FOOTNOTES:

Ontology and Cosmology Concern Being and Process.

§62. It has already been suggested that the test of Thales's conception lay in the possibility of deriving nature from it. A world principle must be fruitful. Now an abstract distinction has prevailed more or less persistently in metaphysics, betweenthe general definition of being, calledontology, and thestudy of the processes wherewith being is divided into things and events. This latter study has to do primarily with the details of experience enumerated and systematized by the natural sciences.To reconcilethese,or the course of nature, with the fundamental definition of being, is the problem ofcosmology. Cosmology is the construing of theprima faciereality in terms of the essential reality. It is the proof and the explanation of ontology. Since the most familiar part of theprima faciereality, the part almost exclusively noticed by the naive mind, is embraced within the field of the physical sciences, the term cosmology has come more definitely to signify thephilosophy of nature. It embraces such an examination of space, time, matter, causality, etc., as seeks to answer the most general questions about them, and provide for them in the world thought of as most profoundly real. Such a study receives its philosophical character from its affiliation with ontology, as the latter would find its application in cosmology.

Mechanical and Teleological Cosmologies.

§63. But in addition to the consideration ofthe various parts of nature, cosmology has commonly dealt with a radical and far-reaching alternative that appeared at the very dawn of metaphysics. Differences may arise within a world constituted of a single substance or a small group of ultimate substances, by changes in the relative position and grouping of the parts. Hence the virtue of the conception of motion. The theory which explains all differences by motions of the parts of a qualitatively simple world, is calledmechanism. Another source of change familiar to naive experience iswill, or the action of living creatures. According to the mechanical theory,changes occur on account of the natural motions of the parts of matter; according to the latter orteleologicalconception,changes are made by a formative agency directed to some end. Among the early Greek philosophers, Leucippus was an exponent of mechanism.

"He says that the worlds arise when many bodies are collected together into the mighty void from the surrounding space and rush together. They come into collision, and those which are of similar shape and like form become entangled, and from their entanglement the heavenly bodies arise."[161:11]

Anaxagoras, on the other hand, was famed for his doctrine of the Nous, or Intelligence, to whose direction he attributed the whole process of the world. The following is translated from extant fragments of his book, "περὶ φύσεως":

"And Nous had power over the whole revolution, so that it began to revolve in the beginning. And it began to revolve first from a small beginning; but the revolution now extends over a larger space, and will extend over a larger still. And all the things that are mingled together and separated off and distinguished are all known by the Nous. And Nous set in order all things that were to be and that were, and all things that are not now and that are, and this revolution in which now revolve the stars and the sun and the moon, and the air and the ether that are separated off."[162:12]

Dualism.

§64. It is clear, furthermore, that the doctrine of Anaxagoras not only names a distinct kind of cause, but also ascribes to it an independence and intrinsic importance that do not belong to motion. Whereas motion is a property of matter, intelligence is an originative power working out purposes of its own choosing. Hence we have here to do with a new ontology. If we construe ultimate being in terms of mind, we have a definite substitute for the physical theories outlined above. Such a theory is scarcely to be attributed to any Greek philosopher of the earlyperiod; it belongs to a more sophisticated stage in the development of thought, after the rise of the problem of epistemology. But Anaxagoras's sharp distinction between the material of the world on the one hand, and the author of its order and evolution on the other, is in itself worthy of notice. It contains the germ of a recurrent philosophicaldualism, which differs from pluralism in that it finds two and only two fundamental divisions of being, the physical, material, or potential on the one hand, and the mental, formal, or ideal on the other.

The New Meaning of Monism and Pluralism.

§65. Finally, the alternative possibilities which these cosmological considerations introduce, bear directly upon the general question of the interdependence of the parts of the world, a question which has already appeared as pertinent in ontology. Monism and pluralism now obtain a new meaning. Where the world process is informed with some singleness of plan, as teleology proposes, the parts are reciprocally necessary, and inseparable from the unity. Where, on the other hand, the processes are random and reciprocally fortuitous, as Leucippus proposes, the world as a whole is an aggregate rather than a unity. In this way uniformity in kind of beingmay prevail in a world the relations of whose parts are due to chance, while diversity in kind of being may prevail in a world knit together by some thorough-going plan of organization. Thus monism and pluralism are conceptions as proper to cosmology as to ontology.

