Immanuel Kant was born in Königsberg in 1724, and he died in 1804. The outward course of his life was uneventful, and its main interest lies in the story of his philosophical development. He was the son of a humble tradesman of Scottish descent. His mother was a woman of piety and intelligence. The influence of his home and of his early training in a school presided over by a leader of the Pietists, did much to foster that combination of moral intensity and sobriety of understanding which formed the basis of his character. He entered the University of his native town at the age of sixteen as a student of philosophy and mathematics. In 1755, in his thirty-first year, he became a college tutor. His first work was an essay on Thoughts on the True Estimate of Motive Force. In the year 1770, at the age of forty-six, he became Professor of Logic and Metaphysics. He received calls from various other universities, which, however, he declined. In 1797, in his seventy-fifth year, he ceased to lecture on account of the infirmities of age. He lived a simple, frugal life. Though unmarried, he enjoyed the society of congenial friends.
Though he never travelled beyond his native province, he was an extensive reader of travels, and had an accurate knowledge of geography. He was a man of upright character, of great modesty and kindliness of disposition. He was most methodical in all his ways. He rose at 5 a.m., worked, lectured, and wrote till 1 p.m., when he dined. Exactly at half-past four he went for his walk, always the same, which was called after him the "Philosopher's Walk." Heine humorously remarked that the good people of Königsberg set their watches when he appeared. He was an interesting lecturer, and had much sympathy with the young life of the University. He died in his 80th year in 1804.
The most important of his early works was A Natural History and Theory of the Heavens, in which he extends Newton's mechanical theory of the actual planetary system, to explain the genesis of that system, anticipating many of the ideas which were afterwards developed by Laplace. After 1762 his thoughts tended more to philosophy proper, and particularly to the criticism of the faculties of man with which his name is chiefly associated in the history of philosophy. He has, however, given an impulse to thought in almost every department, which has lasted for more than a century and is not yet spent. Not only idealists like Fichte, Schelling, and Hegel, but realists like Herbart and Lotze owe to him their inspiration. As has been said, "whatever metal of speculation is anywhere turned now, the ore of it is Kant's."
The principal works of Kant, which form the constituent parts of his System, Metaphysical and Ethical, are:
The Critique of Pure Reason, published in 1781; the Second Edition, corrected, in 1787.
Foundation of the Metaphysics of Ethics—1785.
Critique of Practical Reason—1788.
Critique of Judgment—1790.
Religion within the Bounds of Pure Reason—1794.
Before entering upon a detailed exposition of Kant's philosophy, it will be desirable to offer a brief indication of its aim and scope. There are, therefore, two preliminary points which claim our attention: the purpose and results of Kant's speculation.
1. The Purpose. Previous to Kant's time, two lines of speculation—those of Locke and Leibnitz—though so different in character and principles, led to the same results —the severance of thought and reality. The old question as to whether we receive our knowledge from without or bring it forth by the activity of our own minds from within, whether our cognition is the product of sensation or of pure thought, divided the philosophical world into two camps. On the one side the Empirical school maintained that all our knowledge comes from experience alone, and that the mind is passive; on the other hand, the Rationalist school held that the mind alone is the source of cognition, and that we know nothing but our own ideas. Each sought to solve the opposition between mind and matter by denying one of the factors. Both were equally one-sided. Both failed. The empiricism of Locke issued in the scepticism of Hume; the individualism of Leibnitz and Wolff, in the dogmatic assumption of an external harmony.
An attempt, therefore, is made by Kant to reconcile the two extremes of Realism and Idealism.
Kant had been educated in the Wolffian philosophy, and was for a time an adherent of it. But he could not long rest satisfied with its assumptions. Wolff assumed that by the employment of abstract principles he could reach an ultimate knowledge of all reality. But Kant found that the mere application of analytic propositions, such as are used in mathematics, furnished the mind with no contents. He turned, therefore, to empiricism. But a study of Locke's sensationalism soon showed him that Hume's deductions were correct, and that unless the mind possessed some faculty of synthesis, some unifying principle, all we could know would be a series of unconnected sensations; and that, therefore, scepticism, despair of reaching all truth, was the conclusion to which we were shut up. Again he felt that this could not be the ultimate explanation of things.
"It was the reflection on David Hume," he says in a famous passage, "that several years ago first broke my dogmatic slumber and gave a completely new direction to my enquiries in the field of speculative philosophy."
The question regarding causality according to which Hume maintained that all that we see is the mere succession of isolated sensations without any causal connection, suggested to Kant the more general question—how propositions which are based, not on experience but on pure thought, can, nevertheless, possess validity for the world of objects. The question suggests to him the propriety of reversing the order which was supposed to obtain between the mind and its-objects—a revolution in mental procedure which Kant compares to that which was effected by Copernicus in astronomy. Hitherto it had been assumed that all our knowledge must adapt itself to the objects. "Suppose," he says, "we try now whether better success may not attend us in the problems of metaphysics, if we assume objects to be under the necessity of adapting themselves to the nature of our cognitions, a method which clearly would better agree with the avowed aim of metaphysics, to determine the nature of objects, a priori, or before they are actually presented" (Krit. d. r. Vernunft, Pref. 2nd Ed.).
