[Footnote 1: Die Erziehung des Menschengeschlects.]

With the thought that every individual must traverse the same course as that by which the race attains its perfection, Lessing connects the idea of the transmigration of souls. Why may not the individual man have been present in this world more than once? Is this hypothesis so ridiculous because it is the oldest?

If Lessing abandoned the ranks of the deists by his recognition of the fact that the positive religions contain truth in a gradual process of purification, by his free criticism, on the other hand, he broke with the orthodox, whose idolatrous reverence for the Bible was to him an abomination. The letter is not the spirit, the Bible is not religion, nor yet its foundation, but only its records. Contingent historical truths can never serve as a proof of the necessary truths of reason. Christianity is older than the New Testament.

Already, in the case of Lessing, we may doubt, in view of his historical temper and of certain speculative tendencies, whether he is to be included among the Illuminati. In the case of Kant a decided protest must be raised against such a classification. When Hegel numbers him among the philosophers of the Illumination, on account of his lack of rational intuition, and some theologians on account of his religious rationalism, the answer to the former is that Kant did not lack the speculative gift, but only that it was surpassed by his gift of reflection, and, to the latter, that in regard to the positive element in religion he judged very differently from the deists and appreciated the historical element more justly than they—if not to the same extent as Lessing and Herder. We do not need to lay great stress on the fact that Kant had a lively consciousness that he was making a contribution to thought, and that the Illumination contemplated this new doctrine without comprehending it, in order to recognize that the difference between his efforts and achievements and those of the Illumination is far greater than their kinship. For although Kant is upon common ground with it, in so far as he adheres to its motto, "Have courage to use thine own understanding, become a man, cease to trust thyself to the guidance of others, and free thyself in all fields from the yoke of authority," and, although besides such formal injunctions to freedom of thought, he also shares in certain material tendencies and convictions (the turning from the world to man, the attempt at a synthesis of reason and experience, and the belief in a religion of reason); yet in method and results, he stands like a giant among a race of dwarfs, like one instructed, who judges from principles, among men of opinion, who merely stick results together, a methodical systematizer among well-meaning but impotent eclectics. The philosophy of the Illumination is related to that of Kant as argument to science, as halting mediation to principiant resolution, as patchwork to creation out of full resources, yet at the same time as wish to deed and as negative preparation to positive achievement. It was undeniably of great value to the Kantian criticism that the Illumination had created a point of intersection for the various tendencies of thought, and had brought about the approximation and mutual contact of the opposing systems which then existed, while, at the same time, it had crumbled them to pieces, and thus awakened the need for a new, more firmly and more deeply founded system.

%4. The Faith Philosophy.%

The philosophers of feeling or faith stand in the same relation to the German Illumination as Rousseau to the French. Here also the rights of feeling are vindicated against those of the knowing reason. Among the distinguished representatives of this anti-rationalistic tendency Hamann led the way, Herder was the most prolific, and Jacobi the clearest. That the fountain of certitude is to be sought not in discriminating thought, but in intuition, experience, revelation, and tradition; that the highest truths can be felt only and not proved; that all existing things are incomprehensible, because individual—these are convictions which, before Jacobi defended them as based on scientific principles, had been vehemently proclaimed by that singular man, J.G. Hamann (died 1788) of Koenigsberg. From an unprinted review by Hamann, Herder drew the objections which his "Metacritique" raises against Kant's Critique of Reason—that the division of matter and form, of sensibility and understanding, is inadmissible; that Kant misunderstood the significance of language, which is just where sensibility and understanding unite, etc.

In Herder[1] (1744-1803: after 1776 Superintendent-General in Weimar) the philosophy of feeling gained a finer, more perspicuous and harmonious nature, who shared Lessing's interest in history and his tendency to hold fast equally to pantheism and to individualism. God is the all-one, infinite, spiritual (non-personal) primal force, which wholly reveals itself in each thing (God: Dialogues on the System of Spinoza, 1787). To the life, power, wisdom, and goodness of God correspond the life and perfection of the universe and of individual creatures, each of which possesses its own irreplaceable value and bears in itself its future in germ. Everywhere, one and the same life in an ascending series of powers and forms with imperceptible transitions. Always, an inner and an outer together; no power without organ, no spirit without a body. As thought is only a higher stage of sensation, which develops from the lower by means of language—reason, like sense, is not a productive but a receptive faculty of knowing, perceiving ("Vernehmen")—so the free process of history is only the continuation and completion of the nature-process (Ideas for the Philosophy of the History of Mankind, 1784 seq.). Man, the last child of nature and her first freedman, is the nodal point where the physical series of events changes into the ethical; the last member of the organisms of earth is at the same time the first in the spiritual development. The mission of history is the unfolding of all the powers which nature has concentrated in man as the compendium of the world; its law, that everywhere on our earth everything be realized that can be realized there; its end, humanity and the harmonious development of all our capacities. As nature forms a single great organism, and from the stone to man describes a connected development, so humanity is a one great individual which passes through its several ages, from infancy (the Orient), through boyhood (Eygpt and Phoenicia), youth (Greece), and manhood (Rome), to old age (the Christian world). The spirit stands in the closest dependence upon nature, and nature is concerned in history throughout. The finer organization of his brain, the possession of hands, above all, his erect position, make man, man and endow him with reason. Similarly it is natural conditions, climate, the character of the soil, the surrounding animal and vegetable life, etc., that play an essential part in determining the manners, the characters, and the destinies of nations. The connection of nature with history by means of the concept of development and through the idea that the two merely represent different stages of the same fundamental process, made Herder the forerunner of Schelling.

[Footnote 1: On Herder cf. the biography by R. Haym, 2 vols., 1877, 1885; and the work by Witte which has been referred to above (p. 306, note).]

His polemic against Kant in the Metacritique, 1799 (against the Critique of Pure Reason), and the dialogue Calligone, 1800 (against the Critique of Judgment), is less pleasing. These are neither dignified in tone nor essentially of much importance. In the former the distinction between sensibility and reason is censured, and in the latter the separation of the beautiful from the true and the good, but Kant's theory of aesthetics is for the most part grossly misunderstood. The "disinterested" satisfaction Herder makes a cold satisfaction; the harmonious activity of the cognitive powers, a tedious, apish sport; the satisfaction "without a concept," judgment without ground or cause. The positive elements in his own views are more valuable. Pleasure in mere form, without a concept, and without the idea of an end, is impossible. All beauty must mean or express something, must be a symbol of inner life; its ground is perfection or adaptation. Beauty is that symmetrical union of the parts of a being, in virtue of which it feels well itself and gives pleasure to the observer, who sympathetically shares in this well-being. The charm and value of the Calligone lie more in the warmth and clearness with which the expressive beauty of single natural phenomena is described than in the abstract discussion.

Friedrich Heinrich Jacobi (1743-1819) gave the most detailed statement of the position of the philosophy of feeling, and the most careful proof of it. He was born in Duesseldorf, the son of a manufacturer; until 1794 he lived in his native place and at his country residence in Pempelfort; later he resided in Holstein, and, from 1805, in Munich, where, in 1807-13, he was president of the Academy of Sciences. Of his works, collected in five volumes, 1812-25, we are here chiefly concerned with the letters On the Doctrine of Spinoza, 1785; David Hume on Faith, or Idealism and Realism, 1787; and the treatise On Divine Things, 1811, which called out Schelling's merciless response, Memorial of Jacobi. Besides Hume and Spinoza, the sensationalism of Bonnet and the criticism of Kant had made the most lasting impression on Jacobi. His relation to Kant is neither that of an opponent nor of a supporter and popularizer. He declares himself in accord with Kant's critique of the understanding (the understanding is merely a formal function, one which forms and combines concepts only, but does not guarantee reality, one to which the material of thought must be given from elsewhere and for which the suprasensible remains unattainable); in regard to the critique of reason he raises the objection that it; makes the Ideas mere postulates, which possess no guarantee for their reality. The critique of sensibility appears to him still more unsatisfactory, as it does not explain the origin of sensations. Without the concept of the "thing-in-itself" one cannot enter the Kantian philosophy, and with it one cannot remain there. Fichte has drawn the correct conclusion from the Kantian premises; idealism is the unavoidable result of the Critique of Reason and foretold by; it as the Messiah was foretold by John the Baptist. And by the evil fruit we know the evil root: the idealistic theory is philosophical nihilism, for it denies the reality of the external world, as the materialism of Spinoza denies a transcendent God and the freedom of the will. Reality slips away from both these systems—they are the only consistent ones there are—material reality escaping from the former and suprasensible reality from the latter; and this must be so, because reality, of whatever kind it be, cannot be known, but only believed and felt. The actual, the existence of the noumenal as well as of the external world, even the existence of our own body, makes itself known to us through revelation alone; the understanding comprehends relations only; the certainty that a thing exists is attained only through experience and faith. Sense and reason are the organs of faith, and hence the true sources of knowledge; the former apprehends the natural, the latter, the supernatural, while for the understanding is left only the analysis and combination of given intuitions.

