them, but that on the whole they remain constant in qualitative character.

9. In all these respects voluntaristic psychology is opposed to intellectualism. While the latter assumes an inner sense and specific objects of inner experience, voluntarism is related to the view that inner experience is identical with immediate experience. According to this doctrine, the content of psychological experience does not consist of a sum of objects presented to the subject, but it consists of all that which makes up the process of experience, that is, of all the experiences of the subject in their immediate character, unmodified by abstraction or reflection. It follows of necessity that the contents of psychological experience are here regarded as an interconnection of processes. Psychical facts are occurrences, not objects; they take place, like all occurrences, in time and are never the same at a given point in time as they were during the preceding moment. In this sense volitions are typical for the understanding of all mental experiences. Voluntaristic psychology, accordingly, does not by any means assert that volition is the only real form of psychosis, but merely that, with its closely related feelings and emotions, volition is just as essential a component of psychological experience as are sensations and ideas. It holds, further, that all other psychical processes are to be thought of after the analogy of volitions, they too being a series of continuous changes in time, not a sum of permanent objects, as intellectualism generally assumes in consequence of its erroneous attribution to ideas of those properties which we attribute to external objects. The recognition of the immediate reality of psychological experience renders impossible any attempt to derive the particular components of psychical phenomena from processes specifically different from the experiences themselves. It also makes it obvious that the analogous attempts of metaphysical psychology to derive all conscious processes from imaginary processes of an hypothetical substratum, are inconsistent with the real problem of psychology. While psychology concerns itself, accordingly, with immediate experience, it nevertheless assumes from the first that all psychical contents contain objective as well as subjective factors. These are to be distinguished only through deliberate abstraction, and can never appear as really separate processes. In fact, observation teaches that there are no ideas which do not arouse in us feelings and impulses of different intensities, and also that a feeling or a volition which does not refer to some ideated object is altogether impossible.

10. The governing principles of the psychological position maintained in the following chapters may be summed up in three general statements.

1) Inner, or psychological experience is not a special sphere of experience apart from others, but is immediate experience in its totality.

2) This immediate experience is not made up of unchanging contents, but of an interconnected system of occurrences; not of objects, but of processes, of universal human experiences and their relations in accordance with certain laws.

3) Each of these processes contains an objective content and a subjective process, thus including the general conditions both of all knowledge and of all practical human activity.

Corresponding to these three general principles, we have a threefold relation of psychology to the other sciences.

1) As the science of immediate experience, it is supplementary to the natural sciences, which, in consequence of their abstraction from the subject, have to do only with the objective, mediate contents of experience. Any particular fact can, strictly speaking, be understood in its full significance only after it has been subjected to the analyses of both natural science and psychology. In this sense, then, physics and physiology are auxiliary to psychology, and the latter is, in turn, supplementary to the natural sciences.

2) As the science of the universal forms of immediate human experience and their combination in accordance with certain laws, it is the foundation of the mental sciences. These sciences treat in all cases of the activities issuing from immediate human experiences, and of the effects of such activities. Since psychology has for its problem the investigation of the forms and laws of these activities, it is at once the most general mental science, and the foundation of all the others, that is, of philology, history, political economy, jurisprudence, etc.

3) Since psychology pays equal attention to both the subjective and objective conditions which underlie not only theoretical knowledge, but practical activity as well, and since it seeks to determine the interrelation of these subjective and objective conditions, it is the empirical discipline the results of which are most immediately useful in the investigation of the general problems of the theory of knowledge and ethics, the two foundations of philosophy. Thus, psychology is, in relation to the natural sciences, the supplementary science; in relation to the mental sciences it is the fundamental science; and in relation to philosophy it is the propaedeutic empirical science.

10 a. The following tabular summary presents in their systematic relation, the chief forms of psychology above described (1-3).
 
