of exceptional length, and also of progress which, though slow, has been continuous and steady in the main; the nature of its subject-matter explaining at once how the progress has not been faster, and how it was so early begun. Yet, early constituted as it was, the science of mind was by no means the first achievement of human intellect on awaking to reflection. Two centuries of strenuous thought passed before mind was so distinctly conceived, as to become, with Plato, the subject of special inquiry. The aboriginal dualistic conception of soul as a separable entity spread somehow through the body was there, lingering on for future transformation, but at first it was quite submerged by the thought of finding one universal expression for the whole variety of human experience, which had now been taken into view. A "hylozoic monism," without distinction of mind, or even of life, from other change in things, was the earliest express theory of the universe as a whole. Only when, still keeping in view the need for a comprehensive theory, successive thinkers became struck with this or that aspect of being as more important than others, and in particular awoke, however partially, to contemplation on the facts of subjective experience, and were faced by the contradictions of sense and cognition, did the primitive dualism begin to re-assert itself with new fulness of meaning as the true account of human nature; not without help, as already suggested, from the lights afforded by medical practice. All this is worked out, at adequate length and with great clearness of insight, by Prof. Siebeck. When he passes to Plato, through the Sophists and Socrates, in both of whom, to whatever different purpose, the subjective attitude necessary for psychological science is seen to be decisively gained, he finds it necessary to enlarge to an extent only less than afterwards as regards Aristotle. In Plato the rehabilitated dualism of natural fancy becomes metaphysically theorised with an ethical purpose, yet so as to give occasion for a detailed survey of the whole range of mental life such as no one (at least in the West) had ever undertaken before. None of the phases of human activity, theoretic or practical, remain any longer in shadow; and there is left for Aristotle only the task of re-investigation from a more disinterested point of view-in the spirit of science rather than with reference to a moral and religious ideal. How this was carried through we may here bes indicate, not by any attempt to examine Prof. Siebeck's admirable exposition of the Aristotelian doctrine or his view of its strength and its shortcomings, but as we follow his account of the later psychology, and note with him the long-protracted efforts made by professed adherents to understand and develop, or by others to modify and supplement, the scientific scheme with which all had henceforth to reckon.

Two general movements are distinguished by the historian within the time while as yet the Greek (or Græco-Roman) mind

had not become dominated-though towards the end it was largely affected-by religious ideas of Oriental, chiefly Hebrew, origin: (1) a complex and highly-diversified movement of "monistic naturalism", which evoked (2) a sharply marked "spiritualistic reaction. The first rubric is intended to cover the Stoic and the Epicurean as well as the Peripatetic psychology, with the notable contribution made by Galen and other physiologists engaged in medical practice. Upon this movement as a whole (if it may be called one movement), Prof. Siebeck is constrained at the end to write the word failure; though the observations he records as made within the period, in the series of well-ordered chapters, so brimful of matter, occupying pp. 128-296, may not seldom incline the reader to demur to his depreciatory estimate. It is certainly impossible not to be struck with the advance then made beyond Aristotle, at a multitude of points, towards the accepted positions of later psychological science. If, outside mathematics, there was any progress being made in scientific knowledge, it was mainly in the psychological field. Yet Prof. Siebeck is doubtless justified in asserting that Aristotle's naturalistic successors failed to maintain the inquiry at the level to which he had raised it. When they did effective work, it was by following the lead he had given; and in general they were far from comprehending the profounder (philosophical) ideas that had enabled him to bring mind into line with other subjects of scientific inquiry or even give it scientific treatment in advance of the others. In particular, the conception of man as an organic unity, whereby he was able to give a "real" explanation (in physiological terms) of mental processes and functions-short, it is true, of the highest-while maintaining the independence of their subjective character and reserving their philosophical import, was with difficulty kept by his Peripatetic followers from passing, and often did pass, into an assertion of mere materialism. Epicureans and Stoics, on the other hand, never either of them attained to the height of the conception, but each, in their different ways, secured a real ground of explanation at the sacrifice, generally, of the more distinctive characteristics of mental life.

