But it must not be supposed that Kant regards faith as something less than knowledge. It is, indeed, in his view a higher form of certainty guaranteed by the very consciousness of self. If Kant had been true to the suggestion which he himself makes, that the consciousness of self involves the knowledge of the whole world of things, he would have seen that the solution of the antinomies, which he set up at the close of the Critique of Pure Reason, is to be found, not in emphasizing the distinction between phenomena and things in themselves, but rather in the very perception of the unity of the self and the world of objects which self-consciousness involves. Kant has developed his practical philosophy partly in his Metaphysics of Morals, partly in his Critique of Practical Reason, and partly in the Metaphysical Foundations of the Theory of Rights and Virtues. The Metaphysics of Ethics treats of the laws of Morality; the Practical Reason, of the faculty for it; and the Metaphysical Foundations, of particular duties. In the first, Kant lays down the principle of the Categorical Imperative, the supreme law of the moral life. In the second, he inquires as to whether man has a faculty by which he is able to fulfil the commands of the moral law. After the analogy of the Critique of Pure Reason, the Critique of Practical Reason is divided into two parts; an Analytic, which analyses the notion of duty as the dictate of a higher faculty which acts independently of sense in obedience to its own law; and a Dialectic, which deals with the antinomies which arise from the conflict between the authority of pure reason and the instigations of sense. Under this head he treats of the Summum Bonum, the supreme good or virtue which Practical Reason prescribes, and the difficulties and conditions of attaining it.
Again, just as the Critique of Practical Reason is divided into two parts, so The Metaphysical Foundations of the Theory of Virtue has two parts; the first of which has to do with Jurisprudence, or the laws and constitution of the State; and the second, with individual morals, or the duties of man to himself and to others.
In his treatise of the Critique of Judgment, Kant develops a teleological conception of the Universe, and thereby seeks to unite in a higher unity, theoretic and practical reason, the ideas of nature and spirit, of necessity and freedom, in a realm of feeling which finds expression in the consciousness of the beautiful. Here, then, Kant treats of Art as embodied in the beautiful and the sublime, as well as of the general idea of a teleological purpose in the universe.
Finally, Kant's religious views with regard to God's attributes and man's relation towards Him, with regard to Christianity and the Church's constitution and ordinances, are contained in his remarkable and somewhat neglected work, Religion within the Limits of Pure Reason. We may now proceed to a more detailed account of these various subjects.
Kant's Doctrine of Morality, Kant's theory of morals was an attempt to reconcile the two opposing ethical principles which were current in the eighteenth century. On the one side were the Realists, who treated man as a merely natural being, and, accordingly, demanded a pursuance of the natural impulses of his nature, some of whom, like Hutcheson, regarded them as benevolent, and others, like Helvetius, as selfish. Opposed to these, on the other side, were the Idealists, who conceived that man must be ruled only by his idea of goodness or perfection. Both theories, though opposed in their methods, united in regarding happiness as the end of life, the one the happiness of sensuous enjoyment, and the other that of self-sufficiency. Both set an end outside of the man himself as the basis of their ethical doctrine. Kant at once seeks to take a higher standpoint, above both, and to show that the law of our moral life must not rest upon ulterior ends at all, but must spring from an inherent rational principle. Morality must be disinterested, and the law which governs man's life must be self-originating and not subordinate to any imposed end.
Hence the distinctive feature of Kant's moral theory is his enunciation of what he calls the "Categorical Imperative," the supreme inner demand of reason. The originality of his doctrine lies in his derivation of the contents of the law from the form, and to him belongs the distinction of having first most clearly formulated the principle of morality as "Duty for duty's sake."
Kant opens his Metaphysics of Morals with the words, "Nothing can possibly be conceived in the world, or even out of it, which can be called good without qualification, but a good will."
The will must be good of itself, not because of what it performs or effects. It must not depend upon the qualities of moderation, on self-control, or deliberation. For even a villain may do good actuated by such motives. Like a jewel, it must shine by its own light as a thing which has value in itself. Its usefulness or fruitfulness can neither add nor take away anything from this value. Even though a virtuous act is pleasant to the agent, or any violation of duty painful, this moral pleasure or pain cannot strictly be the motive to the act, because it follows instead of preceding the recognition of an obligation to do it.
All theories of morals are to be rejected which are based on any lower motive than the absolute disinterestedness and independence of the will. The desire for happiness, all counsels of prudence and sagacity, and every eudaemistic system which places the principle of morality outside the man himself, are inadequate as a principle of moral action. The moral law is an absolute command, a categorical imperative. But now there are three questions which we must ask with reference to this moral law. What is its source, what are its contents, and what is its value?
(1) With regard to its source—it springs directly from the reason itself. We can get no further back than that. It is a law imposed not from without, but by the very constitution of man as an intelligible being. Man as a rational being has this prerogative above all other beings, that he forms his end for himself. Nature is governed by material laws which it fulfils unconsciously. The lower animal has its ends fixed for it by its instincts. But man is distinguished by the power of knowing and realizing his own ends. The "ought" comes from within.
