That would have been, indeed, the one fundamental mistake, as the whole Congress work was planned in the service of the great synthetic movement which pervades the intellectual life of to-day. The undertaking would be useless and even hindering if it were not just the newer and deeper tendencies that came to most complete expression in it. Everything depended, therefore, upon the fullest possible representation of scientific endeavors in the plan. But no one can become aware of this manifoldness and of the logical relations who does not go back to the ultimate principles of the human search for truth. We have, therefore, to enter now into a full discussion of the principles which have controlled the classification and subdivision of the whole work. The discussion is necessarily in its essence a philosophical one, as it was earlier made plain that philosophy must lay out the plan, while in the realization of the plan through concrete work the scientist alone, and not the logician, has to speak. Yet here again it may be said that while our discussion of principles in its essence is logical, in another respect it is a merely historical account. The question is not what principles of classification are to be acknowledged as valuable now that the work of the Congress lies behind us, but what principles were accepted and really led to the organization of the work in that form in which it presents itself in the records of the following volumes.
II
THE CLASSIFICATION OF THE SCIENCES
1. The Development of Classification
The problem of dividing and subdividing the whole of human knowledge and of thus bringing order into the manifoldness of scientific efforts has fascinated the leading thinkers of all ages. It may often be difficult to say how far the new principles of classification themselves open the way for new scientific progress and how far the great forward movements of thought in the special sciences have in turn influenced the principles of classification. In any case every productive age has demanded the expression of its deepest energy in a new ordering of human science. The history of these efforts leads from Plato and Aristotle to Bacon and Locke, to Bentham and Ampère, to Kant and Hegel, to Comte and Spencer, to Wundt and Windelband. And yet we can hardly speak of a real historical continuity. In a certain way every period took up the problem anew, and the new aspects resulted not only from the development of the sciences themselves which were to be classified, but still more from the differences of logical interest. Sometimes the classification referred to the material, sometimes to the method of treatment, sometimes to the mental energies involved, and sometimes to the ends to be reached. The reference to the mental faculties was certainly the earliest method of bringing order into human knowledge, for the distinction of the Platonic philosophy between dialectics, physics, and ethics pointed to the threefold character of the mind, to reason, perception, and desire; and it was on the threshold of the modern time, again, when Bacon divided the intellectual globe into three large parts according to three fundamental psychical faculties: memory, imagination, and reason. The memory gives us history; the imagination, poetry; the reason, philosophy, or the sciences. History was further divided into natural and civil history; natural history into normal, abnormal, and artificial phenomena; civil history into political, literary, and ecclesiastical history. The field of reason was subdivided into man, nature, and God; the domain of man gives, first, civil philosophy, parted off into intercourse, business, and government, and secondly, the philosophy of humanity, divided into that of body and of soul, wherein medicine and athletics belong to the body, logic and ethics to the soul. Nature, on the other hand, was divided into speculative and applied science,—the speculative containing both physics and metaphysics; the applied, mechanics and magic. All this was full of artificial constructions, and yet still more marked by deep insight into the needs of Bacon's time, and not every modification of later classifiers was logically a step forward.
Yet modern efforts had to seek quite different methods, and the energies which have been most effective for the ordering of knowledge in the last decades spring unquestionably from the system of Comte and his successors. He did not aim at a system of ramifications; his problem was to show how the fundamental sciences depend on each other. A series was to be constructed in which each member should presuppose the foregoing. The result was a simplicity which is certainly tempting, but this simplicity was reached only by an artificial emphasis which corresponded completely to the one-sidedness of naturalistic thought. It was a philosophy of positivism, the background for the gigantic work of natural science and technique in the last two thirds of the nineteenth century. Comte's fundamental thought is that the science of Morals, in which we study human nature for the government of human life, is dependent on sociology. Sociology, however, depends on biology; this on chemistry; this on physics; this on astronomy; and this finally on mathematics. In this way, all mental and moral sciences, history and philology, jurisprudence and theology, economics and politics, are considered as sociological phenomena, as dealing with functions of the human being. But as man is a living organism, and thus certainly falls under biology, all the branches of knowledge from history to ethics, from jurisprudence to æsthetics, can be nothing but subdivisions of biology. The living organism, on the other hand, is merely one type of the physical bodies on earth, and biology is thus itself merely a department of physics. But as the earthly bodies are merely a part of the cosmic totality, physics is thus a part of astronomy; and as the whole universe is controlled by mathematical laws, mathematics must be superordinated to all sciences.
