Historical Use of the Term.— 'The most helpful introduction to such a task is afforded by a survey of the steps by which philosophy differentiated itself, in the history of Greek thought, from the idea of knowledge and culture in general. These steps may be traced in the gradual specification of the term. The tradition which assigns the first employment of the word to Pythagoras has hardly any claim to be regarded as authentic; and the somewhat self-conscious modesty to which Diogenes Laertius attributes the choice of the designation is, in all probability, a piece of etymology crystallized into narrative. It is true that, as a matter of fact, the earliest uses of the word (the verb φιλοσοφεω occurs in Herodotus and Thucydides) imply the idea of the pursuit of knowledge; but the distinction between the σοφός, or wise man, and the φιλόσοφος, or lover of wisdom, appears first in the Platonic writings, and lends itself naturally to the so-called Socratic irony. The same thought is to be found in Xenophon, and is doubtless to be attributed to the historical Socrates. But the word soon lost this special implication. What is of real interest to us is to trace the progress from the idea of the philosopher as occupied with any and every department of knowledge to that which assigns him a special kind of knowledge as his province. A specific sense of the word first meets us in Plato, who defines the philosopher as one who apprehends the essence or reality of things in opposition to the man who dwells in appearances and the shows of sense. The philosophers, he says, “are those who are able to grasp the eternal and immutable”; they are “those who set their affections on that which in each case really exists” (Rep., 480). In Plato, however, this distinction is applied chiefly in an ethical and religious direction; and, while it defines philosophy, so far correctly, as the endeavour to express what things are in their ultimate constitution, it is not yet accompanied by a sufficient differentiation of the subsidiary inquiries by which this ultimate question may be approached. Logic, ethics, and physics, psychology, theory of knowledge, and metaphysics are all fused together by Plato in a semi-religious synthesis. It is not till we come to Aristotle—the encyclopaedist of the ancient world— that we find a demarcation of the different philosophic disciplines corresponding, in the main, to that still current. The earliest philosophers, or “physiologers,” had occupied themselves chiefly with what we may call cosmology; the one question which covers everything for them is that of the underlying substance of the world around them, and they essay to answer this question, so to speak, by simple inspection. In Socrates and Plato, on the other hand, the start is made from a consideration of man’s moral and intellectual activity; but knowledge and action are confused with one another, as in the Socratic doctrine that virtue is knowledge. To this correspond the Platonic confusion of logic and ethics and the attempt to substitute a theory of concepts for a metaphysic of reality. Aristotle’s methodic intellect led him to separate the different aspects of reality here confounded. He became the founder of logic, psychology, ethics, and aesthetics as separate sciences; while he prefixed to all such (comparatively) £ )ecial inquiries the investigation of the ultimate nature of existence as such, or of those first principles which are common to, and presupposed in, every narrower field of knowledge. For this investigation Aristotle’s most usual name is “first philosophy”; but there has since been appropriated to it, apparently by accident, the title “metaphysics.” “Philosophy,” as a term of general application, was not, indeed, restricted by Aristotle or his successors to the disciplines just enumerated. Aristotle himself includes under the title, besides mathematics, all his physical inquiries. It was only in the Alexandrian period, as Zeller points out, that the special sciences attained to independent cultivation. Nevertheless, as the mass of knowledge accumulated, it naturally came about that the name “philosophy” ceased to be applied to inquiries concerned with the particulars as such. The details of physics, for example, were abandoned to the scientific specialist, and philosophy restricted itself in this department to the question of the relation of the physical universe to the ultimate ground or author of things. This inquiry, which was long called “rational cosmology,” may be said to form part of the general science of metaphysics, or at all events a pendant to it. By the gradual sifting out of the special sciences philosophy thus came to embrace primarily the inquiries grouped as “metaphysics” or “first philosophy.” These would embrace, according to the scheme long current, ontology proper, or the science of being as such, with its branch sciences of (rational) psychology, cosmology, and (rational or natural) theology. Subsidiary to metaphysics, as the central inquiry, stand the sciences of logic and ethics, to which may be added aesthetics, constituting three normative sciences, —sciences, that is, which do not, primarily, describe facts, but rather prescribe ends. It is evident, however, that if logic deals with conceptions which may be considered constitutive of knowledge as such, and if ethics deals with the harmonious realization of the highest known form of existence, both sciences must have a great deal of weight in the settling of the general question of metaphysics.