Philosophy as a science from concepts must necessarily prove atheistic and fatalistic. Conception and proof mean deduction from conditions. How shall that which has no cause from which to explain it, the unconditioned, God, and freedom, be comprehended and proved? Demonstration rises along the chain of causes to the universe alone, not to a transcendent Creator; mediate knowledge is confined to the sphere of conditioned being and mechanical becoming. The intuitive knowledge of feeling alone leads us beyond this, and along with the wonderful, the inconceivable power of freedom in ourselves, which is above all nature, shows us the primal source of all wonders, the transcendent God above us. The inference from our own spiritual, self-conscious, free personality to that of God is no unauthorized anthropomorphism—in the knowledge of God we may fearlessly deify our human existence, because God, when he created man, gave his divine nature human form. Reason and freedom are the same: the former is theoretical, the latter practical elevation to the suprasensible. Nevertheless virtue is not based upon an inflexible, despotic, abstractly, formal law, but upon an instinct, which, however, does not aim at happiness. Thus Jacobi attempts to mediate between the ethics of the Illumination and the ethics of Kant, by agreeing with the former in regard to the origin of virtue (it arises from a natural impulse), and with the latter in regard to its nature (it consists in disinterestedness). Hence with the Illumination he rejects the imperative form, and with Kant the eudemonistic end. At the same time he endeavors to introduce Herder's idea of individuality into ethics, by demanding that morality assume a special form in each man. Schiller and the romantic school take from Jacobi their ideal of the "beautiful soul," which from natural impulse realizes in its action, and still more in its being, the good in an individual way.



%PART II. FROM KANT TO THE PRESENT TIME.%



CHAPTER IX.

KANT.

The suit between empiricism and rationalism had continued for centuries, but still awaited final decision. Are all our ideas the result of experience, or are they (wholly or in part) an original possession of the mind? Are they received from without (by perception), or produced from within (by self-activity)? Is knowledge a product of sensation or of pure thought? All who had thus far taken part in this discussion had resembled partisans or advocates rather than disinterested judges. They had given less attention to investigation than to the defense of the traditional theses of their schools; they had not endeavored to obtain results, but to establish results already determined; and, along with real arguments, popular appeals had not been despised. Each of the opposing schools had given variations on a definite theme, and whenever timid attempts had been made to bring the two melodies into harmony they had met with no approval. The proceedings thus far had at least made it evident to the unbiased hearer that each of the two parties made extravagant claims, and, in the end, fell into self-contradiction. If the claim of empiricism is true, that all our concepts arise from perception, then not only the science of the suprasensible, which it denies, but also the science of the objects of experience, about which it concerns itself, is impossible. For perception informs us concerning single cases merely, it can never comprehend all cases, it yields no necessary and universal truth; but knowledge which is not apodictically valid for every reasoning being and for all cases is not worthy the name. The very reasons which were intended to prove the possibility of knowledge give a direct inference to its impossibility. The empirical philosophy destroys itself, ending with Hume in skepticism and probabilism. Rationalism is overtaken by a different, and yet an analogous fate—it breaks up into a popular eclecticism. It believes that it has discovered an infallible criterion of truth in the clearness and distinctness of ideas, and a sure example for philosophical method in the method of mathematics. In both points it is wrong. The criterion of truth is insufficient, for Spinoza and Leibnitz built up their opposing theories—the pantheism of the one and the monadology of the other—from equally clear and distinct conceptions; tried by this standard individualism is just as true as pantheism. Mathematics, again, does not owe its unquestioned acceptance and cogent force to the clearness and distinctness of its conceptions, but to the fact that these are capable of construction in intuition. The distinction between mathematics and metaphysics was overlooked, namely, that mathematical thought can transform its conceptions into intuitions, can generate its objects or sensuously present them, which philosophical thought is not in a position to do. The objects of the latter must be given to it, and to the human mind they are given in no other way than through sensuous intuition. Metaphysics seeks to be a science of the real, but it is impossible to conjure being out of thought; reality cannot be proved from concepts, it can only be felt. In making the unperceivable and suprasensible (the real nature of things, the totality of the world, the Deity, and immortality) the special object of philosophy, rationalism looked on the understanding as a faculty of knowledge by which objects are given. In reality objects can never be given through concepts; these only render it possible to think objects given in some other way (by intuition). It is true that concepts of the suprasensible exist, but nothing can be known through them, there is nothing intuitively given to be subsumed under them.

With this failure to perceive the intuitive element in mathematics was joined the mistake of overlooking its synthetic character. The syllogistic method of presentation employed in the Euclidean geometry led to the belief that the more special theorems had been derived from the simpler ones, and these from the axioms, by a process of conceptual analysis; while the fact is that in mathematics all progress is by intuition alone, the syllogism serving merely to formulate and explain truths already attained, but not to supply new ones. Following the example of mathematics thus misunderstood, the mission of philosophy was made to consist in the development of the truths slumbering in pregnant first principles by means of logical analysis. If only there were metaphysical axioms! If we only did not demand, and were not compelled to demand, of true science that it increase our knowledge, and not merely give an analytical explanation of knowledge. When once the clearness and distinctness of conceptions had been taken in so purely formal a sense, it was inevitable that in the end, as productivity became less, the principle should be weakened down to a mere demand for the explanation and elucidation of the metaphysical ideas present in popular consciousness. Thus the rationalistic current lost itself in the shallow waters of the Illumination, which soon gave as ready a welcome to the empirical theories—since these also were able to legitimate themselves by clear and distinct conceptions—as it had given to the results of the rationalistic systems.

It was thus easy to see that each of the contending parties had been guilty of one-sidedness, and that in order to escape this a certain mean must be assumed between the two extremes; but it was a much more difficult matter to discover the due middle ground. Neither of the opposing standpoints is so correct as its defenders believe, and neither so false as its opponents maintain. Where, then, on either side, does the mistaken narrowness begin, and how far does the justification of each extend?

The conflict centers, first, about the question concerning the origin of human knowledge and the sphere of its validity. Rationalism is justified when it asserts that some ideas do not come from the senses. If knowledge is to be possible, some concepts cannot originate in perception, those, namely, by which knowledge is constituted, for if they should, it would lack universality and necessity. The sole organ of universally valid knowledge is reason. Empiricism, on the other hand, is justified when it asserts that the experiential alone is knowable. Whatever is to be knowable must be given as a real in sensuous intuition. The only organ of reality is sensibility. Rationalism judges correctly concerning the origin of the most important classes of ideas; empiricism concerning the sphere of their validity. The two may be thus combined: some concepts (those which produce knowledge) take their origin in reason or are a priori, but they are valid for objects of experience alone. The conflict concerns, secondly, the use of the deductive (syllogistic) or the inductive method. Empiricism, through its founder Bacon, had recommended induction in place of the barren syllogistic method, as the only method which would lead to new discoveries. It demands, above all things, the extension of knowledge. Rationalism, on the contrary, held fast to the deductive method, because the syllogism alone, in its view, furnishes knowledge valid for all rational beings. It demands, first of all, universality and necessity in knowledge. Induction has the advantage of increasing knowledge, but it leads only to empirical and comparative, not to strict universality. The syllogism has the advantage of yielding universal and necessary truth, but it can only explicate and establish knowledge, not increase it. May it not be possible so to do justice to the demands of both that the advantages which they seek shall be combined, and the disadvantages which have been feared, avoided? Are there not cognitions which increase our knowledge (are synthetic) without being empirical, which are universally and necessarily valid (a priori) without being analytic? From these considerations arises the main question of the Critique of Pure Reason: How are synthetic judgments a priori possible?

