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According to its etymology, the word "philosophy" ( philosophia , from philein , to love, and sophia , wisdom) means "the love of wisdom". This sense appears again in sapientia , the word used in the Middle Ages to designate philosophy.

In the early stages of Greek, as of every other, civilization, the boundary line between philosophy and other departments of human knowledge was not sharply defined, and philosophy was understood to mean "every striving towards knowledge ". This sense of the word survives in Herodotus (I, xxx) and Thucydides (II, xl). In the ninth century of our era, Alcuin, employing it in the same sense, says that philosophy is "naturarum inquisitio, rerum humanarum divinarumque cognitio quantum homini possibile est aestimare" -- investigation of nature, and such knowledge of things human and Divine as is possible for man ( P.L. , CI, 952).

In its proper acceptation, philosophy does not mean the aggregate of the human sciences, but "the general science of things in the universe by their ultimate determinations and reasons"; or again, "the intimate knowledge of the causes and reasons of things", the profound knowledge of the universal order.

Without here enumerating all the historic definitions of philosophy, some of the most significant may be given. Plato calls it "the acquisition of knowledge ", ktêsis epistêmês (Euthydemus, 288 d). Aristotle, mightier than his master at compressing ideas, writes: tên onomazomenên sophian peri ta procirc;ta aitia kai tas archas hupolambanousi pantes -- "All men consider philosophy as concerned with first causes and principles" ( Metaph. , I, i). These notions were perpetuated in the post-Aristotelean schools (Stoicism, Epicureanism, neo-Platonism ), with this difference, that the Stoics and Epicureans accentuated the moral bearing of philosophy ("Philosophia studium summae virtutis", says Seneca in "Epist.", lxxxix, 7), and the neo-Platonists its mystical bearing (see section V below). The Fathers of the Church and the first philosophers of the Middle Ages seem not to have had a very clear idea of philosophy for reasons which we will develop later on ( section IX ), but its conception emerges once more in all its purity among the Arabic philosophers at the end of the twelfth century and the masters of Scholasticism in the thirteenth. St. Thomas, adopting the Aristotelean idea, writes: "Sapientia est scientia quae considerat causas primas et universales causas; sapientia causas primas omnium causarum considerat" -- Wisdom [i.e. philosophy] is the science which considers first and universal causes; wisdom considers the first causes of all causes" (In Metaph. , I, lect. ii).

In general, modern philosophers may be said to have adopted this way of looking at it. Descartes regards philosophy as wisdom: "Philosophiae voce sapientiae studium denotamus" -- "By the term philosophy we denote the pursuit of wisdom" ( Princ. philos. , preface); and he understands by it "cognitio veritatis per primas suas causas" -- " knowledge of truth by its first causes" (ibid.). For Locke, philosophy is the true knowledge of things; for Berkeley, "the study of wisdom and truth " ( Princ. ). The many conceptions of philosophy given by Kant reduce it to that of a science of the general principles of knowledge and of the ultimate objects attainable by knowledge -- "Wissenschaft von den letzten Zwecken der menschlichen Vernunft". For the numerous German philosophers who derive their inspiration from his criticism -- Fichte, Hegel, Schelling, Schleiermacher, Schopenhauer, and the rest -- it is the general teaching of science (Wissenschaftslehre). Many contemporary authors regard it as the synthetic theory of the particular sciences : "Philosophy", says Herbert Spencer, "is completely unified knowledge " ( First Principles , #37). Ostwald has the same idea. For Wundt, the object of philosophy is "the acquisition of such a general conception of the world and of life as will satisfy the exigencies of the reason and the needs of the heart" -- "Gewinnung einer allgemeinen Welt -- und Lebensanschauung, welche die Forderungen unserer Vernunft und die Bedurfnisse unseres Gemüths befriedigen soll" ( Einleit. in d. Philos. , 1901, p. 5). This idea of philosophy as the ultimate science of values (Wert lehre) is emphasized by Windelband, Déring, and others.

The list of conceptions and definitions might be indefinitely prolonged. All of them affirm the eminently synthetic character of philosophy. In the opinion of the present writer, the most exact and comprehensive definition is that of Aristotle. Face to face with nature and with himself, man reflects and endeavours to discover what the world is, and what he is himself. Having made the real the object of studies in detail, each of which constitutes science (see section VIII ), he is led to a study of the whole, to inquire into the principles or reasons of the totality of things, a study which supplies the answers to the last Why 's. The last Why of all rests upon all that is and all that becomes: it does not apply, as in any one particular science (e.g. chemistry), to this or that process of becoming, or to this or that being (e.g. the combination of two bodies), but to all being and all becoming. All being has within it its constituent principles, which account for its substance (constitutive material and formal causes); all becoming, or change, whether superficial or profound, is brought about by an efficient cause other than its subject; and lastly things and events have their bearings from a finality, or final cause. The harmony of principles, or causes, produces the universal order. And thus philosophy is the profound knowledge of the universal order, in the sense of having for its object the simplest and most general principles, by means of which all other objects of thought are, in the last resort, explained.