But enough has been said to demonstrate the interdependence of ontology and cosmology, of the theory of being and the theory of differentiation and process. Such problems can be only abstractly sundered, and the distinctive character of any metaphysical system will usually consist in some theory determining their relation. Philosophy returns to these metaphysical problems with its thought enriched and its method complicated, after becoming thoroughly alive to the problems of epistemology, logic, and ethics.

Epistemology Seeks to Understand the Possibility of Knowledge.

§66.Epistemology is the theory of the possibility of knowledge, and issues from criticism and scepticism. If we revert again to the history of Greek philosophy, we find a first period of enterprising speculation giving place to a second period of hesitancy and doubt. This phase of thought occurs simultaneously with the brilliantly humanistic age of Pericles, and it is undoubtedly true that energy iswithdrawn from speculation largely for the sake of expending it in the more lively and engaging pursuits of politics and art. But there are patent reasons within the sphere of philosophy itself for entailment of activity and taking of stock. For three centuries men have taken their philosophical powers for granted, and used them without questioning them. Repeated attacks upon the problem of reality have resulted in no consensus of opinion, but only in a disagreement among the wise men themselves. A great variety of mere theories has been substituted for the old unanimity of religious tradition and practical life. It is natural under these circumstances to infer that in philosophy man has overreached himself. He would more profitably busy himself with affairs that belong to his own sphere, and find a basis for life in his immediate relations with his fellows. The sophists, learned in tradition, and skilled in disputation, but for the most part entirely lacking in originality, are the new prophets. As teachers of rhetoric and morals, they represent the practical and secular spirit of their age; while in their avoidance of speculation, and their critical justification of that course, they express its sceptical philosophy.

Scepticism, Dogmatism, and Agnosticism.

§67. In their self-justification certain of the sophists attached themselves to a definite doctrine maintained by those of their predecessors and contemporaries who were atomists, or followers of that same Leucippus whom we have quoted. This doctrine was the result of an attempt to construe perception in terms of the motion of atoms. Outer objects were said to give off fine particles which, through the mediation of the sense organs, impinged upon the soul-atom. But it was evident even to the early exponents of this theory that according to such an account, each perceiver is relegated to a world peculiar to his own stand-point. His perception informs him concerning his own states as affected by things, rather than concerning the things themselves. Upon this ground the great sophist Protagoras is said to have based his dictum:Πάντων χρημάτων μέτρον ἄνθρωπος,—"Man is the measure of all things." This is the classic statement of the doctrine of relativity. But we have now entered into the province of epistemology, and various alternatives confront us. Reduce thought to perception, define perception as relative to each individual, and you arrive atscepticism, orthe denial of the possibility of valid knowledge. Platoexpounds this consequence in the well-known discussion of Protagoras that occurs in the "Theætetus."

"I am charmed with his doctrine, that what appears is to each one, but I wonder that he did not begin his book on Truth with a declaration that a pig or a dog-faced baboon, or some other yet stranger monster which has sensation, is the measure of all things; then he might have shown a magnificent contempt for our opinion of him by informing us at the outset that while we were reverencing him like a God for his wisdom, he was no better than a tadpole, not to speak of his fellow-men—would not this have produced an overpowering effect? For if truth is only sensation, and no man can discern another's feelings better than he, or has any superior right to determine whether his opinion is true or false, but each, as we have several times repeated, is to himself the sole judge, and everything that he judges is true and right, why, my friend, should Protagoras be preferred to the place of wisdom and instruction, and deserve to be well paid, and we poor ignoramuses have to go to him, if each one is the measure of his own wisdom? . . . The attempt to supervise or refute the notions or opinions of others would be a tedious and enormous piece of folly, if to each man his own are right; and this must be the case if Protagoras's Truth is the real truth, and the philosopher is not merely amusing himself by giving oracles out of the shrine of his book."[167:13]

This is the full swing of the pendulum fromdogmatism, or the uncritical conviction of truth. A modified form of scepticism has been developed in these later days under the influence of naturalscience, and is calledagnosticismorpositivism. It accepts the Protagorean doctrine only in the sense of attributing to human knowledge as a whole an incapacity for exceeding the range of perception. Beyond this realm of natural science, where theories can be sensibly verified, lies the unknowable realm, more real, but forever inaccessible.