Modern modifications of the above scheme will be presently considered; but it is sufficiently accurate as a storting-point, and its acceptance by so many generations of thinkers is a guarantee for its provisional intelligibility. Accordingly, we may say that “philosophy” has been understood, during the greater part of its history, to be a general term covering the various disciplines just enumerated. It has frequently tended, however, and still tends, to be used as specially convertible with the narrower term “metaphysics.” This is not unnatural, seeing that it is only so far as they bear on the one central question of the nature of existence that philosophy spreads its mantle over psychology, logic, or ethics. The organic conditions of perception and the associative laws to which the mind, as a part of nature, is subjected, are nothing to the philosopher; and therefore the handing over of (empirical) psychology to special investigators, which is at present taking place, can be productive of none but good results. Similarly, logic, so far as it is an art of thought or a doctrine of fallacies, and ethics, so far as it is occupied with a natural history of impulses and moral sentiments, do neither of them belong, except by courtesy, to the philosophic province. But, although this is so, it is perhaps hardly desirable to deprive ourselves of the use of two terms instead of one. It will not be easy to infuse into so abstract and bloodless a term as “metaphysics” the fuller life (and especially the inclusion of ethical considerations) suggested by the more concrete term “philosophy.”

We shall first of all, then, attempt to differentiate philosophy from the special sciences, and afterwards proceed to take up one by one what have been called the philosophical sciences, with the view of showing how far the usual subject-matter of each is really philosophical in its bearing, and how far it belongs rather to the domain of science strictly so called. We shall also see in the course of this inquiry in what these various philosophical disciplines differ from one another, and how far they merge into another, or have, as a matter of fact, been confused at different periods in the history of philosophy. The order in which, for clearness of exposition, it will 'be most convenient to consider these disciplines will be psychology, epistemology or theory of knowledge, and metaphysics, then logic, aesthetics, and ethics. Finally, the connexion of the last-mentioned with politics (or, to speak more modernly, with jurisprudence and sociology) and with the philosophy of history will call for a few words on the relation of these sciences to general philosophy.

Philosophy and Science.— In distinguishing philosophy from the sciences, it may not be amiss at the outset to guard against the possible misunderstanding that philosophy is concerned with a subject-matter different from, and in some obscure way transcending, the subject-matter of the sciences. Now that psychology, or the observational and experimental study of mind, may be said to have been definitively included among the positive sciences, there is not even the apparent ground which once existed for such an idea. Philosophy, even under its most discredited name of metaphysics, has no other subject-matter than the nature of the real world, as that world lies around us in everyday life, and lies open to observers on every side. But if this is so, it may be asked what function can remain for philosophy when every portion of the field is already lotted out and enclosed by specialists? Philosophy claims to be the science of the whole; but, if we get the knowledge of the parts from the different sciences, what is there left for philosophy to tell us? To this it is sufficient to answer generally that the synthesis of the parts is something more than that detailed knowledge of the parts in separation which is gained by the man of science. It is with the ultimate synthesis that philosophy concerns itself; it has to show that the subject-matter which λve are all dealing with in detail really is a whole, consisting of articulated members. Evidently, therefore, the relation existing between philosophy and the sciences will be, to some extent, one of reciprocal influence. The sciences may be said to furnish philosophy with its matter, but philosophical criticism reacts upon the matter thus furnished, and transforms it. Such transformation is inevitable, for the parts only exist and can only be fully, i.e., truly, known in their relation to the whole. A pure specialist, if such a being were possible, would be merely an instrument whose results had to be co-ordinated and used by others. Now, though a pure specialist may be an abstraction of the mind, the tendency of specialists in any department naturally is to lose sight of the whole in attention to the particular categories or modes of nature’s working which happen to be exemplified, and fruitfully applied, in their own sphere of investigation; and in proportion as this is the case it becomes necessary for their theories to be co-ordinated with the results of other inquirers, and set, as it were, in the light of the whole. This task of co-ordination, in the broadest sense, is undertaken by philosophy; for the philosopher is essentially what Plato, in a happy moment, styled him, συνοπτικός, the man who insists on seeing things together. The aim of philosophy (whether attainable or not) is to exhibit the universe as a rational system in the harmony of all its parts; and accordingly the philosopher refuses to consider the parts out of their relation to the whole whose parts they are. Philosophy corrects in this way the abstractions which are inevitably made by the scientific specialist, and may claim, therefore, to be the only concrete science, that is to say, the only science which takes account of all the elements in the problem, and the only science whose results can claim to be true in more than a provisional sense.

