Our standpoint is that of the Aristotelian and Scholastic Philosophy; but, being imbued with a thoroughly peripatetic spirit, we desire to keep in constant touch with contemporary science and thought. The Middle Ages excelled in reflecting upon general truths. Modern inquirers are wonderfully equipped for the work of analysis, and bring thereto as much patience as sagacity. Is it not evidently the proper task of a time-honoured philosophy desirous of renewing its youth in the world of to-day to bring the wisdom of past ages to bear upon the latest triumphs of science and doctrines now accepted? And if this task is faithfully discharged, may not a real advance be legitimately anticipated? Among the various reviews of what we have already published is one which we desire to quote, because it bears witness to the fact that the NeoThomist aim has been correctly appreciated in the scientific circles from which it comes. It appeared in M. Richet's Revue scientifique. "This work"-our treatise on Psychology-" is well worth pointing out to those who have given up official Spiritualism and who are looking for a philosophy which may be reconciled with science. " The Neo-Thomist school has renewed the youth of Scholastic teaching by becoming thoroughly imbued with the peripatetic spirit. It abandons all the doctrines that were founded upon a too scanty knowledge of nature, and it takes full advantage of modern discoveries, studying them according to the method of Aristotle. "So great is the vitality of this philosophy that it finds a place in its scheme for the contemporary researches of physiology and psychophysics without compromising any principle, and without ever misrepresenting science, as is constantly done in standard books. Far from dreading physiological investigation it regrets that its studies on the nervous system, mental localization, and the senses, have not been carried further, for in them it recognizes indispensable auxiliaries. M. Mercier congratulates the pioneers of physiological psychology on restoring traditions which had been broken by an interval of many centuries." The present treatise is specially addressed to those who are no longer satisfied with the standard spiritualism, and if amidst the swarm of systems and growing crowd of facts that are around them they are in search of some guiding principle of thought, they may perhaps be able to take advantage of the comparison we shall endeavour to make between the psychology of Descartes, the chief founder of the official spiritualism, and the anthropology of Aristotle and the Middle Ages. Chapter I is devoted to an examination of the psychology of the great French innovator. In it we shall deal first with his exaggerated spiritualistic theory, and then with his mechanical theory as applied to the study of man. Chapter II aims at determining the historical evolution of the Cartesian psychology, and we do this according to the scheme laid down in Chapter I, examining, first, the evolution of spiritualism (Art. I), which gives rise to Occasionalism, Spinozism, Ontologism (Sect. I), and Idealism (Sect. II); next, the evolution of the mechanical theory (Art. II).