The Source and Criterion of Knowledge According to Empiricism and Rationalism. Mysticism.

§68. It is important to note that both scepticism and agnosticism agree in regardingperception as the essential factor in knowledge. So far at any rate as our knowledge is concerned, the certification of being consists in perceivability. Knowledge is coextensive with actual and possible human experience. This account of the source and criterion of knowledge is calledempiricism, in distinction from the counter-theory ofrationalism.

The rationalistic motive was a quickening influence in Greek philosophy long before it became deliberate and conspicuous in Socrates and Plato. Parmenides, founder of the Eleatic School, has left behind him a poem divided into two parts: "The Way of Truth" and "The Way of Opinion."[168:14]In the first of these he expounds hisesoteric philosophy, which is a definition of being established by dialectical reasoning. He finds that being must be single, eternal, and changeless, because otherwise it cannot be thought and defined without contradiction. The method which Parmenides here employs presupposes that knowledge consists in understanding rather than perception. Indeed, he regards the fact that the world of the senses is manifold and mutable as of little consequence to the wise man. The world of sense is the province of vulgar opinion, while that of reason is the absolute truth revealed only to the philosopher. The truth has no concern with appearance, but is answerable only to the test of rationality.That world is real which one is able by thinking to make intelligible.The world is what a world must be in order to be possible at all, and the philosopher can deduce it directly from the very conditions of thought which it must satisfy. He who would know reality may disregard what seems to be, provided he can by reflective analysis discover certain general necessities to which being must conform. This is rationalism in its extreme form.

The rationalism of Socrates was more moderate, as it was more fruitful than that of Parmenides.As is well known, Socrates composed no philosophical books, but sought to inculcate wisdom in his teaching and conversation. His method of inculcating wisdom was to evoke it in his interlocutor by making him considerate of the meaning of his speech. Through his own questions he sought to arouse the questioning spirit, which should weigh the import of words, and be satisfied with nothing short of a definite and consistent judgment. In the Platonic dialogues the Socratic method obtains a place in literature. In the "Theætetus," which is, perhaps, the greatest of all epistemological treatises, Socrates is represented as likening his vocation to that of the midwife.

"Well, my art of midwifery is in most respects like theirs, but differs in that I attend men, and not women, and I look after their souls when they are in labor, and not after their bodies: and the triumph of my art is in thoroughly examining whether the thought which the mind of the young man brings forth is a false idol or a noble and true birth. And, like the midwives, I am barren, and the reproach which is often made against me, that I ask questions of others and have not the wit to answer them myself, is very just; the reason is that the god compels me to be a midwife, but does not allow me to bring forth. And therefore I am not myself at all wise, nor have I anything to show which is the invention or birth of my own soul, but those who converse with me profit. . . . It is quite clear that they neverlearned anything from me; the many fine discoveries to which they cling are of their own making."[171:15]

The principle underlying this method is the insistence that a proposition, to be true of reality, must at least bespeak a mind that is true to itself, internally luminous, and free from contradiction. That which is to me nothing that I can express in form that will convey precise meaning and bear analysis, is so far nothing at all. Being is not, as the empiricist would have it, ready at hand, ours for the looking, but is the fruit of critical reflection. Only reason, overcoming the relativity of perception, and the chaos of popular opinion, can lay hold on the universal truth.

A very interesting tendency to clothe the articulations of thought with the immediacy of perception is exhibited inmysticism, which attributes the highest cognitive power to an experience that transcends thought, an ineffable insight that is the occasional reward of thought and virtuous living. This theory would seem to owe its great vigor to the fact that it promises to unite the universality of the rational object with the vivid presence of the empirical object, though it sacrifices the definite content of both. The mystic, empiricist, andrationalist are in these several ways led to revise their metaphysics upon the basis of their epistemology, or to define reality in terms dictated by the means of knowing it.