For it is evident from what has been said that the way in which we commonly speak of “facts” is calculated to convey a false impression. The world is not a collection of individual facts existing side by side and capable of being known separately. A fact is nothing except in its relations to other facts; and as these relations are multiplied in the progress of knowledge the nature of the so-called fact is indefinitely modified. Moreover, every statement of fact involves certain general notions and theories, so that the “facts” of the separate sciences cannot be stated except in terms of the conceptions or hypotheses which are assumed by the particular science. Thus mathematics assumes space as an existent infinite, without investigating in what sense the existence or the infinity of this “Unding,” as Kant called it, can be asserted. In the same way, physics may be said to assume the notion of material atoms and forces. These and similar assumptions are ultimate presuppositions or working hypotheses for the sciences themselves. But it is the office of philosophy, or theory of knowledge, to submit such conceptions to a critical analysis, with a view to discover how far they can be thought out, or how far, when this is done, they refute themselves, and call for a different form of statement, if they are to be taken as a statement of the ultimate nature of the real. The first statement may frequently turn out to have been merely provisionally or relatively true; it is then superseded by, or rather inevitably merges itself in, a less abstract account. In this the same “facts” appear differently, because no longer separated from other aspects that belong to the full reality of the known world. There is no such thing, we have said, as an individual fact; and the nature of any fact is not fully known unless we know it in all its relations to the system of the universe, or, in Spinoza’s phrase, “sub specie aeternitatis.” In strictness, there is but one res completa or concrete fact, and it is the business of philosophy, as science of the whole, to expound the chief relations that constitute its complex nature.

The last abstraction which it becomes the duty of philosophy to remove is the abstraction from the knowing subject which is made by all the sciences, including, as we shall see, the science of psychology. The sciences, one and all, deal with a world of objects, but the ultimate fact as we know it is the existence of an object for a subject. Subject-object, knowledge, or, more widely, self-consciousness with its implicates—this unity in duality is the ultimate aspect which reality presents. It has generally been considered, therefore, as constituting in a special sense the problem of philosophy. Philosophy may be said to be the explication of what is involved in this relation, or, in modern phraseology, a theory of its possibility. Any would-be theory of the universe which makes its central fact impossible stands self-condemned. On the other hand, a sufficient analysis here may be expected to yield us a statement of the reality of things in its last terms, and thus to shed a light backwards upon the true nature of our subordinate conceptions.