It is to help in threading his way through the complex tangle of Post-Aristolelian inquiry that Prof. Siebeck finds it expedient, or necessary, to follow out separately, in a preliminary chapter, the history of the notion Pneuma; incorporating, in somewhat reduced form, a research he had previously published in the Zeitschrift für Völkerpsychologie u. Sprachwissenschaft xii. 4. From being employed originally, in the sense of air or warm vapour, to designate the inner active principle in man regarded as made up of two extended entities, soul and body, one within the other, Pneuma comes in course of time to be understood as soul in a sense exclusive of all material attribution and more especially, from the religious point of view, as the element in human nature

setting man in felt relation with Deity. But while soul, under whatever name, is becoming conceived antithetically to body in every respect except in that of real existence, Pneuma tends also to acquire the other import of intermediary between the two opposite terms. The primitive crude dualism thus passes into a trinalism of human nature, not only for Christian teachers and for such metaphysical thinkers as join to supreme concern for an ethical or religious purpose an interest in theoretic explanation. Scientific inquirers also, who start from no definite metaphysical position, are seen to be moved in the like direction of interpreting subjective mental experience, once brought distinctly within ken, as proceeding in connexion with bodily changes through a special agency called Vital or Animal Spirit. To all such, Pneuma, in its original sense of an attenuated matter like air or vapour, offers itself as exactly the mean term that is wanted. Material like the body into which it enters and out of which it passes, it is by its invisibility and rarity akin to whatever can be thought of as opposed to gross material substance and thus to mind or soul subjectively apprehended. Especially will this consideration impress itself upon physiological inquirers, who, as they learn more and more of the detail of vital processes among which respiration stands foremost, have the task of understanding the bodily life in connexion with the mental life so intimately blended with it. It is thus that Galen and his medical fore-runners and successors acquire a peculiar importance in the history of psychological theory. Recognising, as Aristotle did not, the special relation in which the nervous system stands to mind, they elaborated a theory of nerve-action by means of "animal spirits" which, however erroneous from their failure (though distinguishing between arteries and veins) to anticipate Harvey's revolutionary discovery, served to give a truer representation than Aristotle's of the actual physical basis of mental processes and has left abiding traces in common speech. Aristotle himself did not, in his physiology, wholly dispense with the agency of Pneuma in the sense of animal heat; but, besides the physiologists, it was the Stoics who most persistently took advantage of its ambiguous character and, while freely using it as a physical agent wherever called for, sought also to express by means of it not only the being and activity of mind but also the abstract qualities of things through which they become the subject of thought. The notion, in short, is one that, as it is employed, gives the measure, at every stage, of the advance made, on the one hand, in power of abstract conception and, on the other, in determination to keep the realm of properly subjective experience, as it gradually opens up and deepens, in relation with the common ground of physical experience upon which men meet and from which all their inquiry starts. But the final transformation, as Prof. Siebeck shows, which it underwent before it became fitted to serve the purposes of the spiritualistic reaction against naturalism that closed the movement of Pagan

thought in antiquity, as also the wants of upcoming Christianity, was operated through Hebrew influence. While the Hebrew mind had also started with a physical conception of the active principle of human nature, corresponding to the original sense of Pneuma, it had always viewed this principle as divine in its origin and as a bond between creature and Creator. It is interesting then to note that in the Alexandrian Jew Philo the two currents of Greek thought and Hebrew feeling first come manifestly together, and, as it happens, Philo uses the word Pneuma at different places in such a variety of senses, early and late, that the whole development of the notion can be traced within his writings.