 

first, the soul as a thinking and unextended entity, and second, matter as an extended and nonthinking reality. The Cartesian system found the point of contact between these two forms of reality in a particular region of the human brain, namely, the pineal gland. The founder of modern materialism is Thomas Hobbes (1588—1679). (The ancient materialistic dualism of democrates had not yet differentiated itself from spiritualistic dualism). hobbes, together with la mettrie and holbach developed in the 18th century a mechanical materialism, while diderot and helvetius developed a psycho-physical materialism which has representatives even in present times. Spiritualistic monism first arose in the monadology of leibniz. In modern times this has been taken up by herbart and his school, by lotze, and others. The establishment of the psychology of the inner sense may be properly attributed to John Locke (1632 —1704). This form of psychology has been defended in modern times, to some extent by kant, and with special emphasis by Eduard Beneke (1798—1854), K. fortlage, and others. Modern faculty-psychology arose with the work of Christian Wolff (1679—1754), who distinguished as the chief faculties, knowledge and desire. Since the time of Tetens (1736—1805) three faculties have been more commonly accepted than wolff's two. plato named these three, as did also kant. They are knowledge, feeling and desire. Logical intellectualism is the oldest of the explanatory forms of psychology. This corresponds directly to the popular interpretation of psychical processes. The earlier empiricists, as for example locke, and even Berkeley (1684—1753) who in his "Essay towards a New Theory of Vision" anticipates modern experimental psychology, are to be classed as representatives of logical intellectualism. This view is at the present time to be found in the psychological discussions indulged in by physiological writers, when they treat of such topics as sense perception. Among the philosophical representatives of this logical intellectualism in our day, one must mention especially franz brentano and his school. Association psychology is first found in the works of two writers who appear at about the same time, namely, David Hartley (1704—1757) and David Hume (1711—1776). These two writers represent, however, two different tendencies which continue even in present-day psychology. hartley's association psychology refers the association processes to certain physiological conditions, while hume's regards the association process as a psychological process. The first form allies itself, accordingly, to psycho-physical materialism; this is found in the works of such a modern writer as herbert spencer. Closely related to hume's psychological associationism is the psychology of herbart. Herbart's doctrine of the statics and mechanics of ideas is a purely intellectualistic doctrine. (Feeling and volition are here recognized only as certain phases of ideas). It is in agreement with associationism in its fundamental mechanical view of mental life. This similarity is not to be overlooked merely because Herbart sought through certain hypothetical assumptions to give his psychological discussions an exact mathematical form. There are many anticipations of voluntaristic psychology in the works of psychologists of the "pure introspection" school, and of the association schools. The first thorough-going exposition of this form of psychology was the work of the author of this Outlines of Psychology in his psychological treatises. It is to be noted that this psychological voluntarism, as, indeed, one can see from the description which has already been given, is to be clearly distinguished from metaphysical voluntarism as developed by such a writer as schopenhauer. Metaphysical voluntarism seeks to reduce everything to an original transcendental will, which lies back of the phenomenal world and serves as a substratum for this world. Psychological voluntarism, on the other hand, looks upon empirical volitional processes with their constituent feelings, sensations, and ideas, as the types of all conscious processes. For such a voluntarism even volition is a complex phenomenon which owes its typical significance to this very fact that it includes in itself the different kinds of psychical elements.
 
 

References. Psychology of the inner sense: locke, An Essay concerning Human Understanding, 1690. Eduard Beneke, Psychologische Skizzen, 2 vols., 1825—1827, and Lehrbuch der Psychologie als Naturwissenschaft, 1833, 4th ed. 1877. K. Fortlage, System der Psychologie, 2 vols., 1855.

Faculty-psychology: Christian Wolff, Psychologia empirica, 1732, Psychologia rationalis, 1734; and Vernünftige Gedanken von Gott, der Welt, der Seele des Menschen etc., 1719. Tetens, Philosophische Versuche über die menschliche Natur, 1776—1777. Kant, Anthropologie, 1798 (a practical psychology, well worth reading even at this late date because of its many nice observations).

Association psychology: Hartley, Observations on Man, his Frame, his Duties, his Expectations, 1749. Priestly, Hartley's Theory of the Human Mind on the Principles of the Association of Ideas, 1775. Hume, Treatise on Human Nature, 1734 —1737; and Enquiry concerning Human Understanding, 1748. james mill, Analysis of the Phenomena of the Human Mind, 1829, later edited with notes by Alexander Bain, John Stuart Mill and others, 2nd ed. 1878. Alexander Bain, The Senses and the Intellect, 1855, 4th ed. 1894; and The Emotions and the Will, 1859, 3rd ed. 1875. Herbert Spencer, Principles of Psychology, 1855, 5th ed. 1890. herbart, Psychologie als Wissenschaft, 2 vols., 1824—1825; and (English trans. by M. K. Smith 1891) Text-book of Psychology, 1816.