By these principles, says Aristotle, we know other things, but other things do not suffice to make us know these principles ( dia gar tauta kai ek toutôn t'alla gnôrizetai, all' ou tauta dia tôn hupokeimenôn -- Metaph. , I). The expression universal order should be understood in the widest sense. Man is one part of it: hence the relations of man with the world of sense and with its Author belong to the domain of philosophy. Now man, on the one hand, is the responsible author of these relations, because he is free, but he is obliged by nature itself to reach an aim, which is his moral end. On the other hand, he has the power of reflecting upon the knowledge which he acquires of all things, and this leads him to study the logical structure of science. Thus philosophical knowledge leads to philosophical acquaintance with morality and logic. And hence we have this more comprehensive definition of philosophy: "The profound knowledge of the universal order, of the duties which that order imposes upon man, and of the knowledge which man acquires from reality" -- "La connaissance approfondie de l'ordre universel, des devoirs qui en résultent pour l'homme et de la science que l'homme acquiert de la rémite" (Mercier, "Logique", 1904, p. 23). -- The development of these same ideas under another aspect will be found in section VIII of this article.


Since the universal order falls within the scope of philosophy (which studies only its first principles, not its reasons in detail), philosophy is led to the consideration of all that is: the world, God (or its cause), and man himself (his nature, origin, operations, moral end, and scientific activities).

It would be out of the question to enumerate here all the methods of dividing philosophy that have been given: we confine ourselves to those which have played a part in history and possess the deepest significance.

A. In Greek Philosophy

Two historical divisions dominate Greek philosophy: the Platonic and the Aristotelean.

(1) Plato divides philosophy into dialectic, physics, and ethics. This division is not found in Plato's own writings, and it would be impossible to fit his dialogues into the triple frame, but it corresponds to the spirit of the Platonic philosophy. According to Zeller, Xenocrates (314 B.C.) his disciple, and the leading representative of the Old Academy, was the first to adopt this triadic division, which was destined to go down through the ages ( Grundriss d. Geschichte d. griechischen Philosophie , 144), and Aristotle follows it in dividing his master's philosophy. Dialectic is the science of objective reality, i.e., of the Idea ( idea eidos ), so that by Platonic dialectic we must understand metaphysics. Physics is concerned with the manifestations of the Idea, or with the Real, in the sensible universe, to which Plato attributes no real value independent of that of the Idea. Ethics has for its object human acts. Plato deals with logic, but has no system of logic ; this was a product of Aristotle's genius.

Plato's classification was taken up by his school (the Academy), but it was not long in yielding to the influence of Aristotle's more complete division and according a place to logic. Following the inspirations of the old Academics, the Stoics divided philosophy into physics (the study of the real), logic (the study of the structure of science ) and morals (the study of moral acts). This classification was perpetuated by the neo-Platonists, who transmitted it to the Fathers of the Church , and through them to the Middle Ages.

(2) Aristotle, Plato's illustrious disciple, the most didactic, and at the same time the most synthetic, mind of the Greek world, drew up a remarkable scheme of the divisions of philosophy. The philosophical sciences are divided into theoretic, practical, and poetic, according as their scope is pure speculative knowledge, or conduct ( praxis ), or external production ( poiêsis ). Theoretic philosophy comprises: (a) physics, or the study of corporeal things which are subject to change ( achôrista men all' ouk akinêta ) (b) mathematics, or the study of extension, i.e., of a corporeal property not subject to change and considered, by abstraction, apart from matter ( akinêta men ou chôrista d'isôs, all' hôs en hulê ); (c) metaphysics, called theology, or first philosophy, i.e. the study of being in its unchangeable and (whether naturally or by abstraction ) incorporeal determinations ( chôrista kau akinêt ). Practical philosophy comprises ethics, economics, and politics, the second of these three often merging into the last. Poetic philosophy is concerned in general with the external works conceived by human intelligence. To these may conveniently be added logic, the vestibule of philosophy, which Aristotle studied at length, and of which he may be called the creator.

To metaphysics Aristotle rightly accords the place of honour in the grouping of philosophical studies. He calls it "first philosophy". His classification was taken up by the Peripatetic School and was famous throughout antiquity; it was eclipsed by the Platonic classification during the Alexandrine period, but it reappeared during the Middle Ages.

B. In the Middle Ages

Though the division of philosophy into its branches is not uniform in the first period of the Middle Ages in the West, i.e. down to the end of the twelfth century, the classifications of this period are mostly akin to the Platonic division into logic, ethics, and physics. Aristotle's classification of the theoretic sciences, though made known by Boethius, exerted no influence for the reason that in the early Middle Ages the West knew nothing of Aristotle except his works on logic and some fragments of his speculative philosophy (see section V below). It should be added here that philosophy, reduced at first to dialectic, or logic, and placed as such in the Trivium, was not long in setting itself above the liberal arts.