The philosophy of experience had overestimated sense and underestimated the understanding, when it found the source of all knowledge in the faculty of perception and degraded the faculty of thought to an almost wholly inactive recipient of messages coming to it from without. From the standpoint of empiricism concepts (Ideas) deserve confidence only in so far as they can legitimate themselves by their origin in sensations (impressions). It overlooks the active character of all knowing. Among the rationalists, on the other hand, we find an underestimation of the senses and an overestimation of the understanding. They believe that sense reveals only the deceptive exterior of things, while reason gives their true non-sensuous essence. That which the mind perceives of things is deceptive, but that which it thinks concerning them is true. The former power is the faculty of confused, the latter the faculty of distinct knowledge. Sense is the enemy rather than the servant of true knowledge, which consists in the development and explication of pregnant innate conceptions and principles. These philosophers forget that we can never reach reality by conceptual analysis; and that the senses have a far greater importance for knowledge than merely to give it an impulse; that it is they which supply the understanding with real objects, and so with the content of knowledge. Beside the (formal) activity (of the understanding), cognition implies a passive factor, a reception of impressions. Neither sense alone nor the understanding alone produces knowledge, but both cognitive powers are necessary, the active and the passive, the conceptual and the intuitive. Here the question arises, How do concept and intuition, sensuous and rational knowledge, differ, and what is the basis of their congruence? Notwithstanding their different points of departure and their variant results, the two main tendencies of modern philosophy agree in certain points. If the conflict between the two schools and their one-sidedness suggested the idea of supplementing the conclusions of the one by those of the other, the recognition of the incorrectness of their common convictions furnished the occasion to go beyond them and to establish a new, a higher point of view above them both, as also above the eclecticism which sought to unite the opposing principles. The errors common to both concern, in the first place, the nature of judgment and the difference between sensibility and understanding. Neither side had recognized that the peculiar character of judgment consists in active connection. The rationalists made judgment an active function, it is true, but a mere activity of conscious development, of elucidation and analytical inference, which does not advance knowledge a single step. The empiricists described it as a process of comparison and discrimination, as the mere perception and recognition of the relations and connections already existing between ideas; while in reality judgment does not discover the relations and connections of representations, but itself establishes them. In the former case the synthetic moment is ignored, in the latter the active moment. The imperfect view of judgment was one of the reasons for the appearance of extreme theories concerning the origin of ideas in reason or in perception. Rationalism regards even those concepts which have a content as innate, whereas it is only formal concepts which are so. Empiricism regards all, even the highest formal concepts (the categories), as abstracted from experience, whereas experience furnishes only the content of knowledge, and not the synthesis which is necessary to it. On the one hand too much, and on the other too little, is regarded as the original possession of the understanding. The question "What concepts are innate?" can be decided only by answering the further question, What are the concepts through which the faculty of judgment connects the representations obtained from experience? These connective concepts, these formal instruments of synthesis are a priori. The agreement of the two schools is still greater in regard to the relation of sense and understanding, notwithstanding the apparently sharp contrast between them. The empiricist considers thought transformed, sublimated perception, while the rationalist sees in perception only confused and less distinct thought. For the former concepts are faded images of sensations, for the latter sensations are concepts which have not yet become clear; the difference is scarcely greater than if the one should call ice frozen water, and the other should prefer to call water melted ice. Both arrange intuition and thought in a single series, and derive the one from the other by enhancement or attenuation. Both make the mistake of recognizing only a difference in degree where a difference in kind exists. In such a case only an energetic dualism can afford help. Sense and understanding are not one and the same cognitive power at different stages, but two heterogeneous faculties. Sensation and thought are not different in degree, but in kind. As Descartes began with the metaphysical dualism of extension and thought, so Kant begins with the noetical dualism of intuition and thought.

Much more serious, however, than any of the mistakes yet mentioned was a sin of omission of which the two schools were alike guilty, and the recognition and avoidance of which constituted in Kant's own eyes the distinctive character of his philosophy and its principiant-advance beyond preceding systems. The pre-Kantian thinker had proceeded to the discussion of knowledge without raising the question of the possibility of knowledge. He had approached things in the full confidence that the human mind was capable of cognizing them, and with a naive trust in the power of reason to possess itself of the truth. His trust was naive and ingenuous, because the idea that it could deceive him had never entered his mind. Now no matter whether this belief in man's capacity for knowledge and in the possibility of knowing things is justifiable or not, and no matter how far it may be justifiable, it was in any case untested; so that when the skeptic approached with his objections the dogmatist was defenseless. All previous philosophy, so far as it had not been skeptical, had been, according to Kant's expression, dogmatic; that is, it had held as an article of faith, and without precedent inquiry, that we possess the power of cognizing objects. It had not asked how this is possible; it had not even asked what knowledge is, what may and must be demanded of it, and by what means our reason is in a position to satisfy such demands. It had left human intelligence and its extent uninvestigated. The skeptic, on the other hand, had been no more thorough. He had doubted and denied man's capacity for knowledge just as uncritically as the dogmatist had believed and presupposed it. He had directed his ingenuity against the theories of dogmatic philosophy, instead of toward the fundamental question of the possibility of knowledge. Human intelligence, which the dogmatist had approached with unreasoned trust and the skeptic with just as unreasoned distrust, is subjected, according to the plan of the critical philosopher, to a searching examination. For this reason Kant termed his standpoint "criticism," and his undertaking a "Critique of Reason." Instead of asserting and denying, he investigates how knowledge arises, of what factors it is composed, and how far it extends. He inquires into the origin and extent of knowledge, into its sources and its limits, into the grounds of its existence and of its legitimacy. The Critique of Reason finds itself confronted by two problems, the second of which cannot be solved until after the solution of the first. The investigation of the sources of knowledge must precede the inquiry into the extent of knowledge. Only after the conditions of knowledge have been established can it be ascertained what objects are attainable by it. Its sphere cannot be determined except from its origin.

Whether the critical philosopher stands nearer to the skeptic or to the dogmatist is rather an idle question. He is specifically distinct from both, in that he summons and guides the reason to self-contemplation, to a methodical examination of its capacity for knowledge. Where the one had blindly trusted and the other suspected and denied, he investigates; they overlook, he raises the question of the possibility of knowledge. The critical problem does not mean, Does a faculty of knowledge exist? but, Of what powers is it composed? are all objects knowable which have been so regarded? Kant does not ask whether, but how and by what means, knowledge is possible. Everyone who gives himself to scientific reflection must postulate that knowledge is possible, and the demand of the noetical theorists of the day for a philosophy absolutely without assumptions is quite incapable of fulfillment. Nay, in order to be able to begin his inquiry at all, it was necessary for Kant to assume still more special postulates; for that a cognition of cognition is possible, that there is a critical, self-investigating reason could, at first, be only a matter of belief. This would not have excluded a supplementary detailed statement concerning the how of this self-knowledge, concerning the organ of the critical philosophy. But Kant never gave one, and the omission subsequently led to a sharp debate concerning the character and method of the Critique of Reason. On this point, if we may so express it, Kant remained a dogmatist.

Kant felt himself to be the finisher of skepticism; but this was chiefly because he had received the strongest impulse to the development of his critique of knowledge from Hume's inquiries concerning causation. Brought up in the dogmatic rationalism of the Wolffian school, to which he remained true for a considerable period as a teacher and writer (till about 1760), although at the same time he was inquiring with an independent spirit, Kant was gradually won over through the influence of the English philosophy to the side of empirical skepticism. Then—as the result, no doubt, of reading the Nouveaux Essais of Leibnitz, published in 1765—he returned to rationalistic principles, until finally, after a renewal of empirical influences,[1] he took the position crystallized in the Critique of Pure Reason, 1781, which, however, experienced still other, though less considerable, changes in the sequel, just as in itself it shows the traces of previous transformations.

[Footnote 1: Cf. H. Vaihinger's Kommentar zu Kants Kritik der reinen Vernunft, vol. i., 1881, pp. 48-49. This is a work marked by acuteness, great industry, and an objective point of view which merits respect. The second volume, which treats of the Transcendental Aesthetic, appeared in 1892.]

It would be a most interesting task to trace in the writings which belong to Kant's pre-critical period the growth and development of the fundamental critical positions. Here, however, we can only mention in passing the subjects of his reflection and some of the most striking anticipations and beginnings of his epoch-making position. Even his maiden work, Thoughts on the True Estimation of Vis Viva, 1747, betokens the mediating nature of its author. In this it is argued that when men of profound and penetrating minds maintain exactly opposite opinions, attention must be chiefly directed to some intermediate principle to a certain degree compatible with the correctness of both parties. The question under discussion was whether the measure of vis viva is equal, as the Cartesians thought, to the product of the mass into the velocity, or, according to the Leibnitzians, to the product of the mass into the square of the velocity. Kant's unsatisfactory solution of the problem—the law of Descartes holds for dead, and that of Leibnitz for living forces—drew upon him the derision of Lessing, who said that he had endeavored to estimate living forces without having tested his own. A similar tendency toward compromise—this time it is a synthesis of Leibnitz and Newton—is seen in his Habilitationsschrift, Principiorum Primorum Cognitionis Metaphysicae Nova Dilucidatio, 1755, and in the dissertation Monadologia Physica, 1756. The former distinguishes between ratio essendi and ratio cognoscendi, rejects the ontological argument, and defends determinism against Crusius on Leibnitzian grounds. In the Physical Monadology Kant gives his adherence to dynamism (matter the product of attraction and repulsion), and makes the monads or elements of body fill space without prejudice to their simplicity. A series of treatises is devoted to subjects in natural science: The Effect of the Tides in retarding the Earth's Rotation; The Obsolescence of the Earth; Fire (Inaugural Dissertation), Earthquakes, and the Theory of the Winds. The most important of these, the General Natural History and Theory of the Heavens, 1755, which for a long time remained unnoticed, and which was dedicated to Frederick II., developed the hypothesis (carried out forty years later by Laplace in ignorance of Kant's work) of the mechanical origin of the universe and of the motion of the planets. It presupposes merely the two forces of matter, attraction and repulsion, and its primitive chaotic condition, a world-mist with elements of different density. It is noticeable that Kant acknowledges the failure of the mechanical theory at two points: it is brought to a halt at the origin of the organic world and at the origin of matter. The mechanical cosmogony is far from denying creation; on the contrary, the proof that this well-ordered and purposive world necessarily arose from the regular action of material forces under law and without divine intervention, can only serve to support our assumption of a Supreme Intelligence as the author of matter and its laws; the belief is necessary, just because nature, even in its chaotic condition, can act only in an orderly and regular way.