The other notion, of Consciousness, treated apart by the author does not accomplish its development till the next period, when the spiritualistic reaction of the Neo-Platonist school had set in. In the section (pp. 297-357) given to this movement of reversion from Aristotle to Plato, its causes and general character are first set out before the psychological advance, for which the school has not received sufficient credit, is chronicled. The advance, due chiefly to Plotinus, does not consist only in the explicit recognition of what is involved in the notion of Consciousness, but this may be singled out (as by Prof. Siebeck in his special chapter) for particular notice because of its critical importance. That the notion should first have been apprehended in its full import by thinkers who were revolting, under ethical and religious motives, from a naturalism that had passed into materialism and who were ready to sacrifice everything for the restored sense of inwardness, is not surprising. The earlier revulsion of Socrates from a less developed form of naturalism, though similarly motived, led to no such thoroughgoing assertion of conscious antithesis of mind to nature as was now wrung from the Neo-Platonist puritans. Accordingly Plato and Aristotle, in spite of their developed psychology, have no general word to mark the attitude of the introspective observer, nor do they clearly recognise that synthetic activity which is the note of conscious mind alike for psychologist and philosopher. The fundamental deficiency was not likely to be made good in the following period when no advance, but rather the reverse, was made in general philosophical conception. Nevertheless when the time came for protest against the PostAristotelian naturalism, Plotinus and the Neo-Platonists had the benefit of the increase of insight that had meanwhile been gained into the details of psychical experience. In Galen and several of the Stoics as well as Peripatetics, may be noted a distinct approach towards the various expressions in which Plotinus was able at last to characterise effectively the attitude of subjective reflection upon the whole round of experience. The significance of the step lies in the fact that without such a conception of Consciousness as was then first attained (though not therefore immediately or indeed for long afterwards utilised), it is impossible to bring into

view the phenomenal opposition of mind and things with which the scientific psychologist has to work.

The final section, devoted to the Christian rendering of ancient psychology, though it ranges over many centuries, from the second to the thirteenth, occupies not much more than 100 pp., for the good reason because there was no scientific advance through all that time to compare with what had been made within two or three centuries before. At first, Christian thought turned mainly upon the question of the nature of the soul, and, under the exigencies of appeal to the popular imagination in regard to a future life, there was a distinct recrudesence of the old materialistic dualism; until Augustin restored the cause of philosophic spiritualism while asserting the duality of men's nature, and fixed the main lines of orthodox animism from that time forth. But Augustin was also, in the more special sense, a psychologist of mark-the one original inquirer in the Patristic period, and his observations (on belief in relation to knowledge, on will and other mental processes), though always having a confessional motive, are such as to deserve all the attention that Prof. Siebeck accords them (pp. 381-97). In the Scholastic period, after an account of some more or less independent tentatives to develop psychological schemes in accordance with Christian needs-which, in as far as they were not independent, took colour from Plato-the historian has to note (in customary fashion) the gradual soaking-in of Aristotelian influence from the 12th to the 13th century. When the saturation of the medieval mind had become complete, he takes perhaps the most effective way of appreciating the result-in a detailed exposition of the psychological system of Thomas (pp. 448-72).

How far all the various lines of Scholastic activity are brought sufficiently into view cannot be judged till in his next volume Prof. Siebeck traces those other currents within the Middle Age which are the true beginning, so far back, of the Modern movement in psychology. At present some thinkers are passed over, as Anselm and Abælard, who, though they may afterwards be noticed in connexion with the Nominalistic theory which they differently opposed, might have had their places assigned in the general development as thus far indicated. But, however this may be, nothing but thanks is due for the instructive presentation of the Aristotelian psychology in its Christian guise. The large comprehensiveness of the original doctrine, which brought mind into relation with life in general, was not lost upon such an intellect as that of Thomas; giving his psychological thought that disposition which enables the revived Scholasticism of these days-revived or at least re-awakened to militancy-still to present some kind of front to the most recent advances of science. Nor had the Christian discipline failed to direct attention to aspects of mental life which Aristotle had overlooked; so that now they received, upon Aristotelian lines, a systematic consideration as never before.