The Relation of Knowledge to its Object According to Realism, and the Representative Theory.

§69. But within the general field of epistemology there has arisen another issue of even greater significance in its bearing upon metaphysics. The first issue, as we have seen, has reference to the criterion of knowledge, to the possibility of arriving at certainty about reality, and the choice of means to that end. A second question arises, concerningthe relation between the knowledge and its object or that which is known. This problem does not at first appear as an epistemological difficulty, but is due to the emphasis which the moral and religious interests of men give to the conception of the self. My knowing is a part of me, a function of that soul whose welfare and eternal happiness I am seeking to secure. Indeed, my knowing is, so the wise men have always taught, the greatest of my prerogatives. Wisdom appertains to the philosopher, as folly to the fool. But though my knowledge be a part of me, and in me, the same cannot, lightly at any rate, be said of what I know. It would seem that I mustdistinguish between the knowledge, which is my act or state, an event in my life, and the known, which is object, and belongs to the context of the outer world.The object of knowledgewould then be quiteindependent of the circumstance that I know it. This theory has acquired the name ofrealism,[173:16]and is evidently as close to common sense as any epistemological doctrine can be said to be. If the knowledge consists in some sign or symbol which in my mind stands for the object, but isquite other than the object, realism is given the form known as therepresentative theory. This theory is due to a radical distinction between the inner world of consciousness and the outer world of things, whereby in knowledge the outer object requires a substitute that is qualified to belong to the inner world. Where, on the other hand, no specific and exclusive nature is attributed to the inner world, realism may flourish without the representative theory. In such a case the object would be regarded as itself capable of entering into any number of individual experiences or of remaining outside them all, and without on either account forfeiting its identity. This view was taken for granted by Plato, but is elaborately defended in our own day. During the intervening period epistemology has been largely occupied with difficulties inherent in the representative theory, andfrom that discussion there has emerged the theory ofidealism,[175:17]the great rival theory to that of realism.

The Relation of Knowledge to its Object According to Idealism.

§70. The representative theory contains at least one obvious difficulty. If the thinker be confined to his ideas, and if the reality be at the same time beyond these ideas, how can he ever verify their report? Indeed, what can it mean that an idea should be true of that which belongs to a wholly different category? How under such circumstances can that which is a part of the idea be attributed with any certainty to the object? Once grant that you know only your ideas, and the object reduces to an unknownx, which you retain to account for the outward pointing or reference of the ideas, but which is not missed if neglected. The obvious though radical theory of idealism is almost inevitably the next step. Why assume that there is any object other than the state of mind, since all positive content belongs to that realm? The eighteenth century English philosopher, Bishop Berkeley, was accused by his contemporaries of wilful eccentricity, and even madness, for his boldness in accepting this argument and drawing this conclusion:

"The table I write on I say exists; that is, I see and feel it: and if I were out of my study I should say it existed; meaning thereby that if I was in my study I might perceive it, or that some other spirit actually does perceive it. There was an odor—that is, it was smelt; there was a sound—that is, it was heard; a color or figure, and it was perceived by sight or touch. This is all that I can understand by these and the like expressions. For as to what is said of theabsoluteexistence of unthinking things, without any relation to their being perceived, that is to me perfectly unintelligible. Theiresseispercipi; nor is it possible that they should have any existence out of the minds or thinking thing which perceives them."[176:18]

Phenomenalism, Spiritualism, and Panpsychism.

§71. In this paragraph Berkeley maintains that it is essential to things, or at any rate to their qualities, that theybe perceived. This principle when expressed as an epistemological or metaphysical generalization, is calledphenomenalism. But in another phase of his thought Berkeley emphasizes theperceiver, orspirit. The theory which maintains that the only real substances are these active selves, with their powers and their states, has been called somewhat vaguely by the name ofspiritualism.[176:19]Philosophically it shows a strong tendency todevelop into eitherpanpsychismortranscendentalism. The former is radically empirical. Its classic representative is the German pessimist Schopenhauer, who defined reality in terms of will because that term signified to him most eloquentlythe directly felt nature of the self. This immediate revelation of the true inwardness of being serves as the key to an "intuitive interpretation" of the gradations of nature, and will finally awaken a sense of the presence of the universal Will.