But there followed a time which overcame this thinly disguised example of materialism. It was a time when the categories of the physiologist lost slightly in credit and the categories of the psychologist won repute. This newer movement held that it is artificial to consider ethical and logical life, historic and legal action, literary and religious emotions, merely as physiological functions of the living organism. The mental life, however necessarily connected with brain processes, has a positive reality of its own. The psychical facts represent a world of phenomena which in its nature is absolutely different from that of material phenomena, and, while it is true that every ethical action and every logical thought can, from the standpoint of the biologist, be considered as a property of matter, it is not less true that the sciences of mental phenomena, considered impartially, form a sphere of knowledge closed in itself, and must thus be coördinated, not subordinated, to the knowledge of the physical world. We should say thus: all knowledge falls into two classes, the physical sciences and the mental sciences. In the circle of physical sciences we have the general sciences, like physics and chemistry, the particular sciences of special objects, like astronomy, geology, mineralogy, biology, and the formal sciences, like mathematics. In the circle of mental sciences we have correspondingly, as a general science, psychology, and as the particular sciences all those special mental and moral sciences which deal with man's inner life, like history or jurisprudence, logic or ethics, and all the rest. Such a classification, which had its philosophical defenders about twenty years ago, penetrated the popular thought as fully as the positivism of the foregoing generation, and was certainly superior to its materialistic forerunner.
Of course it was not the first time in the history of civilization that materialism was replaced by dualism, that biologism was replaced by psychologism; and it was also not the first time that the development of civilization led again beyond this point: that is, led beyond the psychologizing period. There is no doubt that our time presses on, with all its powerful internal energies, away from this Weltanschauung of yesterday. The materialism was anti-philosophic, the psychological dualism was unphilosophic. To-day the philosophical movement has set in. The one-sidedness of the nineteenth century creed is felt in the deeper thought all over the world: popular movements and scholarly efforts alike show the signs of a coming idealism, which has something better and deeper to say than merely that our life is a series of causal phenomena. Our time longs for a new interpretation of reality; from the depths of every science wherein for decades philosophizing was despised, the best scholars turn again to a discussion of fundamental conceptions and general principles. Historical thinking begins again to take the leadership which for half a century belonged to naturalistic thinking; specialistic research demands increasingly from day to day the readjustment toward higher unities, and the technical progress which charmed the world becomes more and more simply a factor in an ideal progress. The appearance of this unifying congress itself is merely one of a thousand symptoms of this change appearing in our public life, and if the scientific philosophy is producing to-day book upon book to prove that the world of phenomena must be supplemented by the world of values, that description must yield to interpretation, and that explanation must be harmonized with appreciation: it is but echoing in technical terms the one great emotion of our time.
This certainly does not mean that any step of the gigantic materialistic, technical, and psychological development will be reversed, or that progress in any one of these directions ought to cease. On the contrary, no time was ever more ready to put its immense energies into the service of naturalistic work; but it does mean that our time recognizes the one-sidedness of these movements, recognizes that they belong only to one aspect of reality, and that another aspect is possible; yes, that the other aspect is that of our immediate life, with its purposes and its ideals, its historical relations and its logical aims. The claim of materialism, that all psychical facts are merely functions of the organism, was no argument against psychology, because, though the biological view was possible, yet the other aspect is certainly a necessary supplement. In the same way it is no argument against the newer view that all purposes and ideals, all historical actions and logical thoughts, can be considered as psychological phenomena. Of course we can consider them as such, and we must go on doing so in the service of the psychological and sociological sciences; but we ought not to imagine that we have expressed and understood the real character of our historical or moral, our logical or religious life when we have described and explained it as a series of phenomena. Its immediate reality expresses itself above all in the fact that it has a meaning, that it is a purpose which we want to understand, not by considering its causes and effects, but by interpreting its aims and appreciating its ideals.
We should say, therefore, to-day that it is most interesting and important for the scientist to consider human life with all its strivings and creations from a biological, psychological, sociological point of view; that is, to consider it as a system of causal phenomena; and many problems worthy of the highest energies have still to be solved in these sciences. But that which the jurist or the theologian, the student of art or of history, of literature or of politics, of education or of morality, is dealing with, refers to the other aspect in which inner life is not a phenomenon but a system of purposes, not to be explained but to be interpreted, to be approached not by causal but by teleological methods. In this case the historical sciences are no longer sub-sections of psychological or of sociological sciences; the conception of science is no longer identical with the conception of the science of phenomena. There exist sciences which do not deal with the description or explanation of phenomena at all, but with the internal relation and connection, the interpretation and appreciation of purpose. In this way modern thought demands that sciences of purpose be coördinated with sciences of phenomena. Only if all these tendencies of our time are fully acknowledged can the outer framework of our classification offer a fair field to every scientific thought, while a positivistic system would cripple the most promising tendencies of the twentieth century.