The Arab philosophers of the twelfth century ( Avicenna, Averroes ) accepted the Aristotelean classification, and when their works -- particularly their translations of Aristotle's great original treatises -- penetrated into the West, the Aristotelean division definitively took its place there. Its coming is heralded by Gundissalinus (see section XII ), one of the Toletan translators of Aristotle, and author of a treatise, "De divisione philosophiae", which was imitated by Michael Scott and Robert Kilwardby . St. Thomas did no more than adopt it and give it a precise scientific form. Later on we shall see that, conformably with the medieval notion of sapientia , to each part of philosophy corresponds the preliminary study of a group of special sciences. The general scheme of the division of philosophy in the thirteenth century, with St. Thomas's commentary on it, is as follows:

There are as many parts of philosophy as there are distinct domains in the order submitted to the philosopher's reflection. Now there is an order which the intelligence does not form but only considers; such is the order realized in nature. Another order, the practical, is formed either by the acts of our intelligence or by the acts of our will, or by the application of those acts to external things in the arts: e.g., the division of practical philosophy into logic, moral philosophy, and æsthetics, or the philosophy of the arts ( "Ad philosophiam naturalem pertinet considerare ordinem rerum quem ratio humana considerat sed non facit; ita quod sub naturali philosophia comprehendamus et metaphysicam. Ordo autem quem ratio considerando facit in proprio actu, pertinet ad rationalem philosophiam, cujus est considerare ordinem partium orationis ad invicem et ordinem principiorum ad invicem et ad conclusiones. Ordo autem actionum voluntariarum pertinet ad considerationem moralis philosophiae. Ordo autem quem ratio considerando facit in rebus exterioribus per rationem humanam pertinet ad artes mechanicas." ) To natural philosophy pertains the consideration of the order of things which human reason considers but does not create -- just as we include metaphysics also under natural philosophy. But the order which reason creates of its own act by consideration pertains to rational philosophy, the office of which is to consider the order of the parts of speech with reference to one another and the order of the principles with reference to one another and to the conclusions. The order of voluntary actions pertains to the consideration of moral philosophy, while the order which the reason creates in external things through the human reason pertains to the mechanical arts. -- In "X Ethic. ad Nic.", I, lect. i.

The philosophy of nature, or speculative philosophy, is divided into metaphysics, mathematics, and physics, according to the three stages traversed by the intelligence in its effort to attain a synthetic comprehension of the universal order, by abstracting from movement (physics), intelligible quantity (mathematics), being ( metaphysics ) ( In lib. Boeth. de Trinitate , Q. v., a. 1). In this classification it is to be noted that, man being one element of the world of sense, psychology ranks as a part of physics.

C. In Modern Philosophy

The Scholastic classification may be said, generally speaking, to have lasted, with some exceptions, until the seventeenth century. Beginning with Descartes, we find a multitude of classifications arising, differing in the principles which inspire them. Kant, for instance, distinguishes metaphysics, moral philosophy, religion, and anthropology. The most widely accepted scheme, that which still governs the division of the branches of philosophy in teaching, is due to Wolff (1679-1755), a disciple of Leibniz, who has been called the educator of Germany in the eighteenth century. This scheme is as follows:

  • Logic.
  • Speculative Philosophy.
  • Practical Philosophy.
  • Wolff broke the ties binding the particular sciences to philosophy, and placed them by themselves; in his view philosophy must remain purely rational. It is easy to see that the members of Wolff's scheme are found in the Aristotelean classification, wherein theodicy is a chapter of metaphysics and psychology a chapter of physics. It may even be said that the Greek classification is better than Wolff's in regard to speculative philosophy, where the ancients were guided by the formal object of the study -- i.e. by the degree of abstraction to which the whole universe is subjected, while the moderns always look at the material object -- i.e., the three categories of being, which it is possible to study, God, the world of sense, and man.

    D. In Contemporary Philosophy

    The impulse received by philosophy during the last half-century gave rise to new philosophical sciences, in the sense that various branches have been detached from the main stems. In psychology this phenomenon has been remarkable: criteriology, or epistemology (the study of the certitude of knowledge ) has developed into a special study. Other branches which have formed themselves into new psychological sciences are: physiological psychology or the study of the physiological concomitant of psychic activities; didactics, or the science of teaching; pedagogy, or the science of education ; collective psychology and the psychology of people (Volkerpsychologie), studying the psychic phenomena observable in human groups as such, and in the different races. An important section of logic (called also noetic, or canonic) is tending to sever itself from the main body, viz., methodology, which studies the special logical formation of various sciences. On moral philosophy, in the wide sense, have been grafted the philosophy of law, the philosophy of society, or social philosophy (which is much the same as sociology ), and the philosophies of religion and of history.


    From what has been said above it is evident that philosophy is beset by a great number of questions. It would not be possible here to enumerate all those questions, much less to detail the divers solutions which have been given to them. The solution of a philosophic question is called a philosophic doctrine or theory. A philosophic system (from sunistêmi , put together) is a complete and organized group of solutions. It is not an incoherent assemblage or an encyclopedic amalgamation of such solutions; it is dominated by an organic unity. Only those philosophic systems which are constructed conformably with the exigencies of organic unity are really powerful: such are the systems of the Upanishads, of Aristotle, of neo-Platonism, of Scholasticism, of Leibniz, Kant and Hume. So that one or several theories do not constitute a system; but some theories, i.e. answers to a philosophic question, are important enough to determine the solution of other important problems of a system. The scope of this section is to indicate some of these theories.