Transcendentalism, or Absolute Idealism.

§72.Transcendentalism, orabsolute idealism, on the other hand, emphasizes therational activity, rather than the bare subjectivity,of the self. The term "transcendental" has become associated with this type of idealism through Kant, whose favorite form of argument, the "transcendental deduction," was an analysis of experience with a view to discovering the categories, or formal principles of thought, implied in its meaning. From the Kantian method arose the conception of a standard orabsolute mindfor the standard experience. This mind is transcendental not in the sense of being alien, but in the sense of exceeding the human mind in the direction of what this means and strives to be. It is the ideal or normal mind, in which the truereality is contained, with all the chaos of finite experience compounded and redeemed. There is no being but the absolute, the one all-inclusive spiritual life, in whom all things are inherent, and whose perfection is the virtual implication of all purposive activities.

"God's life . . . sees the one plan fulfilled through all the manifold lives, the single consciousness winning its purpose by virtue of all the ideas, of all the individual selves, and of all the lives. No finite view is wholly illusory. Every finite intent taken precisely in its wholeness is fulfilled in the Absolute. The least life is not neglected, the most fleeting act is a recognized part of the world's meaning. You are for the divine view all that you know yourself at this instant to be. But you are also infinitely more. The preciousness of your present purposes to yourself is only a hint of that preciousness which in the end links their meaning to the entire realm of Being."[178:20]

The fruitfulness of the philosopher's reflective doubt concerning his own powers is now evident. Problems are raised which are not merely urgent in themselves, but which present wholly new alternatives to the metaphysician. Rationalism and empiricism, realism and idealism, are doctrines which, though springing from the epistemological query concerning the possibility of knowledge, maydetermine an entire philosophical system. They bear upon every question of metaphysics, whether the fundamental conception of being, or the problems of the world's unity, origin, and significance for human life.

[150:1]The post-Kantian movement in Germany—especially in so far as influenced by Hegel. SeeChap. XII.

[151:2]Cf. §203.

[152:3]E. g., the system of Fichte. Cf. §177.

[153:4]SeeChap. XI.

[153:5]Spinoza:On the Improvement of the Understanding. Translation by Elwes, p. 3.

[154:6]Spinoza:Ethics, Part V, Proposition XLII. Translation by Elwes, p. 270.

[155:7]Descartes:Meditations, I. Translation by Veitch, p. 97.

[155:8]Leibniz:New System of the Nature of Substances. Translation by Latta, pp. 299, 300.

[157:9]Burnet:Early Greek Philosophy, p. 42.

[159:10]No little ambiguity attaches to the term "monism" in current usage, because of its appropriation by those who maintain that the universe is unitary and homogeneous inphysical terms(cf. §108). It should properly be used to emphasize the unity of the world in any terms.

[161:11]Burnet:Op. cit., p. 358.

[162:12]Burnet:Op. cit., p. 284.

[167:13]Plato:Theætetus, 161. Translation by Jowett. References to Plato are to the marginal paging.

[168:14]Burnet:Early Greek Philosophy, pp. 184, 187.

[171:15]Plato:Theætetus, 150 B. Translation by Jowett.

[173:16]Much ambiguity attaches to the terms "realism" and "idealism" in current usage. The first had at one time in the history of philosophy a much narrower meaning than that which it now possesses. It was used to apply to those who, after Plato, believed in the independent reality of ideas, universals, or general natures.Realistsin this sense were opposed tonominalistsandconceptualists. Nominalism maintained the exclusive reality of individual substances, and reduced ideas to particular signs having, like thename, a purely symbolical or descriptive value. Conceptualism sought to unite realism and nominalism through the conception of mind, or an individual substance whose meanings may possess universal validity. Though this dispute was of fundamental importance throughout the mediæval period, the issues involved have now been restated. Realism in the old sense will, if held, come within the scope of the broader epistemological realism defined above. Nominalism is covered by empirical tendencies, and conceptualism by modern idealism.The termidealismis sometimes applied to Plato on account of his designation of ideas as the ultimate realities. This would be a natural use of the term, but in our own day it has become inseparably associated with the doctrine which attributes to being a dependence upon the activity of mind. It is of the utmost importance to keep these two meanings clear. In the preferred sense Plato is a realist, and so opposed to idealism.The termidealismis further confused on account of its employment in literature and common speech to denote the control of ideals. Although this is a kindred meaning, the student of philosophy will gain little or no help from it, and will avoid confusion if he distinguishes the term in its technical use and permits it in that capacity to acquire an independent meaning.