Works which prepared the way for experimental psychology: lotze, Medizinische Psychologie, 1852. G. T. fechner, Elemente der Psychophysik, 2 vols., 1860.

More extended modern treatises. Of the Herbartian School: W. F. Volkmann, Lehrbuch der Psychologie, 2 vols., 4th ed., 1894. M. Lazarus, Leben der Seele in Monographien, 3 vols., 3rd ed. 1883. Of the Association School (generally with a tendency toward psycho-physical materialism): kuelpe, (English trans. by E. B. Titchener, 1901) Outlines of Psychology, 1893. Ebbinghaus, Grundzüge der Psychologie, 1st vol. only as yet, 1897—1902. ziehen, (English trans. by van liew and beyer 1899) Introduction to the Study of Physiological Psychology, 6th Ger. ed. 1902. Münsterberg, Grundzüge der Psychologie, 1st vol. only as yet, 1900. Works standing between association psychology and voluntaristic psychology: Hoeffding, (English trans. by Lowndes, 1891, from the German trans. 1887) Outlines of Psychology, 2nd Danish ed. 1893. W. jerusalem, Lehrbuch der empirischen Psychologie, 2nd ed. 1890. Works representing a form of intellectualism related in method to scholasticism: brentano, Psychologie vom empirischen Standpunkte, 1st vol. only, 1874. meinong, Psychologisch-ethische Untersuchungen zur Werttheorie, 1894; and Untersuchungen zur Gegenstandstheorie und Psychologie, 1904. Works emphasizing the independence of psychology and based on an empirical analysis of conscious processes: lipps, Grundtatsachen des Seelenlebens, 1883; and Leitfaden der Psychologie, 1903. jodl, Lehrbuch der Psychologie, 2nd ed., 1902. The same empirical analysis, and on the basis of this analysis voluntaristic psychology in the sense above described, are presented by the author of this Outlines of Psychology in his other works also, namely, Grundzüge der physiologischen Psychologie, 3 vols., 5th ed. 1902—1903 (English trans. in preparation by E. B. Titchener); and (English trans. by E. B. Creighton and E. B. Titchener, 1894) Lectures on Human and Animal Psychology, 3rd Ger. ed. 1897. Works treating chiefly of the philosophical character of fundamental psychological concepts: uphues, Psychologie des Erkennens, 1893. J. Rehmke, Lehrbuch der allgemeinen Psychologie, 1894. natorp, Einleitung in die Psychologie, 1888. American, English and French works all follow in the path of associationalism. Furthermore, they tend for the most part toward psycho-physical materialism or toward dualistic spiritualism, less frequently toward voluntarism. From among the numerous American works, the following are to be mentioned: james, Principles of Psychology, 2 vols., 1890. ladd, Psychology Descriptive and Explanatory, 1894. Baldwin, Handbook of Psychology, 1889. scripture, The New Psychology, 1897. Titchener, An Outline of Psychology, 1896. French works are as follows: ribot's monographs on various psychological subjects are to be mentioned. (All translated into English: Attention, The Diseases of Memory, The Diseases of the Will, The Diseases of Personality, General Ideas, The Creative Imagination). Also, the works of FOUILLÉE, which are related to German voluntarism, but contain at the same time a great deal of metaphysics and are somewhat influenced by the Platonic doctrine of ideas (L'evolutionismc des idées-forces, 1890, and Psychologie des idées-forces, 1893).

Works on the history of psychology especially worthy of mention: Siebeck, Geschichte der Psychologie, Pt. 1st, 1880 —1884, and also articles in the first three vols. of Arch. f. Gesch. d. Phil. (these cover the ancient and medieval periods). lange, History of Materialism. dessoir, Geschichte der neueren deutschen Psychologie, 2nd ed. 1902 (including as yet only 1st vol.). sommer, Grundzüge einer Geschichte der deutschen Psychologie und Aesthetik von Wolf-Baumgarten bis Kant-Schiller, 1892. ribot, (English trans. by Baldwin) German Psychology of Today, Fr. ed. 1885, Eng. ed. 1886. W. Wundt, "Psychologie" in the Festschrift for Kuno Fischer, 1904.