present work we have devoted Book I. mainly to Empirical Psychology, whilst Book II. is confined to the problems of Rational Psychology. We have not, however, sought to make the division rigid: in fact, our chief contention is that a complete and accurate separation of the two branches of Psychology is impossible. Thus we have included in our First Book certain questions regarding external perception, memory, the origin of ideas, the nature of intellectual activity, and the freedom of the will which would now-a-days be usually allotted to the sphere of Rational Psychology. The two branches of the science of course employ both observation and inference; but while frequent appeal to the facts of consciousness is a prominent feature in the first stage, deductive reasoning prevails in the last. Starting from the knowledge acquired in Empirical Psychology regarding the character of the operations and activities of the mind, we draw further conclusions as to the nature and constitution of the root or subject of these activities. The knowledge of the effect leads us up to that of the cause; the mode of action indicates the nature of the agent. We may thus hope by a judiciously combined use of reasoning and observation to attain to a well grounded assurance regarding the existence of an immaterial soul, its relations with the body, its origin, and its future destiny.

The scope of Psychology will be made still clearer by pointing out how it is connected with other kindred sciences, and how it is separated from them. In the scheme of strictly metaphysical

branches of speculation it stands opposed to Cosmology, as the Philosophy of spirit to that of nature. The latter science seeks to investigate the inner constitution of matter, the nature of space and time, and the ultimate principles or laws which underlie and govern the course of the universe; while Psychology confines itself to the study of the subjective world, the mind of man. There are, however, other departments of Philosophical knowledge of a subjective character; both Logic and Ethics deal with mental activities. As regards Rational Psychology, which inquires into the nature of the mind itself, there is no difficulty in seeing how it is differentiated from these sciences, so we need only keep Empirical Psychology in view when comparing them. Both Psychology and Logic study mental states, but whereas the former embraces within its ken sensations, emotions, volitions, and all other classes of conscious acts, the latter is limited to the consideration of cognitive operations, and mainly to that of reasoning. Again, the points of view from which they approach their subjectmatter is different. Psychology looks on our mental processes as natural events interesting in themselves. It seeks to describe and classify them, to explain their genesis, and to discover their laws. or constant modes of action. It may, indeed, incidentally afford useful information regarding the acquisition of habits, the cultivation of the memory, and the training of other faculties; but its primary aim is speculative. Logic, on the other hand, is interested in mental operations as representative of

In a

objective fact. It is the science, not of thinking in general, but of correct thinking. It is less purely a speculative science, and in the eyes of some even its primary aim is practical. Its object is the discovery of the general canons of truth. It is, in the words of St. Thomas, "the science which teaches man how to order aright the acts of the intellect in the pursuit and attainment of truth." word, while Psychology studies thought merely as a subject, Logic investigates it for an object. The researches of the psychologist are directed towards the causal connections between mental states, and lead up to the apprehension of a body of natural laws-general truths describing uniformities of succession and co-existence among such states. Those of the logician centre upon the rational correlations of intellectual aets, and result in the formulation of a code of normal laws-a body of precepts-which can be disobeyed but under the penalty of error. In addition to these points of similarity and contrast, the two sciences are related by a certain mutual interdependence. Psychology, like every other science, must conform to the rules of right reasoning; it must observe the canons of inductive and deductive inference, and it must carry out the general precepts of Logical Method. On the other hand, the validity of thought may seriously affected by its genesis. The materials with which the logician works are products which have been analyzed by the psychologist, and, consequently, although Logic is not properly based on Psychology, a false theory of the nature of our

be

cognitive faculties may sap the very foundations of knowledge, and lead to a disbelief in the existence of all real truth. Logic may therefore at times have to appeal to a sound system of Psychology in justification of its fundamental assumptions.

It

Ethics as the science of morality is easily distinguished from Psychology. It investigates the right end of human action, the nature and foundations of moral distinctions, the grounds of moral obligation, and the sanctions of morality. classifies virtues, vices, and duties, and promulgates the rules of right conduct. Whereas Psychology considers our mental activities in their causes, Ethics studies them in their results: and while Logic seeks to harmonize cognition with the order of the physical world-the Real; Ethics would conform volition to the order of the moral worldthe Ideal. In establishing, however, the existence of moral intuitions, and in exhibiting their character, appeal must be made to the philosophy of the mind. The nature of the mental activity called conscience, the genesis of moral sentiments, the formation of moral habits, and the freedom of the will, a truth on the proof of which moral responsibility in its universally accepted sense is absolutely dependent; all these questions-matters of the highest importance to the moral philosopherbelong to the sphere of Psychology.

5 We have noticed only the most striking points of contrast. Strictly speaking, Logic is concerned for all truth-physical, metaphysical, and moral. For a complete account of the province of Logic, cf. Logic, by R. F. Clarke, S.J. c. i. On the question how far Logic is to have allotted to it a practical aim, cf. id. pp. 19-25.

6

The term Biology is sometimes used in a wide sense to embrace all the branches of knowledge which treat of the phenomena of life. More properly, it comprehends two co-ordinate physical sciences, Morphology, which investigates the structures of living organisms, and Physiology, which investigates their functions. The latter science stands in close relations to Psychology, both Phenomenal and Rational. The physiologist studies the various operations of our vegetative life, he examines into the action of digestion, respiration, growth, nutrition, and the other vital processes which take place within us. He observes the working of our several organs, and seeks to enunciate laws that will express the general uniformities exhibited in the aggregate of operations which go to constitute our physical life. These events are perceived by the external senses, and are ultimately reducible to movements in matter. Physiology is thus distinguished from Empirical Psychology, both by the phenomena of which it treats, and by the faculty through which these phenomena are apprehended. It is marked off on the other hand from Rational

The term positive science is frequently used to designate those branches of knowledge which deal with the laws of phenomena, facts observable by immediate experience. Some writers would confine the term science exclusively to this signification. Such usage is, however, illegitimate. The object of science is to discover causation; consequently, the inquiry into primary causes, which are properly the real causes, has a fortiori a right to this title. For the sake of precision, however, the term philosophical science may be conveniently employed to denote those branches of knowledge which deal not merely with secondary, but with the higher or primary causes. Rational Psychology is in this sense a philosophical science, as compared with the phenomenalistic or so-called positive sciences of Physiology and Empirical Psychology.