    A. Monism, or Pantheism, and Pluralism, Individualism, or Theism

    Are there many beings distinct in their reality, with one Supreme Being, God at the summit of the hierarchy; or is there but one reality ( monas , hence monism ), one All-God ( pan-theos ) of whom each individual is but a member or fragment (Substantialistic Pantheism ), or else a force, or energy (Dynamic Pantheism )? Here we have an important question of metaphysics the solution of which reacts upon all other domains of philosophy. The system of Aristotle, of the Scholastics, and of Leibniz are Pluralistic and Theistic; the Indian, neo-Platonic, and Hegelian are Monistic. Monism is a fascinating explanation of the real, but it only postpones the difficulties which it imagines itself to be solving (e.g. the difficulty of the interaction of things), to say nothing of the objection, from the human point of view, that it runs counter to our most deep-rooted sentiments.

    B. Objectivism and Subjectivism

    Does being, whether one or many, possess its own life, independent of our mind, so that to be known by us is only accident to being, as in the objective system of metaphysics (e.g. Aristotle, the Scholastics, Spinoza )? Or is being no other reality than the mental and subjective presence which it acquires in our representation of it as in the Subjective system (e.g. Hume)? It is in this sense that the "Revue de métaphysique et de morale" (see bibliography) uses the term metaphysics in its title. Subjectivism cannot explain the passivity of our mental representations, which we do not draw out of ourselves, and which therefore oblige us to infer the reality of a non-ego.

    C. Substantialism and Phenomenism

    Is all reality a flux of phenomena (Heraclitus, Berkeley, Hume, Taine), or does the manifestation appear upon a basis, or substance, which manifests itself, and does the phenomenon demand a noumenon (the Scholastics )? Without an underlying substance, which we only know through the medium of the phenomenon, certain realities, as walking, talking, are inexplicable, and such facts as memory become absurd.

    D. Mechanism and Dynamism (Pure and Modified)

    Natural bodies are considered by some to be aggregations of homogeneous particles of matter (atoms) receiving a movement which is extrinsic to them, so that these bodies differ only in the number and arrangement of their atoms (the Atomism, or Mechanism, of Democritus, Descartes, and Hobbes). Others reduce them to specific, unextended, immaterial forces, of which extension is only the superficial manifestation (Leibniz). Between the two is Modified Dynamism ( Aristotle ), which distinguishes in bodies an immanent specific principle (form) and an indeterminate element (matter) which is the source of limitation and extension. This theory accounts for the specific characters of the entities in question as well as for the reality of their extension in space.

    E. Materialism, Agnosticism, and Spiritualism

    That everything real is material, that whatever might be immaterial would be unreal, such is the cardinal doctrine of Materialism (the Stoics, Hobbes, De Lamettrie). Contemporary Materialism is less outspoken: it is inspired by a Positivist ideology (see section VI ), and asserts that, if anything supra-material exists, it is unknowable ( Agnosticism, from a and gnôsis , knowledge ; Spencer, Huxley). Spiritualism teaches that incorporeal, or immaterial, beings exist or that they are possible (Plato, Aristotle, St. Augustine, the Scholastics, Descartes, Leibniz ). Some have even asserted that only spirits exist: Berkeley, Fichte, and Hegel are exaggerated Spiritualists. The truth is that there are bodies and spirits ; among the latter we are acquainted (though less well than with bodies) with the nature of our soul, which is revealed by the nature of our immaterial acts, and with the nature of God, the infinite intelligence, whose existence is demonstrated by the very existence of finite things. Side by side with these solutions relating to the problems of the real, there is another group of solutions, not less influential in the orientation of a system, and relating to psychical problems or those of the human ego.

    F. Sensualism and Rationalism, or Spiritualism

    These are the opposite poles of the ideogenetic question, the question of the origin of our knowledge. For Sensualism the only source of human knowledge is sensation: everything reduces to transformed sensations. This theory, long ago put forward in Greek philosophy (Stoicism, Epicureanism ), was developed to the full by the English Sensualists (Locke, Berkeley, Hume) and the English Associationists (Brown, Hartley, Priestley); its modern form is Positivism (John Stuart Mill, Huxley, Spencer, Comte, Taine, Littré etc.). Were this theory true, it would follow that we can know only what falls under our senses, and therefore cannot pronounce upon the existence or non-existence, the reality or unreality, of the super-sensible. Positivism is more logical than Materialism. In the New World, the term Agnosticism has been very happily employed to indicate this attitude of reserve towards the super-sensible. Rationalism (from ratio , reason ), or Spiritualism, establishes the existence in us of concepts higher than sensations, i.e. of abstract and general concepts (Plato, Aristotle, St. Augustine, the Scholastics, Descartes, Leibniz, Kant, Cousin etc.). Ideologic Spiritualism has won the adherence of humanity's greatest thinkers. Upon the spirituality, or immateriality, of our higher mental operations is based the proof of the spirituality of the principle from which they proceed and, hence, of the immortality of the soul.