Psychology, Epistemology, and Metaphysics.— This leads to the consideration of our first group of subsidiary sciences — Psychology {q.vf epistemology (theory of knowledge, Erkenntnisstheorie), and metaphysics (ontology; see Meta physic). A special relation has always existed between psychology and systematic philosophy, but the closeness of the connexion has been characteristic of modern and more particularly of English thought. The connexion is not difficult to explain, seeing that in psychology, or the science of mind, we study the fact of intelligence (and moral action), and have, so far, in our hands the fact to which all other facts are relative. From this point of view we may even agree with Sir W. Hamilton when he quotes Jacobi’s dictum—“Nature conceals God; man reveals God.” In other words, as has just been said, the ultimate explanation of things cannot be given by any theory which excludes from its survey the intelligence in which nature, as it were, gathers herself up. But knowledge, or the mind as knowing, willing, <fcc., may be looked at in two different ways. It may be regarded simply as a fact, in which case the evolutions of mind may be traced and reduced to laws in the same way as the phenomena treated by the other sciences. This study gives us the science of empirical psychology, or, as it is now termed, psychology sans phrase. In order to give an adequate account of its subject-matter, psychology may require higher or more complex categories than are employed in the other sciences, just as biology, for example, cannot work with mechanical categories alone, but introduces the conception of development or growth. But the affinities of such a study are manifestly with the sciences as such rather than with philosophy; and it has been already pointed out that the division of labour in this respect is proceeding rapidly. Since it has been taken up by specialists, psychology is being established on a broader basis of induction, and with the advantage, in some departments, of the employment of experimental methods of measurement. But it is not of mind in this aspect that such assertions can be made as those quoted above. Mind, as studied by the psychologist—mind as a mere fact or phenomenon—grounds no inference to anything beyond itself. The distinction between mind viewed as a succession of “states of consciousness” and the further aspect of mind which philosophy considers is very clearly put in a recent article by Professor Croom Robertson, who also makes a happy suggestion of two terms to designate the double point of view.

“We may view knowledge as mere subjective function, but it has its full meaning only as it is taken to represent what we may call objective fact, or is such as is named (in different circumstances) real, valid, true. As mere subjective function, which it is to the psychologist, it is best spoken of by an unambiguous name, and for this there seems none better than Intellection. We may then say that psychology is occupied with the natural function of Intellection, seeking to discover its laws and distinguishing its various modes (perception, representative imagination, conception, &c.) according to the various circumstances in which the laws are found at work. Philosophy, on the other hand, is theory of Knowledge (as that which is known).”—“Psychology and Philosophy,” Mind, 1883, pp. 15, 16.

The confusion of these two points of view has led, and still leads, to serious philosophical misconception. It is hardly an exaggeration to say that, in the English school since Hume, psychology superseded properly philosophical inquiry. The infusion of epistemological matter into the numerous analyses of the human mind rendered the substitution plausible and left men satisfied. And we find even a thinker with a wider horizon like Sir W. Hamilton encouraging the confusion by speaking of “psychology or metaphysics,” while his lectures on metaphysics are mainly taken up with what belongs in the strictest sense to psychology proper, with an occasional excursus (as in the theory of perception) into epistemology. That this confusion is on the way to be obviated for the future is largely due to the Kantian impulse which has been strongly felt of late in English thought, and which has acted in this matter on many who could not, by any laxity of terminology , be numbered as Kantians or Neo-Kantians. The distinction between psychology and theory of knowledge was first clearly made by Kant, who repeatedly insisted that the C ri,tique of Pure Reason was not to be taken as a psychological inquiry. He defined his problem as the quid juins or the question of the validity of knowledge, not its quid facti or the laws of the empirical genesis and evolution of intellection (to use Professor Robertson’s phraseology). Since Kant philosophy has chiefly taken the form of theory of knowledge or of a criticism of experience. Not, indeed, a preliminary criticism of our faculties or conceptions such as Kant himself proposed to institute, in order to determine the limits of their application; such a criticism ab extra of the nature of our experience is essentially a thing impossible. The only criticism which can be applied in such a case is the immanent criticism which the conceptions or categories exercise upon one another. The organized criticism of these conceptions is really nothing more than the full explication of what they mean and of what experience in its full nature or notion is. This constitutes the theory of knowledge, and lays down, in Kantian language, the conditions of the possibility of experience. These conditions are the conditions of knowledge as such, of self-consciousness in general, or, as it may be put, of objective consciousness. The inquiry is, therefore, logical or transcendental in its nature, and does not entangle us in any decision as to the...