The empirical phase of Kant's development is represented by the writings of the 60's. The False Subtlety of the Four Syllogistic Figures, 1762, asserts that the first figure is the only natural one, and that the others are superfluous and need reduction to the first. In the Only Possible Foundation for a Demonstration of the Existence of God, 1763, which, in the seventh Reflection of the Second Division, recapitulates the cosmogony advanced in the Natural History of the Heavens, the discussions concerning being ("existence" is absolute position, not a predicate which increases the sum of the qualities but is posited in a merely relative way), and the conclusion, prophetical of his later point of view, "It is altogether necessary that we should be convinced of the existence of God, but not so necessary that his existence should be demonstrated" are more noteworthy than the argument itself. This runs: All possibility presupposes something actual wherein and whereby all that is conceivable is given as a determination or a consequence. That actuality the destruction of which would destroy all possibility is absolutely necessary. Therefore there exists an absolutely necessary Being as the ultimate real ground of all possibility; this Being is one, simple, unchangeable, eternal, the ens realissimum and a spirit. The Attempt to introduce the Notion of Negative Quantities into Philosophy, 1763, distinguishes—contrary to Crusius—between logical opposition, contradiction or mere negation (a and not-a, pleasure and the absence of pleasure, power and lack of power), and real opposition, which cannot be explained by logic (+a and -a, pleasure and pain, capital and debts, attraction and repulsion; in real opposition both determinations are positive, but in opposite directions). Parallel with this it distinguishes, also, between logical ground and real ground. The prize essay, Inquiry concerning the Clearness (Evidence) of the Principles of Natural Theology and Ethics, 1764, draws a sharp distinction between mathematical and metaphysical knowledge, and warns philosophy against the hurtful imitation of the geometrical method, in place of which it should rather take as an example the method which Newton introduced into natural science. Quantity constitutes the object of mathematics, qualities, the object of philosophy; the former is easy and simple, the latter difficult and complicated—how much more comprehensible the conception of a trillion is than the philosophical idea of freedom, which the philosophers thus far have been unable to make intelligible. In mathematics the general is considered under symbols in concrete, in philosophy, by means of symbols in abstracto; the former constructs its object in sensuous intuition, while the object of the latter is given to it, and that as a confused concept to be decomposed. Mathematics, therefore, may well begin with definitions, since the conception which is to be explained is first brought into being through the definition, while philosophy must begin by seeking her conceptions. In the former the definition is first in order, and in the latter almost always last; in the one case the method is synthetic, in the other it is analytic. It is the function of mathematics to connect and compare clear and certain concepts of quantity in order to draw conclusions from them; the function of philosophy is to analyze concepts given in a confused state, and to make them detailed and definite. Philosophy has also this disadvantage, that it possesses very many undecomposable concepts and undemonstrable propositions, while mathematics has only a few such. "Philosophical truths are like meteors, whose brightness gives no assurance of their permanence. They vanish, but mathematics remains. Metaphysics is without doubt the most difficult of all human sciences (Einsichten), but a metaphysic has never yet been written"; for one cannot be so kind as to "apply the term philosophy to all that is contained in the books which bear this title." In the closing paragraphs, on the ultimate bases of ethics, the stern features of the categorical imperative are already seen, veiled by the English theory of moral sense, while the attractive Observations on the Feeling of the Beautiful and the Sublime, which appeared in the same year, still naively follow the empirical road.

The empirical phase reaches its skeptical termination in the satire Dreams of a Ghost-seer explained by the Dreams of Metaphysics, 1766, which pours out its ingenious sarcasm impartially on spiritualism and on the assumed knowledge of the suprasensible. Here Kant is already clearly conscious of his new problem, a theory of the limits of human reason, conscious also that the attack on this problem is to be begun by a discussion of the question of space. This second question had been for many years a frequent subject of his reflections;[1] and it was this part of the general critical problem that first received definitive solution. In the Latin dissertation On the Form and Principles of the Sensible and Intelligible World, 1770, which concludes the pre-critical period, and which was written on the occasion of his assumption of his chair as ordinary professor, the critique of sensibility, the new theory of space and time, is set forth in approximately the same form as in the Critique of Pure Reason, while the critique of the understanding and of reason, the theory of the categories and the Ideas and of the sphere of their validity, required for its completion the intellectual labor of several more years. For this essay, De Mundi Sensibilis atque Intelligibilis Forma et Principiis, leaves unchallenged the possibility of a knowledge of things in themselves and of God, thus showing that its author has abandoned the skepticism maintained in the Dreams of a Ghost-seer, and has turned anew to dogmatic rationalism, whose final overthrow required another swing in the direction of skeptical empiricism. In regard to the progress of this latter phase of opinion, the letters to M. Herz are almost the only, though not very valuable, source of information.

[Footnote 1: New Theory of Motion and Rest, 1758; On the First Ground of the Distinction of Positions in Space, 1768; besides several of the works mentioned above.]

The Critique of Pure Reason appeared in 1781, much later than Kant had hoped when he began a work on "The Limits of Sensibility and Reason," and a second, altered edition in 1787.[1] After the Prolegomena to every Future Metaphysic which may present itself as Science, 1783, had given a popular form to the critical doctrine of knowledge, it was followed by the critical philosophy of ethics in the Foundation of the Metaphysics of Ethics, 1785, and the Critique of Practical Reason, 1788; by the critical aesthetics and teleology in the Critique of Judgment, 1790; and by the critical philosophy of religion in Religion within the Limits of Reason Only, 1793[2] (consisting of four essays, of which the first, "Of Radical Evil," had already appeared in the Berliner Monatsschrift in 1792). The Metaphysical Elements of Natural Science, 1786, and the Metaphysics of Ethics, 1797 (in two parts, "Metaphysical Elements of the Theory of Right," and "Metaphysical Elements of the Theory of Virtue "), are devoted to the development of the system. The year 1798 brought two more larger works, the Conflict of the Faculties and the Anthropology. Of the reviews, that on Herder's Ideen maybe mentioned, and among the minor essays, the following: Idea for a Universal History in a Cosmopolitan Sense, Answer to the Question: What is Illumination f both in 1784; What does it mean to Orient oneself in Thought? 1786; On the Use of Teleological Principles in Philosophy, 1788; On a Discovery according to which all Recent Criticism of Pure Reason is to be superseded by a Previous One, 1790; On the Progress of Metaphysics since the Time of Wolff; On Philosophy in General, The End of all Things, 1794; On Everlasting Peace, 1795. Kant's Logic was published by Jaesche in 1800; his Physical Geography and his Observations on Pedagogics by F.T. Rink in 1803; his lectures on the Philosophical Theory of Religion (1817; 2d. ed., 1830) and on Metaphysics (1821; cf. Benno Erdmann in the Philosophische Monatshefte, vol. xix. 1883, p. 129 seq., and vol. xx. 1884, p. 65 seq.) by Poelitz. If we may judge by the specimens given by Reicke in the Altpreussische Monatsschrift, 1882-84, and by Krause himself,[3] the promised publication of a manuscript of Kant's last years, now in possession of the Hamburg pastor, Albrecht Krause, and which discusses the transition from the metaphysical elements of natural science to physics, will hardly meet the expectations which some have cherished concerning it. Benno Erdmann has issued Nachtraege zu Kants Kritik der reinen Vernunft aus Kants Nachlass, 1881, and Reflexionen Kants zur kritischen Philosophie aus handschriftlichen Aufzeichnungen—the first volume first Heft (Reflexionen zur Anthropologie) appearing in 1882, the second volume (Reflexionen zur Kritik der reinen Vernunft, aus Kants Handexemplar von Baumgartens Metaphysica) in 1884. Max Mueller has made an English translation of the Critique of Pure Reason, 2 vols., 1881.[4]

[Footnote 1: There has been much discussion and much has been written concerning the relation of the two editions. In opposition to Schopenhauer and Kuno Fischer it must be maintained that the alterations in the second edition consist in giving greater prominence to realistic elements, which in the first edition remained in the background, though present even there.]

[Footnote 2: This publication was the occasion of a conflict between Kant and the censorship concerning the right of free religious inquiry; cf. Dilthey in the Archiv fuer Geschichte der Philosophie, vol. in. 1890, pp. 418-450.]

[Footnote 3: A. Krause: I. Kant wider K. Fischer, zum ersten Male mit Huelfe des verloren gewesenen Kantischen Hauptwerkes vertheidigt, 1884 (in reply, K. Fischer, Das Streber- und Gruenderthum in der Litteratur, 1884); also, Das nachgelassene Werk I. Kants, mit Belegen populaer-wissenschaftlich dargestellt, 1888.]

[Footnote 4: Besides this (centenary) translation the English reader may be referred to the earlier version of Meiklejohn in Bonn's Library; to the versions of the Prolegomena by Bax (also in Bonn's Library, and including the Metaphysical Elements of Natural Science), and Mahaffy and Bernard, new ed., 1889; to Abbot's Kant's Theory of Ethics, 4th ed., 1889, containing the Foundation of the Metaphysics of Ethics and the Critique of Practical Reason entire, with portions of the Metaphysics of Ethics and Religion within the Limits of Reason Only; to Bernard's translation of the Kritik of Judgment, 1892; and to Watson's Selections from Kant, 2d ed., 1888 (in Sneath's Modern Philosophers, 1892).—TR.]