The termidealismis sometimes applied to Plato on account of his designation of ideas as the ultimate realities. This would be a natural use of the term, but in our own day it has become inseparably associated with the doctrine which attributes to being a dependence upon the activity of mind. It is of the utmost importance to keep these two meanings clear. In the preferred sense Plato is a realist, and so opposed to idealism.

The termidealismis further confused on account of its employment in literature and common speech to denote the control of ideals. Although this is a kindred meaning, the student of philosophy will gain little or no help from it, and will avoid confusion if he distinguishes the term in its technical use and permits it in that capacity to acquire an independent meaning.

[175:17]Seenote, p. 173.

[176:18]Berkeley:Principles of Human Knowledge, Part I, Fraser's edition, p. 259.

[176:19]To be distinguished from the religious sect which bears the same name.

[178:20]Quoted from Professor Josiah Royce'sThe World and the Individual, First Series, pp. 426-427.

The Normative Sciences.

§73. There are three sets of problems whose general philosophical importance depends upon the place which metaphysics assigns to thehuman critical faculties. Man passes judgment upon that which claims to betrue,beautiful, orgood, thus referring to ideals and standards that define these values. Attempts to make these ideals explicit, and to formulate principles which regulate their attainment, have resulted in the development of the three so-callednormative sciences:logic,æsthetics, andethics. These sciences are said to owe their origin to the Socratic method, and it is indeed certain that their problem is closely related to the general rationalistic attitude.[180:1]In Plato's dialogue, "Protagoras," one may observe the manner of the inception of both ethics and logic. The question at issue between Socrates and the master sophistProtagoras, is concerning the possibility of teaching virtue. Protagoras conducts his side of the discussion with the customary rhetorical flourish, expounding in set speeches the tradition and usage in which such a possibility is accepted. Socrates, on the other hand, conceives the issue quite differently. One can neither affirm nor deny anything of virtue unless one knowswhat is meant by it. Even the possession of such a meaning was scarcely recognized by Protagoras, who was led by Socrates's questions to attribute to the various virtues an external grouping analogous to that of the parts of the face. But Socrates shows that since justice, temperance, courage, and the like, are admittedly similar in that they are all virtues, they must have in common some essence, which is virtue in general. This he seeks to define in the terms,virtue is knowledge. The interest which Socrates here shows in the reduction of the ordinary moral judgments to a system centering in some single fundamental principle, is the ethical interest. But this is at the same time a particular application of the general rationalistic method of definition, and of the general rationalistic postulate that one knows nothing until one can form unitary and determinate conceptions. Therecognition which Socrates thus gives to criteria of knowledge is an expression of the logical interest. In a certain sense, indeed, the whole labor of Socrates was in the cause of the logical interest. For he sought to demonstrate that belief is not necessarily knowledge; that belief may or may not be true. In order that it shall be true, and constitute knowledge, it must be well-grounded, and accompanied by an understanding of its object. Socrates thus set the problem of logic, the discovery, namely, of those characters by virtue of the possession of which belief is knowledge.

The Affiliations of Logic.

§74. Logic deals with the ground of belief, and thus distinguishes itself from the psychological account of the elements of the believing state.[182:2]But it is not possible sharply to sunder psychology and logic. This is due to the fact that the general principles which make belief true, may be regarded quite independently of this fact. They then become themost general truth, belonging to the absolute, archetypal realm, or to the mind of God.[182:3]When the general principles of certainty are so regarded, logic can bedistinguished from metaphysics only by adding to the study of the general principles themselves, the study of the special conditions (mainly psychological) under which they may be realized among men. In the history of human thought the name of logic belongs to the study of thisattainmentof truth, as the terms æsthetics and ethics belong to the studies of the attainment of beauty and goodness.[183:4]It is evident that logic will have a peculiar importance for the rationalist. For the empiricist, proposing to report upon things as they are given, will tend on the whole to maintain that knowledge has no properties save those which are given to it by its special subject-matter. One cannot, in short, define any absolute relationship between the normative sciences and the other branches of philosophy.