    G. Scepticism, Dogmatism, and Criticism

    So many answers have been given to the question whether man can attain truth, and what is the foundation of certitude, that we will not attempt to enumerate them all. Scepticism declares reason incapable of arriving at the truth, and holds certitude to be a purely subjective affair (Sextus Empiricus, Ænesidemus). Dogmatism asserts that man can attain to truth, and that, in measure to be further determined, our cognitions are certain. The motive of certitude is, for the Traditionalists, a Divine revelation, for the Scotch School (Reid) it is an inclination of nature to affirm the principles of common sense ; it is an irrational, but social, necessity of admitting certain principles for practical dogmatism (Balfour in his "Foundations of Belief" speaks of "non-rational impulse", while Mallock holds that "certitude is found to be the child, not of reason but of custom " and Brunetière writes about "the bankruptcy of science and the need of belief "); it is an affective sentiment, a necessity of wishing that certain things may be verities ( Voluntarism ; Kant's Moral Dogmatism), or the fact of living certain verities (contemporary Pragmatism and Humanism, William James, Schiller). But for others -- and this is the theory which we accept -- the motive of certitude is the very evidence of the connection which appears between the predicate and the subject of a proposition, an evidence which the mind perceives, but which it does not create (Moderate Dogmatism). Lastly for Criticism, which is the Kantian solution of the problem of knowledge, evidence is created by the mind by means of the structural functions with which every human intellect is furnished (the categories of the understanding). In conformity with these functions we connect the impressions of the senses and construct the world. Knowledge, therefore, is valid only for the world as represented to the mind. Kantian Criticism ends in excessive Idealism, which is also called Subjectivism or Phenomenalism, and according to which the mind draws all its representations out of itself, both the sensory impressions and the categories which connect them: the world becomes a mental poem, the object is created by the subject as representation (Fichte, Schelling, Hegel ).

    H. Nominalism, Realism, and Conceptualism

    Nominalism, Realism, and Conceptualism are various answers to the question of the real objectivity of our predications, or of the relation of fidelity existing between our general representations and the external world.

    I. Determinism and Indeterminism

    Has every phenomenon or fact its adequate cause in an antecedent phenomenon or fact (Cosmic Determinism )? And, in respect to acts of the will, are they likewise determined in all their constituent elements (Moral Determinism, Stoicism, Spinoza )? If so, then liberty disappears, and with it human responsibility, merit and demerit. Or, on the contrary, is there a category of volitions which are not necessitated, and which depend upon the discretionary power of the will to act or not to act and in acting to follow freely chosen direction? Does liberty exist? Most Spiritualists of all schools have adopted a libertarian philosophy, holding that liberty alone gives the moral life an acceptable meaning; by various arguments they have confirmed the testimony of conscience and the data of common consent. In physical nature causation and determinism rule; in the moral life, liberty. Others, by no means numerous, have even pretended to discover cases of indeterminism in physical nature (the so-called Contingentist theories, e.g. Boutroux).

    J. Utilitarianism and the Morality of Obligation

    What constitutes the foundation of morality in our actions? Pleasure or utility say some, personal or egoistic pleasure ( Egoism -- Hobbes, Bentham, and "the arithmetic of pleasure"); or again, in the pleasure and utility of all ( Altruism -- John Stuart Mill). Others hold that morality consists in the performance of duty for duty's sake, the observance of law because it is law, independently of personal profit (the Formalism of the Stoics and of Kant ). According to another doctrine, which in our opinion is more correct, utility, or personal advantage, is not incompatible with duty, but the source of the obligation to act is in the last analysis, as the very exigencies of our nature tell us, the ordinance of God.


    Method ( meth' hodos ) means a path taken to reach some objective point. By philosophical method is understood the path leading to philosophy, which, again, may mean either the process employed in the construction of a philosophy (constructive method, method of invention), or the way of teaching philosophy (method of teaching, didactic method). We will deal here with the former of these two senses; the latter will be treated in section XI. Three methods can be, and have been, applied to the construction of philosophy.

    A. Experimental (Empiric, or Analytic) Method

    The method of all Empiric philosophers is to observe facts, accumulate them, and coordinate them. Pushed to its ultimate consequences, the empirical method refuses to rise beyond observed and observable fact; it abstains from investigating anything that is absolute. It is found among the Materialists, ancient and modern, and is most unreservedly applied in contemporary Positivism. Comte opposes the "positive mode of thinking", based solely upon observation, to the theological and metaphysical modes. For Mill, Huxley, Bain, Spencer, there is not one philosophical proposition but is the product, pure and simple, of experience: what we take for a general idea is an aggregate of sensations; a judgment is the union of two sensations; a syllogism, the passage from particular to particular (Mill, "A System of Logic, Rational and Inductive", ed. Lubbock, 1892; Bain, "Logic", New York, 1874). Mathematical propositions, fundamental axioms such as a = a, the principle of contradiction, the principle of causality are only "generalizations from facts of experience" (Mill, op. cit., vii, #5). According to this author, what we believe to be superior to experience in the enunciation of scientific laws is derived from our subjective incapacity to conceive its contradictory; according to Spencer, this inconceivability of the negation is developed by heredity.