The best complete edition of the works of Kant is the second edition of Hartenstein, in eight volumes, 1867-68, which is chronologically arranged and excellently gotten up. Simultaneously with the first edition of Hartenstein in ten volumes, in 1838 seq., appeared the edition in twelve volumes by K. Rosenkranz and F.W. Schubert (containing in the last volumes a biography of Kant by Schubert, and a history of the Kantian philosophy by Rosenkranz, 1842). Kehrbach's edition of the principal works in Reclam's Universal-Bibliothek, with the pagination of the original and collective editions (1877 seq.), is more valuable than Von Kirchmann's edition of the complete works in his Philosophische Bibliothek.

Among the works on Kant those of Kuno Fischer (vols. iii.-iv. of the Geschichte der neueren Philosophie, 3d ed., 1882; also Kant's Leben und die Grundlagen seiner Lehre, 1860) take the first place. The writings of Liebmann, Cohen, Stadler, Riehl, Volkelt, and others will be mentioned later, in connection with the neo-Kantian movement; here we may give some of the more important monographs and essays, selected from the enormously developed Kantian literature:

Ad. Boehringer, Kants erkenntnisstheoretischer Idealismus, 1888; K. Dieterich, Die Kantische Philosophie in ihrer inneren Entwickelungsgeschichte, 2 parts, 1885 (first published separately, Kant und Newton, 1877; Kant und Rousseau, 1878); W. Dilthey, Aus den Rostocker Kanthandschriften in the Archiv fuer Geschichte der Philosophie, vols. ii.-iii. 1889-90; M.W. Drobisch, Kants Ding an sich und sein Erfahrungsbegriff, 1885; B. Erdmann, Kants Kritizismus in der I. und II. Auflage der Kritik der reinen Vernunft, 1878; the same, Kants Prolegomena herausgegeben und erlaeutert, 1878, Introduction (in reply Emil Arnoldt, Kants Prolegomena nicht doppelt redigiert, 1879; cf. also H. Vaihinger, Die Erdmann-Arnoldtsche Kontroverse in the Philosophische Monatshefte, vol. xvi. 1880); Franz Erhardt, Kritik der Kantischen Antinomienlehre, 1888; R. Eucken, Ueber Bilder und Gleichnisse bei Kant, Zeitschrift fuer Philosophie, vol. lxxxiii, 1883, reprinted in his Beitraege zur Geschichte der neueren Philosophie, 1886; F. Frederichs, Der phaenomenale Idealismus Berkeleys und Kants, 1871; the same, Kants Prinzip der Ethik, 1879; Ed. von Hartmann, Das Ding an sich und seine Beschaffenheit, 1871, in the 2d ed., 1875, and the 3d, 1885, entitled Kritische Grundlegung des transzendentalen Realismus; C. Hebler, Kantiana, in his Philosophische Aufsaetze, 1869; Alfred Hegler, Die Psychologie in Kants Ethik, 1891; A. Hoelder, Darstellung der Kantischen Erkenntnisstheorie, 1873 J. Jacobson, Die Auffindung des Apriori, 1876; the same, Ueber die Beziehungen zwischen Kategorien und Urtheilsformen, 1877; Wilhelm Koppelmann, Kants Lehre vom analytischen Urtheil, Philosoph. Monatshefte, vol. xxi, 1885; the same, Lotzes Stellung zu Kants Kritizismus, Zeitschrift fuer Philosophie, vol. lxxxviii, 1886; the same, Kants Lehre vom kategorischen Imperativ, 1888; the same, Kant und die Grundlagen der Christlichen Religion, 1890; E. Laas, Kants Analogien der Erfahrung, 1876; the same, Einige Bemerkungen zur Transzendentalphilosophie, Strassburg Abhandlungen, 1884; J. Mainzer, Die kritische Epoche in der Lehre von der Einbildungskraft, 1881; J.B. Meyer, Kants Psychologie, 1870; F. Paulsen, Was Kant uns sein kann, Vierteljahrsschrift fuer wissenschaftliche Philosophie, 1881; B. Puenjer, Die Religionslehre Kants, 1874; R. Quaebicker, Kants und Herbarts metaphysische Grundansichten ueber das Wesen der Seele, 1870; J. Rehmke, Physiologie und Kantianismus, address in Eisenach, 1883; Rud. Reicke, Lose Blaetter aus Kants Nachlass, 1889 (on this H. Vaihinger in the Zeitschrift fuer Philosophie, vol. xcvi. 1889); O. Riedel, Die monadologischen Bestimmungen in Kants Lehre vom Ding an sich, dissertation at Kiel, 1884; O. Schneider, Die psychologische Entwickelung des Apriori, 1883; the same, Transzendentalpsychologie, 1891; F. Staudinger, Noumena, 1884; M. Steckelmacher, Die formale Logik Kants, Breslau Prize Essay, 1879; A. Stern, Die Beziehung Garves zu Kant, nebst ungedruckten Briefen, 1884; C. Stumpf, Psychologie und Erkenntnisstheorie, Abhandlungen der bayerischen Akademie der Wissenschaften, 1891; G. Thiele, Kants intellectuelle Anschauung als Grundbegriff seines Kritizismus, 1876; the same, Die Philosophie Kants nach ihrem systematischen Zusammenhange und ihrer logischhistorischen Entiwickelung, I. (1) Kants vorkritische Naturphilosophie, 1882; (2) Kants vorkritische Erkenntnisstheorie, 1887; Ad. Trendelenburg, Ueber eine Luecke in Kants Beweis von der ausschliessenden Subjectivitaet des Raumes and der Zeit in vol. iii. of his Historische Beitraege zur Philosophie, 1867; Ueberhorst, Kants Lehre von dem Verhaeltnisse der Kategorien zu der Erfahrung, 1878; H. Vaihinger, Eine Blattversetzung in Kants Prolegomena, Philosoph. Monatshefte, vol. xv. 1879; the same, Zu Kants Widerlegung des Idealismus, Strassburg Abhandlungen, 1884; J. Walter, Zum Gedaechtniss Kants, Festrede, 1881; Th. Weber, Zur Kritik der Kantischen Erkenntnisstheorie (from the Zeitschrift fuer Philosophie), 1882; W. Windelband, Ueber die verschiedenen Phasen der Kantischen Lehre vom Ding an sich, Vierteljahrsschrift fuer wissenschaftliche Philosophie, 1877 (cf. the same author's Geschichte der neueren Philosophie, Sec. 58); J. Witte, Beitraege zum Verstaendniss Kants, 1874; the same, Kantischer Kritizismus gegenueber unkritischem Dilettantismus (against A. Stoehr), 1885; Wohlrabe, Kants Lehre vom Gewissen, 1889; E. Zeller, Ueber das Kantische Moralprinzip, 1880; R. Zimmermann, Ueber Kants Widerlegung des Idealismus von Berkeley, 1871; the same, Ueber Kants mathematisches Vorurtheil und dessen Folgen, 1871.

Popular expositions have been given by the following: K. Fortlage (in his Philos. Vortraege, 1869); E. Last, Mehr Licht! Die Haupsaetze Kants und Schopenhauers, 1879; the same, Die realistiche und die idealistische Anschauung entwickelt an Kants Idealitaet von Raum und Zeit, 1884; H. Romundt, Antaeus, neuer Aufbau der Lehre Kants ueber Seele, Freiheit, und Gott, 1882; the same, Grundlegung zur Reform der Philosophie, vereinfachte und erweiterte Darstellung von Kants Kritik der reinen Vernunft, 1885; the same, Die Vollendung des Socrates, Kants Grundlegung zur Reform der Sittenlehre; the same, Ein neuer Paulus, Kants Grundlegung zu einer sicheren Lehre von der Religion, 1886; the same, Die drei Fragen Kants, 1887; A. Krause, Populaere Darstellung von Kants Kritik der reinen Vernunft, 1881; K. Lasswitz, Die Lehre Kants von der Idealitaet des Raumes und der Zeit, 1883; Wilhelm Muenz, Die Grundlagen der Kantischen Erkenntnisstheorie, 2d ed., 1885.

Among foreigners Villers, Cousin, Nolen, Desdouits, Cantoni, E. Caird [A Critical Account of the Philosophy of Kant, 1877; The Critical Philosophy of Immanuel Kant, 2 vols., 1889], Adamson [On the Philosophy of Kant, 1879, and a valuable article in the Encyclopedia Britannica, 9th ed., vol. xiii.], Stirling [Text-book to Kant, 1881], [Watson, Kant and his English Critics, 1881], Morris Kant's Critique of Pure Reason, Griggs's Philosophical Classics, 1882, [Wallace, Kant, Blackwood's Philosophical Classics, 1882; Porter, Kant's Ethics, Griggs's Philosophical Classics, 1886; Green, Lectures, Works, vol. ii., 1886.—Tr.], have among others made contributions to Kantian literature. Of the older works we may mention the dictionaries of E. Schmid, 1788, and Mellin (in six volumes), 1797 seq., the critique of the Kantian philosophy in the first volume of Schopenhauer's chief work, 1819, and the essay of C.H. Weisse, In welchem Sinne hat sich die deutsche Philosophie jetzt wieder an Kant zu orientieren, 1847.