Logic Deals with the Most General Conditions of Truth in Belief.

§75.Logic is the formulation, as independently as possible of special subject-matter, of that which conditions truth in belief.Since logic is concerned with truth only in so far as it is predicated of belief, and since belief in so far as true is knowledge, logic can be defined as the formulation of the most general principles of knowledge. The principles soformulated would be those virtually used tojustifybelief or to disprove the imputation of error.

The Parts of Formal Logic. Definition, Self-evidence, Inference, and Observation.

§76. What is calledformal logicis animated with the hope of extracting these formulations directly from an analysis of the procedure of thought. The most general logical principles which have appeared in the historical development of formal logic aredefinition,self-evidence,inference, andobservation. Each of these has been given special study, and each has given rise to special issues.

Definitionhas to do with theformation of concepts, or determinate and unequivocal meanings. The universality of such concepts, and their consequent relation to particular things, was, as we have seen, investigated at a very early date, and gave rise to the great realistic-nominalistic controversy.[184:5]A large part of the logical discussion in the Platonic dialogues is an outgrowth of the earlier "eristic," a form of disputation in favor with the sophists, and consisting in the adroit use of ambiguity.[184:6]It is natural that in its first conscious self-criticism thought should discover the need of definite terms. The perpetual importance ofdefinition has been largely due to the great prestige in modern philosophy of the method of geometry, which was regarded by Descartes and Spinoza as the model for systems of necessary truth.

Self-evidenceis the principle according to whichconviction of truth follows directly from an understanding of meaning. In the practice of his intellectual midwifery, Socrates presupposed that thought is capable of bringing forth its own certainties. And rationalism has at all times regarded truth as ultimately accredited by internal marks recognizable by reason. Such truth arrived at antecedent to acquaintance with instances is calleda priori, as distinguished froma posterioriknowledge, or observation after the fact. There can be no principles of self-evidence, but logicians have always been more or less concerned with the enumeration of alleged self-evident principles, notably those ofcontradictionandidentity. A philosophical interest in the mathematical method has led to a logical study of axioms, but with a view rather to their fruitfulness than their intrinsic truth. Indeed, the interest in self-evident truth has always been subordinate to the interest in systematic truth, and the discovery of first principles most commonly serves to determine the relativepriority of definite concepts, or the correct point of departure for a series of inferences.

The greater part of the famous Aristotelian logic consists in a study ofinference, orthe derivation of new knowledge from old knowledge. Aristotle sought to set down and classify every method of advancing from premises. The most important form of inference which he defined was thesyllogism, a scheme of reasoning to a conclusion by means of two premises having one term in common. From the premises "all men are mortal" and "Socrates is a man," one may conclude that "Socrates is mortal." This is an instance not only of the syllogism in general, but of its most important "mood," the subsumption of a particular case under a general rule. Since the decline of Aristotle's influence in philosophy there has been a notable decrease of interest in the different forms of inference; though its fundamental importance as the very bone and sinew ofreasoningordeductive thinkinghas never been challenged. Its loss of preëminence is in part due to the growth of empiricism, stimulated by the writings of Lord Bacon in the seventeenth century, and fostered by the subsequent development of experimental science.

Observationis the fundamental logical principle of empiricism. For a radical empiricism, knowledge would consist of descriptive generalizations based upon the summation of instances. That branch of logic which deals withthe advance from individual instances to general principles, is calledinductive logic. It has resulted in the announcement of canons of accuracy and freedom from preconception, and in the methodological study of hypothesis, experiment, and verification. Rules for observation directed to the end of discovering causes, constitute the most famous part of the epoch-making logic of J. S. Mills.[187:7]

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