    Applied in an exaggerated and exclusive fashion, the experimental method mutilates facts, since it is powerless to ascend to the causes and the laws which govern facts. It suppresses the character of objective necessity which is inherent in scientific judgments, and reduces them to collective formulae of facts observed in the past. It forbids our asserting, e.g., that the men who will be born after us will be subject to death, seeing that all certitude rests on experience, and that by mere observation we cannot reach the unchangeable nature of things. The empirical method, left to its own resources, checks the upward movement of the mind towards the causes or object of the phenomena which confront it.

    B. Deductive, or Synthetic a Priori, Method

    At the opposite pole to the preceding, the deductive method starts from very general principles, from higher causes, to descend ( Latin deducere , to lead down) to more and more complex relations and to facts. The dream of the Deductionist is to take as the point of departure an intuition of the Absolute, of the Supreme Reality -- for the Theists, God ; for the Monists, the Universal Being -- and to draw from this intuition the synthetic knowledge of all that depends upon it in the universe, in conformity with the metaphysical scale of the real.

    Plato is the father of deductive philosophy: he starts from the world of Ideas, and from the Idea of the Sovereign Good, and he would know the reality of the world of sense only in the Ideas of which it is the reflection. St. Augustine, too, finds his satisfaction in studying the universe, and the least of the beings which compose it, only in a synthetic contemplation of God, the exemplary, creative, and final cause of all things. So, too, the Middle Ages attached great importance to the deductive method. "I propose", writes Boethius, "to build science by means of concepts and maxims, as is done in mathematics." Anselm of Canterbury draws from the idea of God, not only the proof of the real existence of an infinite being, but also a group of theorems on His attributes and His relations with the world. Two centuries before Anselm, Scotus Eriugena, the father of anti-Scholasticism, is the completest type of the Deductionist: his metaphysics is one long description of the Divine Odyssey, inspired by the neo-Platonic, monistic conception of the descent of the One in its successive generations. And, on the very threshold of the thirteenth century, Alain de Lille would apply to philosophy a mathematical methodology. In the thirteenth century Raymond Lullybelieved that he had found the secret of "the Great Art" ( ars magna ), a sort of syllogism-machine, built of general tabulations of ideas, the combination of which would give the solution of any question whatsoever. Descartes, Spinoza, and Leibniz are Deductionists: they would construct philosophy after the manner of geometry ( more geometrico ), linking the most special and complicated theorems to some very simple axioms. The same tendency appears among the Ontologists and the post-Kantian Pantheists in Germany (Fichte, Schelling, Hegel ), who base their philosophy upon an intuition of the Absolute Being.

    The deductive philosophers generally profess to disdain the sciences of observation. Their great fault is the compromising of fact, bending it to a preconceived explanation or theory assumed a priori , whereas the observation of the fact ought to precede the assignment of its cause or of its adequate reason. This defect in the deductive method appears glaringly in a youthful work of Leibniz's, "Specimen demonstrationum politicarum pro rege Polonorum eligendo", published anonymously in 1669, where he demonstrates by geometrical methods ( more geometrico ), in sixty propositions, that the Count Palatine of Neuburg ought to be elected to the Polish Throne.

    C. Analytico-Synthetic Method

    This combination of analysis and synthesis, of observation and deduction, is the only method appropriate to philosophy. Indeed, since it undertakes to furnish a general explanation of the universal order (see section I ), philosophy ought to begin with complex effects, facts known by observation, before attempting to include them in one comprehensive explanation of the universe. This is manifest in psychology, where we begin with a careful examination of activities, notably of the phenomena of sense, of intelligence, and of appetite ; in cosmology, where we observe the series of changes, superficial and profound, of bodies; in moral philosophy, which sets out from the observation of moral facts; in theodicy, where we interrogate religious beliefs and feelings; even in metaphysics, the starting-point of which is really existing being.

    But observation and analysis once completed, the work of synthesis begins. We must pass onward to a synthetic psychology that shall enable us to comprehend the destinies of man's vital principle; to a cosmology that shall explain the constitution of bodies, their changes, and the stability of the laws which govern them; to a synthetic moral philosophy establishing the end of man and the ultimate ground of duty ; to a theodicy and deductive metaphysics that shall examine the attributes of God and the fundamental conceptions of all being.

    As a whole and in each of its divisions, philosophy applies the analytic-synthetic method. Its ideal would be to give an account of the universe and of man by a synthetic knowledge of God, upon whom all reality depends. This panoramic view -- the eagle's view of things -- has allured all the great geniuses. St. Thomas expresses himself admirably on this synthetic knowledge of the universe and its first cause. The analytico-synthetic process is the method, not only of philosophy, but of every science, for it is the natural law of thought, the proper function of which is unified and orderly knowledge. "Sapientis est ordinare." Aristotle, St. Thomas, Pascal, Newton, Pasteur, thus understood the method of the sciences. Men like Helmholtz and Wundt adopted synthetic views after doing analytical work. Even the Positivists are metaphysicians, though they do not know it or wish it. Does not Herbert Spencer call his philosophy synthetic? and does he not, by reasoning, pass beyond that domain of the "observable" within which he professes to confine himself?