Kant's outward life was less eventful and less changeful than his philosophical development.[1] Born in Koenigsberg in 1724, the son of J.G. Cant, a saddler of Scottish descent, his home and school training were both strict and of a markedly religious type. He was educated at the university of his native city, and for nine years, from 1746 on, filled the place of a private tutor. In 1755 he became Docent, in 1770 ordinary professor in Koenigsberg, serving also for six years of this time as under-librarian. He seldom left his native city and never the province. The clearness which marked his extremely popular lectures on physical geography and anthropology was due to his diligent study of works of travel, and to an unusually acute gift of observation, which enabled him to draw from his surroundings a comprehensive knowledge of the world and of man. He ceased lecturing in 1797, and in 1804 old age ended a life which had always, even in minute detail, been governed by rule. A man of extreme devotion to duty, particularity, and love of truth, and an amiable, bright, and witty companion, Kant belongs to the acute rather than to the profound thinkers. Among his manifold endowments the tendency to combination and the faculty of intuition (as the Critique of Judgment especially shows) are present to a noticeable degree, yet not so markedly as the power of strict analysis and subtle discrimination. So that, although a mediating tendency is rightly regarded as the distinguishing characteristic of the Kantian thinking, it must also be remembered that synthesis is everywhere preceded by a mighty work of analysis, and that this still exerts its power even after the adjustment is complete. Thus Kant became the energetic defender of a qualitative view of the world in opposition to the quantitative view of Leibnitz, for which antitheses (e.g., sensation and thought, feeling and cognition, good and evil, duty and inclination) fade into mere differences of degree.

[Footnote 1: The following have done especially valuable service in the investigation of the development of Kant's doctrine: Paulsen (Versuch einer Entwickelungsgeschichte der Kantischen Erkenntnisstheorie, 1875), B. Erdmann, Vaihinger, and Windelband. Besides Hume and Leibnitz, Newton, Locke, Shaftesbury, Rousseau, and Wolff exercised an important influence on Kant.]

In the beginning of this chapter we have indicated how the new ideal of knowledge, under whose banner Kant brought about a reform of philosophy, grew out of the conflict between the rationalistic (dogmatic) and the empirical (skeptical) systems. This combines the Baconian ideal of the extension of knowledge with the Cartesian ideal of certainty in knowledge. It is synthetic judgments alone which extend knowledge, while analytic judgments are explicative merely.[1] A priori judgments alone are perfectly certain, absolutely universal, and necessarily valid; while a posteriori judgments are subjectively valid merely, lack necessity, and, at best, yield only relative universality.[2] All analytic judgments are a priori, all empirical or a posteriori judgments are synthetic. Between the two lies the object of Kant's search. Do synthetic judgments a priori exist, and how are they possible?

[Footnote 1: "All bodies are extended" is an analytic judgment; "all bodies possess weight," a synthetic judgment. The former explicates the concept of the subject by bringing into notice an idea already contained in it and belonging to the definition as a part thereof; it is based on the law of contradiction: an unextended body is a self-contradictory concept. The latter, on the contrary, goes beyond the concept of the subject and adds a predicate which had not been thought therein. It is experience which teaches us that weight is joined to matter, a fact which cannot be derived from the concept of matter. Almost all mathematical principles are synthetic, and here, as will be shown, it is not experience but "pure intuition" which permits us to go beyond the concept and add a new mark to it.]

[Footnote 2: The Scholastics applied the term a priori to knowledge from causes (from that which precedes), and a posteriori to knowledge from effects. Kant, following Leibnitz and Lambert, uses the terms to designate the antithesis, knowledge from reason and knowledge from experience. An a priori judgment is a judgment obtained without the aid of experience. When the principle from which it is derived is also independent of experience it is absolutely a priori, otherwise it is relatively a priori.]

Two sciences discuss the how, and a third the if of such judgments, which, at the same time, are ampliative and absolutely universal and necessary. The first two sciences are pure mathematics and pure natural science, of which the former is protected against doubt concerning its legitimacy by its evident character, and the latter, by the constant possibility of verification in experience; each, moreover, can point to the continuous course of its development. All this is absent in the third science, metaphysics, as science of the suprasensible, and to its great disadvantage. Experiential verification is in the nature of things denied to a presumptive knowledge of that which is beyond experience; it lacks evidence to such an extent that there is scarcely a principle to be found to which all metaphysicians assent, much less a metaphysical text-book to compare with Euclid; there is so little continuous advance that it is rather true that the later comers are likely to overthrow all that their predecessors have taught. In metaphysics, therefore, which, it must be confessed, is actual as a natural tendency, the question is not, as in the other two sciences, concerning the grounds of its legitimacy, but concerning this legitimacy itself. Mathematics and pure physics form synthetic judgments a priori, and metaphysics does the same. But the principles of the two former are unchallenged, while those of the third are not. In the former case the subject for investigation is, Whence this authority? in the latter case, Is she thus authorized?

Thus the main question, How are synthetic judgments a priori possible? divides into the subordinate questions, How is pure mathematics possible? How is pure natural science possible, and, How is metaphysics (in two senses: metaphysics in general, and metaphysics as science) possible? The Transcendental Aesthetic (the critique of sensibility or the faculty of intuition) answers the first of these questions; the Transcendental Analytic (the critique of the understanding), the second; and the Transcendental Dialectic (the critique of "reason" in the narrower sense) and the Transcendental Doctrine of Method (Methodenlehre), the third. The Analytic and the Dialectic are the two parts of the Transcendental "Logic" (critique of the faculty of thought), which, together with the Aesthetic, forms the Transcendental "Doctrine of Elements" (Elementarlehre), in contrast to the Doctrine of Method. The Critique of Pure Reason follows this scheme of subordinate division, while the Prolegomena co-ordinates all four parts in the manner first mentioned.

Let us anticipate the answers. Pure mathematics is possible, because there are pure or a priori intuitions (space and time), and pure natural science or the metaphysics of phenomena, because there are a priori concepts (categories) and principles of the pure understanding. Metaphysics as a presumptive science of the suprasensible has been possible in the form of unsuccessful attempts, because there are Ideas or concepts of reason which point beyond experience and look as though knowable objects were given through them; but as real science it is not possible, because the application of the categories is restricted to the limits of experience, while the objects thought through the Ideas cannot be sensuously given, and all assumed knowledge of them becomes involved in irresolvable contradictions (antinomies). On the other hand, a science is possible and necessary to teach the correct use of the categories, which may be applied to phenomena alone, and of the Ideas, which may be applied only to our knowledge of things (and our volition), and to determine the origin and the limits of our knowledge—that is to say, a transcendental philosophy. In regard to metaphysics (knowledge from pure reason), then, this is the conclusion reached: Rejection of transcendent metaphysics (that which goes beyond experience), recognition and development of immanent metaphysics (that which remains within the limits of possible experience). It is not possible as a metaphysic of things in themselves; it is possible as a metaphysic of nature (of the totality of phenomena), and as a metaphysic of knowledge (critique of reason).

The interests of the reason are not exhausted, however, by the question, What can we know? but include two further questions, What ought we to do? and, What may we hope? Thus to the metaphysics of nature there is added a metaphysics of morals, and to the critique of theoretical reason, a critique of practical reason or of the will, together with a critique of religious belief. For even if a "knowledge" of the suprasensible is denied to us, yet "practical" grounds are not wanting for a sufficiently certain "conviction" concerning God, freedom, and immortality.

After carrying the question of the possibility of synthetic judgments a priori from the knowledge of nature over to the knowledge of our duty, Kant raises it, in the third place, in regard to our judgment concerning the subjective and objective purposiveness of things, or concerning their beauty and their perfection, and adds to his critique of the intellect and the will a critique of the faculty of aesthetic and teleological judgment.

The Kantian philosophy accordingly falls into three parts, one theoretical, one practical (and religious), one aesthetic and teleological.

* * * * *

Before advancing to our account of the first of these parts, a few preliminary remarks are indispensable concerning the presuppositions involved in Kant's critical work and on the method which he pursues. The presuppositions are partly psychological, partly (as the classification of the forms of judgment and inference, and the twofold division of judgments) logical, either in the formal or the transcendental sense, and partly metaphysical (as the thing in itself). Kant takes the first of these from the psychology of his time, by combining the Wolffian classification of the faculties with that of Tetens, and thus obtains six different faculties: lower (sensuous) and higher (intellectual) faculties of cognition, of feeling, and of appetition; or sensibility (the capacity for receiving representations through the way in which we are affected by objects), understanding (the faculty of producing representations spontaneously and of connecting them); the sensuous feelings of pleasure and pain, taste; desire, and will. The understanding in the wide sense is equivalent to the higher faculty of cognition, and divides further into understanding in the stricter sense (faculty of concepts), judgment (faculty of judging), and reason (faculty of inference). Of these the first gives laws to the faculty of cognition or to nature, the second laws to taste, and the third laws to the will.