This is really the fundamental thought of Kant's system. It is not in things that we are to look for the explanation of the laws of the mind. On the contrary, it is in the mind that we must seek the reason of things. It is here that we see the idealism of Kant, an idealism, however, different from all former kinds. The mind legislates over things. We create the world: it is the product of the laws of our own understanding. The mind supplies the form of knowledge, but not its matter. This matter in itself we cannot attain to, for we can only know what has passed through the forms of sense.
The question, therefore, which Kant is led to ask is no longer whether the idealists were right or the empiricists were right, but what part does the mind play in the constitution of what we call knowledge? But it was not by a fusion of both views that Kant sought to reconcile their opposition. His significance lies in directing speculation to an entirely new problem—viz. the nature and origin of knowledge itself.
It is the task of Kant, therefore, to set aside all dogmatic presuppositions and to deal with the preliminary question —What and how does the mind know? He will subject reason itself to a searching investigation, that he may discover its constitution and its factors. He will examine the origin and scope of our knowledge, find out its sources, and fix its limits. Hence Kant designates his standpoint "criticism," and the work which undertakes this task is called the Critique of Pure Reason. It is also called by him "Transcendental," because it has "to do not so much with the objects, as with our knowing of the objects, in so far as there is any possibility of an a priori knowledge of them."
2. Results. The object, then, which Kant proposes is a criticism of human knowledge with a view to determining its nature and its limits. There is a twofold necessity for such criticism. The first is the failure of philosophy hitherto to arrive at any definite conclusions in regard to those very questions which the mind cannot but ask, and which it seeks most of all to understand. Scepticism has not quenched the insatiable longings of reason to solve those problems as to the Being of God, human freedom, and the order of the world which constantly recur to the mind. "It is vain," says Kant, "to strive after an artificial indifference towards enquiries whose object can never be indifferent to the nature of man." The necessity of this inquiry is felt, secondly, when we consider how naturally we are led by the extension of our empirical knowledge to speculate about that which is beyond experience and to make assumptions which experience cannot verify.
The conclusion to which Kant comes is, not that metaphysics in itself is impossible, "for some such disposition of the human mind must exist as soon as reason awakes to the exercise of its powers," but that the ideas with which metaphysics deals, being objects of a supersensible world unconditioned by the forms of the mind, cannot be proved by the speculative reason in the same way as the objects of other sciences can be proved. We can only know phenomena, that is, things as they are modified and transformed for us by the action of the mind itself. "The unconditioned cannot be thought without contradiction." "These objects which reason thinks and necessarily thinks, but which are not given in experience, or at least as reason thinks them," cannot be cognised or proved in the same way as objects given in experience. A purely scientific knowledge of the soul, of God, and of the unity of the world is not available.
Yet these ideas are not to be regarded as false or illusory though speculative reason cannot verify them. They are there: they can be thought, and they press for recognition. It is true they have no phenomena corresponding to them which the forms of our understanding can seize upon. But they are in our consciousness. There must be another way of vindicating them. For, after all, reason is one, and the ideas of reason must have a purpose for man not less than the objects of experience. The interests of philosophy and of life Kant felt are not exhausted by the question, what or how can we know? We must also inquire, what shall we do and what may we hope? Hence Kant is convinced that by means of our faculty of willing we can press into the supersensuous world, which is closed to speculative reason. "After we have thus denied the power of speculative reason to make any progress in the sphere of the supersensible, it still remains for our consideration whether data do not exist in practical cognition which may enable us to determine the conception of the unconditioned, to rise beyond the limits of all possible experience from a practical point of view, and thus to satisfy the great ends of metaphysics" (Krit. d. r. Vernunft, Pref. 2nd Ed.).
On this account Kant follows up the Critique of Pure Reason with an examination of the ethical demands and moral faculties which constitute the basis of his moral theory—which he calls the Critique of Practical Reason. The ideas of freedom, the soul, and God, which the Critique of Pure Reason postulated, but could not prove, Practical Reason restores to their place of authority in the life of man. Finally, in a third treatise, the Critique of Judgment, he endeavours to indicate the point in which the theoretic and practical views of the world unite.
We may now proceed to a more particular exposition of the Kantian philosophy. And as Kant himself divides all the faculties of the soul into three—thinking, feeling, and willing—we may follow him in dividing his doctrine into a theoretic, a practical, and an aesthetic part. The theoretic part deals with the principles of cognition and reason proper. The practical deals with the principles of the will. The aesthetic,—in so far as it is a theory of the sensations of pleasure and pain, and of the feelings generally—as mediating between the reason and the will, is a faculty of judgment. Hence we have the three great critiques, of Pure Reason, of Practical Reason, and of Judgment.