    Among the many peoples who have covered the globe philosophic culture appears in two groups: the Semitic and the Indo-European, to which may be added the Egyptians and the Chinese. In the Semitic group ( Arabs, Babylonians, Assyrians, Aramaeans, Chaldeans) the Arabs are the most important; nevertheless, their part becomes insignificant when compared with the intellectual life of the Indo-Europeans. Among the latter, philosophic life appears successively in various ethnic divisions, and the succession forms the great periods into which the history of philosophy is divided; first, among the people of India (since 1500 B.C.); then among the Greeks and the Romans (sixth century B.C. to sixth century of our era); again, much later, among the peoples of Central and Northern Europe.

    A. Indian Philosophy

    The philosophy of India is recorded principally in the sacred books of the Veda, for it has always been closely united with religion. Its numerous poetic and religious productions carry within themselves a chronology which enables us to assign them to three periods.

    (1) The Period of the Hymns of the Rig Veda (1500-1000 B.C.)

    This is the most ancient monument of Indo-Germanic civilization; in it may be seen the progressive appearance of the fundamental theory that a single Being exists under a thousand forms in the multiplied phenomena of the universe (Monism).

    (2) The Period of the Brahmans (l000-500 B.C.)

    This is the age of Brahminical civilization. The theory of the one Being remains, but little by little the concrete and anthropomorphic ideas of the one Being are replaced by the doctrine that the basis of all things is in oneself ( âtman ). Psychological Monism appears in its entirety in the Upanishads: the absolute and adequate identity of the Ego -- which is the constitutive basis of our individuality ( âtman ) -- and of all things, with Brahman, the eternal being exalted above time, space, number, and change, the generating principle of all things in which all things are finally reabsorbed -- such the fundamental theme to be found in the Upanishad under a thousand variations of form. To arrive at the âtman, we must not stop at empirical reality which is multiple and cognizable; we must pierce this husk, penetrate to the unknowable and ineffable superessence, and identify ourselves with it in an unconscious unity.

    (3) The Post-Vedic or Sanskrit, Period (since 500 B.C.)

    From the germs of theories contained in the Upanishad a series of systems spring up, orthodox or heterodox. Of the orthodox systems, Vedanta is the most interesting; in it we find the principles of the Upanishads developed in an integral philosophy which comprise metaphysics, cosmology, psychology, and ethics (transmigration, metempsychosis ). Among the systems not in harmony with the Vedic dogmas, the most celebrated is Buddhism , a kind of Pessimism which teaches liberation from pain in a state of unconscious repose, or an extinction of personality (Nirvâna). Buddhism spread in China, where it lives side by side with the doctrines of Lao Tse and that of Confucius. It is evident that even the systems which are not in harmony with the Veda are permeated with religious ideas.

    B. Greek philosophy

    This philosophy, which occupied six centuries before, and six after, Christ, may be divided into four periods, corresponding with the succession of the principal lines of research (1) From Thales of Miletus to Socrates (seventh to fifth centuries B.C. — preoccupied with cosmology) (2) Socrates, Plato, and Aristotle (fifth to fourth centuries B.C. — psychology); (3) From the death of Aristotle to the rise of neo-Platonism (end of the fourth century B.C. to third century after Christ — moral philosophy); (4) neo-Platonic School (from the third century after Christ, or, including the systems of the forerunners of neo-Platonism, from the first century after Christ, to the end of Greek philosophy in the seventh century — mysticism).

    (1) The Pre-Socratic Period

    The pre-Socratic philosophers either seek for the stable basis of things — which is water, for Thales of Miletus; air, for Anaximenes of Miletus; air endowed with intelligence, for Diogenes of Apollonia; number, for Pythagoras (sixth century B.C.); abstract and immovable being, for the Eleatics — or they study that which changes: while Parmenides and the Eleatics assert that everything is, and nothing changes or becomes. Heraclitus (about 535-475) holds that everything becomes, and nothing is unchangeable. Democritus (fifth century) reduces all beings to groups of atoms in motion, and this movement, according to Anaxagoras, has for its cause an intelligent being.

    (2) The Period of Apogee: Socrates, Plato, Aristotle.

    When the Sophists (Protagoras, Gorgias) had demonstrated the insufficiency of these cosmologies, Socrates (470-399) brought philosophical investigation to bear on man himself, studying man chiefly from the moral point of view. From the presence in us of abstract ideas Plato (427-347) deduced the existence of a world of supersensible realities or ideas, of which the visible world is but a pale reflection. These ideas, which the soul in an earlier life contemplated, are now, because of its union with the body, but faintly perceived. Aristotle (384-322), on the contrary, shows that the real dwells in the objects of sense. The theory of act and potentiality, of form and matter, is a new solution of the relations between the permanent and the changing. His psychology, founded upon the principle of the unity of man and the substantial union of soul and body, is a creation of genius. And as much may be said of his logic.