The most important of the fundamental assumptions concerns the relation, the nature, and the mission of the two faculties of cognition. These do not differ in degree, through the possession of greater or less distinctness—for there are sensuous representations which are distinct and intellectual ones which are not so—but specifically: Sensibility is the faculty of intuitions, understanding the faculty of concepts. Intuitions are particular, concepts general representations. The former relate to objects directly, the latter only indirectly (through the mediation of other representations). In intuition the mind is receptive, in conception it acts spontaneously. "Through intuitions objects are given to us; through concepts they are thought." It results from this that neither of the two faculties is of itself sufficient for the attainment of knowledge, for cognition is objective thinking, the determination of objects, the unifying combination or elaboration of a given manifold, the forming of a material content. Rationalists and empiricists alike have been deceived in regard to the necessity for co-operation between the senses and the understanding. Sensibility furnishes the material manifold, which of itself it is not able to form, while the understanding gives the unifying form, to which of itself it cannot furnish a content. "Intuitions without concepts are blind" (formless, unintelligible), "concepts without intuitions are empty" (without content). In the one case, form and order are wanting; in the other, the material to be formed. The two faculties are thrown back on each other, and knowledge can arise only from their union.

A certain degree of form is attained in sense, it is true, since the chaos of sensations is ordered under the "forms of intuition," space and time, which are an original possession of the intuiting subject, but this is not sufficient, without the aid of the understanding, for the genesis of knowledge. In view of the a priori nature of space and time, though without detraction from their intuitive character (they are immediate particular representations), we may assign pure sensibility to the higher faculty of cognition and speak of an intuiting reason.

The forms of intuition and of thought come from within, they lie ready in the mind a priori, though not as completed representations. They are functions, necessary actions of the soul, for the execution of which a stimulus from without, through sensations, is necessary, but which, when once this is given, the soul brings forth spontaneously. The external impulse merely gives the soul the occasion for such productive acts, while their grounds and laws are found in its own nature. In this sense Kant terms them "originally acquired," and in the Introduction to the Critique of Pure Reason declares that although it is indubitable that "all our knowledge begins with experience (impressions of sense), yet it does not all arise from experience." That a representation or cognition is a priori[1] does not mean that it precedes experience in time, but that (apart from the merely exciting, non-productive stimulation through impressions already mentioned) it is independent of all experience, that it is not derived or borrowed from experience.

[Footnote 1: The terms a priori representation and pure representation (concept, intuition) are equivalent; but in judgments, on the other hand, there is a distinction. A judgment is a priori when the connection takes place independently of experience, no matter whether the concepts connected are a priori or not. If the former is the case the a priori judgment is pure (mixed with nothing empirical); if the latter, it is mixed.]

The material of intuition and thought is given to the soul, received by it; it arises through the action of objects upon the senses, and is always empirical. Intuition is the only organ of reality; in sensation the presence of a real object as the cause of the sensation is directly revealed. When Kant's transcendental idealism was placed by a reviewer on a level with the empirical idealism of Berkeley, which denies the existence of the external world, he distinctly asserted that it had never entered his mind to question the reality of external things. Further, after the existence of real things affecting the senses had been transformed in his mind from a basis of the investigation into an object of inquiry, he endeavored to defend this assumption (which at first he had naively borrowed from the realism of pre-scientific thought) by arguments, but without any satisfactory result.[1]

[Footnote 1: The task of confirming the existence of things in themselves changes under his hands into another, that of proving the existence of external phenomena. "That external objects are real as representations" Berkeley had never disputed.]

On the basis of the inseparability of sensibility and understanding the ideal of knowledge—an extension of knowledge to be attained by a priori means (p. 333)—experiences a remarkable addition in the position that the rational synthesis thus obtained must be a knowledge of reality, must be applied to matter given in intuition. To the question, "How are synthetic judgments a priori possible?" is joined a second equally legitimate inquiry, "How do they become objectively valid, or applicable to objects of experience?" The principle from which their validity is proved—they are applicable to objects of experience because without them experience would not be possible, because they are conditions of experience—like the criterion of apriority (strict universality and necessity), is one of the noetic assumptions of the critical theory.[1]

[Footnote 1: Cf. Vaihinger, Kommentar, i. pp. 425-430.]

Inasmuch as its investigation relates to the conditions of experience the Kantian criticism follows a method which it itself terms transcendental. Heretofore, when the metaphysical method had been adopted, the object had been the suprasensible; and when knowledge had been made the object of investigation, the method followed had been empirical, psychological. Kant had the right to consider himself the creator of noetics, for he showed it the transcendental point of view. Knowledge is an object of experience, but its conditions are not. The object is to explain knowledge, not merely to describe it psychologically,—to establish a new science of knowledge from principles, from pure reason. That which lies beyond experience is sealed from our thought; that which lies on this side of it is still uninvestigated, though capable and worthy of investigation, and in extreme need thereof. Criticism forbids the transcendent use of reason (transcending experience); it permits, demands, and itself exercises the transcendental[1] use of it, which explains an experiential object, knowledge, from its conditions, which are not empirically given.

[Footnote A: Kant applies the term transcendental to the knowledge (the discovery, the proof) of the a priori factor and its relation to objects of experience. Unfortunately he often uses the same word not only to designate the a priori element itself, but also as a synonym for transcendent. In all three cases its opposite is empirical, namely, empirico-psychological investigation by observation in distinction from noetical investigation from principles; empirical origin in distinction from an origin in pure reason, and empirical use in distinction from application beyond the limits of experience.]

There is, apparently, a contradiction between the empiristic result of the Critique of Reason (the limitation of knowledge to objects of experience) and its rationalistic proofs (which proceed metaphysically, not empirically), and, in fact, a considerable degree of opposition really exists. Kant argues in a metaphysical way that there can be no metaphysics. This contradiction is solved by the distinction which has been mentioned between that which is beyond, and that which lies within, the boundary of experience. That metaphysic is forbidden which on the objective side soars beyond experience, but that pure rational knowledge is permissible and necessary which develops from principles the grounds of experiential knowledge existing in the subject. In the Kantian school, however, these complementary elements,—empirical result, transcendental or metaphysical, properly speaking, pro-physical method,—were divorced, and the one emphasized, favored, and further developed at the expense of the other. The empiricists hold to the result, while they either weaken or completely misunderstand the rationalism of the method: the a priori factor, says Fries, was not reached by a priori, but by a posteriori, means, and there is no other way by which it could have been reached. The constructive thinkers, Fichte and his successors, adopt and continue the metaphysical method, but reject the empirical result. Fichte's aim is directed to a system of necessary, unconscious processes of reason, among which, rejecting the thing in itself, he includes sensation. According to Schelling nature itself is a priori, a condition of consciousness. This discrepancy between foundation and result continues in an altered form even among contemporary thinkers—as a discussion whether the "main purpose" of Criticism is to be found in the limitation of knowledge to possible experience, or the establishment of a priori elements—though many, in adherence to Kant's own view, maintain that the metaphysics of knowledge and of phenomena (immanent rationalism) is the only legitimate metaphysics.

%1. Theory of Knowledge.

(a) The Pure Intuitions (Transcendental Aesthetic).%—The first part of the Critique of Reason, the Transcendental Aesthetic, lays down the position that space and time are not independent existences, not real beings, and not properties or relations which would belong to things in themselves though they were not intuited, but forms of our intuition, which have their basis in the subjective constitution of our, the human, mind. If we separate from sensuous intuition all that the understanding thinks in it through its concepts, and all that belongs to sensation, these two forms of intuition remain, which may be termed pure intuitions, since they can be considered apart from all sensation. As subjective conditions (lying in the nature of the subject) through which alone a thing can become an object of intuition for us, they precede all empirical intuitions or are a priori.

Space and time are neither substantial receptacles which contain all that is real nor orders inhering in things in themselves, but forms of intuition. Now all our representations are either pure or empirical in their origin, and either intuitive or conceptual in character. Kant advances four proofs for the position that space and time are not empirical and not concepts, but pure intuitions: (1) Time is not an empirical concept which has been abstracted from experience. For the coexistence or succession of phenomena, i.e., their existence at the same time or at different times (from which, as many believe, the representation of time is abstracted), itself presupposes time—a coexistence or succession is possible only in time. It is no less false that space is abstracted from the empirical space relations of external phenomena, their existence outside and beside one another, or in different places, for it is impossible to represent relative situation except in space. Therefore experience does not make space and time possible; but space and time first of all make experience possible, the one outer, the other inner experience. They are postulates of perception, not abstractions from it. (2) Time is a necessary representation a priori. We can easily think all phenomena away from it, but we cannot remove time itself in view of phenomena in general; we can think time without phenomena, but not phenomena without time. The same is true of space in reference to external objects. Both are conditions of the possibility of phenomena. (3) Time is not a discursive or general concept. For there is but one time. And different times do not precede the one time as the constituent parts of which it is made up, but are mere limitations of it; the part is possible only through the whole. In the same way the various spaces are only parts of one and the same space, and can be thought in it alone. But a representation which can be given only by a single object is a particular representation or an intuition. Because, therefore, of the oneness of space and time, the representation of each is an intuition. The a priori, immediate intuition of the one space is entirely different from the empirical, general conception of space, which is abstracted from the various spaces. (4) Determinate periods of time arise by limitation of the one, fundamental time. Consequently this original time must be unlimited or infinite, and the representation of it must be an intuition, not a concept. Time contains in itself an endless number of representations (its parts, times), but this is never the case with a generic concept, which, indeed, is contained as a partial representation in an endless number of representations (those of the individuals having the same name), and, consequently, comprehends them all under itself, but which never contains them in itself. The general concept horse is contained in each particular representation of a horse as a general characteristic, and that of justice in each representation of a definite just act; time, however, is not contained in the different times, but they are contained in it. Similarly the relation of infinite space to the finite spaces is not the logical relation of a concept to examples of it, but the intuitive relation of an unlimited whole to its limited parts.