    (3) The Moral Period

    After Aristotle (end of the fourth Century B.C.) four schools are in evidence: Stoic, Epicurean, Platonic, and Aristotelean. The Stoics (Zeno of Citium, Cleanthes, Chrysippus), like the Epicureans, make speculation subordinate to the quest of happiness, and the two schools, in spite of their divergencies, both consider happiness to be ataraxia or absence of sorrow and preoccupation. The teachings of both on nature (Dynamistic Monism with the Stoics, and Pluralistic Mechanism with the Epicureans) are only a prologue to their moral philosophy. After the latter half of the second century B.C. we perceive reciprocal infiltrations between the various schools. This issues in Eclecticism. Seneca (first century B.C.) and Cicero (106-43 B.C.) are attached to Eclecticism with a Stoic basis; two great commentators of Aristotle, Andronicus of Rhodes (first century B.C.) and Alexander of Aphrodisia about 200), affect a Peripatetic Eclecticism. Parallel with Eclecticism runs a current of Scepticism (Ænesidemus, end of first century B.C., and Sextus Empiricus, second century A.D.).

    (4) The Mystical Period

    In the first century B.C. Alexandria had become the capital of Greek intellectual life. Mystical and theurgic tendencies, born of a longing for the ideal and the beyond, began to appear in a current of Greek philosophy which originated in a restoration of Pythagorism and its alliance with Platonism (Plutarch of Chieronea, first century B.C.; Apuleius of Madaura; Numenius, about 160 and others), and still more in the Graeco-Judaic philosophy of Philo the Jew (30 B.C. to A.D. 50). But the dominance of these tendencies is more apparent in neo-Platonism. The most brilliant thinker of the neo-Platonic series is Plotinus (A.D. 20-70). In his "Enneads" he traces the paths which lead the soul to the One, and establishes, in keeping with his mysticism, an emanationist metaphysical system. Porphyry of Tyre (232-304), a disciple of Plotinus, popularizes his teaching, emphasizes its religious bearing, and makes Aristotle's "Organon" the introduction to neo-Platonic philosophy. Later on, neo-Platonism, emphasizing its religious features, placed itself, with Jamblichus, at the service of the pagan pantheon which growing Christianity was ruining on all sides, or again, as with Themistius at Constantinople (fourth century), Proclus and Simplicius at Athens (fifth century), and Ammonius at Alexandria, it took an Encyclopedic turn. With Ammonius and John Philoponus (sixth century) the neo-Platonic School of Alexandria developed in the direction of Christianity.

    C. Patristic philosophy

    In the closing years of the second century and, still more, in the third century, the philosophy of the Fathers of the Church was developed. It was born in a civilization dominated by Greek ideas, chiefly neo-Platonic, and on this side its mode of thought is still the ancient. Still, if some, like St. Augustine, attach the greatest value to the neo-Platonic teachings, it must not be forgotten that the Monist or Pantheistic and Emanationist ideas, which have been accentuated by the successors of Plotinus, are carefully replaced by the theory of creation and the substantial distinction of beings; in this respect a new spirit animates Patristic philosophy. It was developed, too, as an auxiliary of the dogmatic system which the Fathers were to establish. In the third century the great representatives of the Christian School of Alexandria are Clement of Alexandria and Origen. After them Gregory of Nyssa, Gregory of Nazianzus, St. Ambrose, and, above all, St. Augustine (354-430) appear. St. Augustine gathers up the intellectual treasures of the ancient world, and is one of the principal intermediaries for their transmission to the modern world. In its definitive form Augustinism is a fusion of intellectualism and mysticism, with a study of God as the centre of interest. In the fifth century, pseudo-Dionysius perpetuates many a neo-Platonic doctrine adapted to Christianity, and his writings exercise a powerful influence in the Middle Ages.

    D. Medieval philosophy

    The philosophy of the Middle Ages developed simultaneously in the West, at Byzantium, and in divers Eastern centres; but the Western philosophy is the most important. It built itself up with great effort on the ruins of barbarism: until the twelfth century, nothing was known of Aristotle, except some treatises on logic, or of Plato, except a few dialogues. Gradually, problems arose, and, foremost, in importance, the question of universals in the ninth, tenth, and eleventh centuries (see NOMINALISM). St. Anselm (1033-1109) made a first attempt at systematizing Scholastic philosophy, and developed a theodicy. But as early as the ninth century an anti-Scholastic philosophy had arisen with Eriugena who revived the neo-Platonic Monism.

    In the twelfth century Scholasticism formulated new anti-Realist doctrines with Adelard of Bath, Gauthier de Mortagne, and, above all, Abelard and Gilbert de la Porrée, whilst extreme Realism took shape in the schools of Chartres. John of Salisbury and Alain de Lille, in the twelfth century, are the co-ordinating minds that indicate the maturity of Scholastic thought. The latter of these waged a campaign against the Pantheism of David of Dinant and the Epicureanism of the Albigenses — the two most important forms of anti-Scholastic philosophy. At Byzantium, Greek philosophy held its ground throughout the Middle Ages, and kept apart from the movement of Western ideas. The same is true of the Syrians and Arabs.

    But at the end of the twelfth century the Arabic and Byzantine movement entered into relation with Western thought, and effected, to the profit of the latter, the brilliant philosophical revival of the thirteenth century. This was due, in the first place, to the creation of the University of Paris; next, to the foundation of the Dominican and Franciscan orders; lastly, to the introduction of Arabic and