The Prolegomena employs as a fifth proof for the intuitive character of space, an argument which had already appeared in the essay On the Ultimate Ground of the Distinction of Positions in Space. There are certain spatial distinctions which can be grasped by intuition alone, and which are absolutely incapable of comprehension through the understanding—for example, those of right and left, above and below, before and behind. No logical marks can be given for the distinction between the object and its image in the mirror, or between the right ear and the left. The complete description of a right hand must, in all respects (quality, proportionate position of parts, size of the whole), hold for the left as well; but, despite the complete similarity, the one hand cannot be exactly super-imposed on the other; the glove of the one cannot be worn on the other. This difference in direction, which has significance only when viewed from a definite point, and the impossibility mentioned of a congruence between an object (right hand) and its reflected image (left hand) can be understood only by intuition; they must be seen and felt, and cannot be made clear through concepts, and, consequently, can never be explained to a being which lacks the intuition of space.

In the "transcendental" exposition of space and time Kant follows this "metaphysical" exposition, which had to prove their non-empirical, and non-discursive, hence their a priori and intuitive, character, with the proof that only such an explanation of space and time could make it conceivable how synthetic cognitions a priori can arise from them. The principles of mathematics are of this kind. The synthetic character of geometrical truths is explained by the intuitive nature of space, their apodictic character by its apriority, and their objective reality or applicability to empirical objects by the fact that space is the condition of (external) perception. The like is true of arithmetic and time.

If space were a mere concept, no proposition could be derived from it which should go beyond the concept and extend our knowledge of its properties. The possibility of such extension or synthesis in mathematics depends on the fact that spatial concepts can always be presented or "constructed" in intuition. The geometrical axiom that in the triangle the sum of two sides is greater than the third is derived from intuition, by describing the triangle in imagination or, actually, on the board. Here the object is given through the cognition and not before it.—If space and time were empirical representations the knowledge obtained from them would lack necessity, which, as a matter of fact, it possesses in a marked degree. While experience teaches us only that something is thus or so, and not that it could not be otherwise, the axioms, (space has only three dimensions, time only one; only one straight line is possible between two points), nay, all the propositions of mathematics are strictly universal and apodictically certain: we are entirely relieved from the necessity of measuring all triangles in the world in order to find out whether the sum of their angles is equal to two right angles, and we do not need, as in the case of judgments of experience, to add the limitation, so far as it is yet known there are no exceptions to this rule. The apriority is the ratio essendi of the strict necessity involved in the "it must be so" (des Soseinmuessens), while the latter is the ratio cognoscendi of the former. Now since the necessity of mathematical judgments can only be explained through the ideality of space, this doctrine is perfectly certain, not merely a probable hypothesis.—The validity of mathematical principles for all objects of perception, finally, is based on the fact that they are rules under which alone experience is possible for us. It should be mentioned, further, that the conceptions of change and motion (change of place) are possible only through and in the representation of time. No concept could make intelligible the possibility of change, that is, of the connection of contradictory predicates in one and the same thing, but the intuition of succession easily succeeds in accomplishing it.

The argument is followed by conclusions and explanations based upon it; (1) Space is the form of the outer, time of the inner, sense. Through the outer sense external objects are given to us, and through the inner sense our own inner states. But since all representations, whether they have external things for their objects or not, belong in themselves, as mental determinations, to our inner state, time is the formal condition of all phenomena in general, directly of internal (psychical) phenomena, and, thereby, indirectly of external phenomena also. (2) The validity of the relations of space and time cognizable a priori is established for all objects of possible experience, but is limited to these. They are valid for all phenomena (for all things which at any time may be given to our senses), but only for these, not for things as they are in themselves. They have "empirical reality, but, at the same time, transcendental ideality." As external phenomena all things are beside one another in space, and all phenomena whatever are in time and of necessity under temporal relations; in regard to all things which can occur in our experience, and in so far as they can occur, space and time are objectively, therefore empirically, real. But they do not possess absolute reality (neither subsistent reality nor the reality of inherence); for if we abstract from our sensuous intuition both vanish, and, apart from the subject (N.B., the transcendental subject, concerning which more below), they are naught. It is only from man's point of view that we can speak of space, and of extended, moveable, changeable things; for we can know nothing concerning the intuitions of other thinking beings, we have no means of discovering whether they are bound by the same conditions which limit our intuitions, and which for us are universally valid. (3) Nothing which is intuited in space is a thing in itself. What we call external objects are nothing but mere representations of our sensibility, whose true correlative, the thing in itself, cannot be known by ever so deep penetration into the phenomenon; such properties as belong to things in themselves can never be given to us through the senses. Similarly nothing that is intuited in time is a thing in itself, so that we intuit ourselves only as we appear to ourselves, and not as we are.

The merely empirical reality of space and time, the limitation of their validity to phenomena, leaves the certainty of knowledge within the limits of experience intact; for we are equally certain of it, whether these forms necessarily belong to things in themselves, or only to our intuitions of things. The assertion of their absolute reality, on the other hand, involves us in sheer absurdities (that is, it necessitates the assumption of two infinite nonentities which exist, but without being anything real, merely in order to comprehend all reality, and on one of which even our own existence would be dependent), in view of which the origin of so peculiar a theory as the idealism of Berkeley appears intelligible. The critical theory of space and time is so far from being identical with, or akin to, the theory of Berkeley, that it furnishes the best and only defense against the latter. If anyone assumes the absolute or transcendental reality of these forms, it is impossible for him to prevent everything, including even our own existence, from being changed thereby into mere illusion. But the critical philosopher is far from degrading bodies to mere illusion; external phenomena are just as real for him as internal phenomena, though only as phenomena, it is true, as (possible) representations.

Phenomenon and illusion are not the same. The transcendental distinction between phenomena and things in themselves must not be confused with the distinction common to ordinary life and to physics, in accordance with which we call the rainbow a mere appearance (better, illusion), but the combination of sun and rain which gives rise to this illusion the thing in itself, as that which in universal experience and in all different positions with respect to the senses, is thus and not otherwise determined in intuition, or that which essentially belongs to the intuition of the object, and is valid for every human sensibility (in antithesis to that which only contingently belongs to it, and is valid only for a special position or organization of this or that sense). Similarly an object always appears to grow smaller as its distance increases, while in itself it is and remains of some fixed size. And this use of words is perfectly correct, in the physical or empirical sense of "in itself"; but in the transcendental sense the raindrops, also, together with their form and size, are themselves mere phenomena, the "in itself" of which remains entirely unknown to us. Kant, moreover, does not wish to see the subjectivity of the forms of intuition placed on a level with the subjectivity of sensations or explained by this, though he accepts it as a fact long established. The sensations of color, of tone, of temperature are, no doubt, like the representation of space in that they belong only to the subjective constitution of the sensibility, and can be attributed to objects only in relation to our senses. But the great difference between the two is that these sense qualities may be different in different persons (the color of the rose may seem different to each eye), or may fail to harmonize with any human sense; that they are not a priori in the same strict sense as space and time, and consequently afford no knowledge of the objects of possible experience independently of perception; and that they are connected with the phenomenon only as the contingently added effects of a particular organization, while space, as the condition of external objects, necessarily belongs to the phenomenon or intuition of them. It is through space alone that it is possible for things to be external objects for us. The subjectivity of sensation is individual, while that of space and time is general or universal to mankind; the former is empirical, individually different, and contingent, the latter a priori and necessary. Space alone, not sensation, is a conditio sine qua non of external perception. Space and time are the sole a priori elements of the sensibility; all other sensuous concepts, even motion and change, presuppose perception; the movable in space and the succession of properties in an existing thing are empirical data.

In confirmation of the theory that all objects of the senses are mere phenomena, the fact is adduced that (with the exception of the will and the feelings, which are not cognitions) nothing is given us through the senses but representations of relations, while a thing in itself cannot be known by mere relations. The phenomenon is a sum total of mere relations. In regard to matter we know only extension, motion, and the laws of this motion or forces (attraction, repulsion, impenetrability), but all these are merely relations of the thing to something, else, that is, external relations. Where is the inner side which underlies this exterior, and which belongs to the object in itself? This is never to be found in the phenomenon, and no matter how far the observation and analysis of nature may advance (a work with unlimited horizons!) they reach nothing but portions of space occupied by matter and effects which matter exercises, that is, nothing beyond that which is comparatively internal, and which, in its turn, consists of external relations. The absolutely inner side of matter is a mere fancy; and if the complaint that the "inner side" of things is concealed from us is to mean that we do not comprehend what the things which appear to us may be in themselves, it is unjust and irrational, for it demands that we should be able to intuit without senses, in other words, that we should be other than men. The transcendent questions concerning the noumenon of things are unanswerable; we know ourselves, even, only as phenomena! A phenomenon consists in nothing but the relation of something in general to the senses.