(2) As to its contents—it cannot contain any empirical element. It must be wholly independent of all ends or motives. The demand of the moral law has no reference to the matter of the act, but only to the form. Happiness cannot be the principle of morals. For happiness is often in conflict with our reason, and different men have very different ideas as to the nature of felicity. "If nature had desired to place our destiny in happiness it would have done better to equip us with infallible instincts rather than with the practical reason of Conscience, which is continually in conflict with our impulses." There are several kinds of imperatives. Those which demand a certain action for the sake of some result to be obtained through it are what Kant calls "hypothetical imperatives," i.e. they are subordinate to certain ends which may be good and useful, but in themselves cannot give a content to the moral law. The formula for this class of imperatives is, "Who wills the end wills the means." But the requirement of the moral command must be dictated and fulfilled solely for its own sake. It does not appeal to what a man may wish on other grounds. It holds good unconditionally and absolutely, and its formula is "Do your duty, come what will." Hypothetical Imperatives are merely maxims or counsels of prudence or skill suggesting the best means of procedure to obtain certain results. The categorical imperative, which is immediately evident so soon as the will perceives the law, and determines us to action without regard to result, alone deserves the name of a law or command. All material motives come under the principle of agreeableness or happiness, and, therefore, of self-love. The will, in so far as it follows such natural ends, is not autonomous. It makes practical reason depend on something outside of itself. All expectation of reward or punishment, the consideration of utility, and even the will of God, are rejected by Kant as imposing external constraint upon the will.
The categorical imperative being the expression of the pure Rational will is universally valid, and it may be expressed in the formula, "Act on a maxim which thou canst will to be law universal." Universality is a sign by which we can infallibly recognise the law of duty in particular cases. "If we observe the state of mind at the time of any transgression of duty, we shall find that we really do not will that our maxim should be a universal law. We only assume the liberty of making an exception in our own favour, or just for once in favour of a passing inclination."
It is thus the form and not the matter which Kant regards as the essential consideration in this law. Morality lies not in the particular things we will, but in the way in which we will them. It is a negative test at best. It does not tell us what to do, but what we must not do. It is a law of restriction, not of realization. Never act except you can generalize your action. But on this principle—that only that action is right the maxim of which can be universalized—all particular will as such is condemned, for no particular will can be universalized. There is some truth in the criticism of Jacobi, who said that Kant sets up "a will that wills nothing." In other words, you cannot carry out any particular duty absolutely and make it a universal law without making it conflict, and in the end negate some other particular duty. This maxim of Kant can accordingly only be affirmed as a law by abstracting from it all the contents of desire. Hence, like the Stoics, Kant treats desire as an intruder upon the determination of the will which must be excluded that the will may preserve its autonomy. "To be entirely free from such desires," says Kant, "must be the universal wish of every rational being." Coming into contact with the appetites or propensities of daily life, the moral law seeks to limit and restrain their operations. From this merely formal abstract principle it is impossible, without the help of other considerations, to descend to particulars. The moral law, as Kant thus expresses it, declares only the negative sine qua non of morality.
But it is only fair to say that Kant takes a more positive and concrete view. This he does by adding two new formulae for the moral law.
(3) We may, therefore, now pass from the contents or absence of contents to the worth or significance of the law. That only has inherent worth or dignity which is absolutely valuable in itself and is the condition for the sake of which all other things are valuable. This worth belongs in the highest degree to the moral law, as the expression of man's rational nature, and, therefore, the motive which stimulates a man to obey it must be nothing else but reverence for the law itself. It would be dishonoured if it were fulfilled for the sake of any external advantage. The dignity of the law, however, passes over to the man himself. Hence reverence for the worth of man is for Kant the real principle of morality. Man must perform his duty out of reverence for his own rational nature. Every rational being thus becomes a supreme end in himself. We must never regard ourselves as means, but always as ends. But every time a man follows his inclinations rather than his reason, he treats himself as a means. We must draw a distinction between persons and things. The person is inviolable, and should be respected by every other will as well as our own. Thus Kant gets a new formula for the imperative of practical reason; "always treat humanity, both in your own person and in the persons of others, as an end and never merely as a means." This formula not only compels me to preserve my own life, but also to make no deceitful promise to another. It even requires me to develop my powers and faculties, and it may even demand that I should contribute to another's happiness, or at least do nothing to hinder it. In short, I have no right to dispose of humanity in my own person or in others as I please, no right to hurt or destroy it; and, indeed, in order to realize myself as an end, I am bound to seek the ends of others, as the completion of my own ends.
Thus Kant conceives a Kingdom of Ends which includes all rational wills, as ends in themselves who treat one another as such. Each man in this way participates in the institutions of universal laws, which he obeys, because he recognises in their universality the law of his own being. Thus we are led to this final formula, "Act in conformity with the idea that the will of every rational being is a universally legislative will." This is the principle of the "autonomy of the will." For man in submitting to universal legislature is really submitting only to himself. This Kingdom of Ends, while involving a more positive view of the moral life, is still tainted with negativism. Because of the opposition between the rational will and the particular desires, the Kingdom of Ends can never be actually realized. It remains an ideal, an "ought to be." It is conceived by Kant as a kingdom of limitation rather than a kingdom of reciprocal expression and realization. Kant does not rise to the conception of an organic unity of society in and through which alone individuals can attain to their true life and expression.
The moral consciousness, as a consciousness of reason determining itself, is the guarantee of the three great truths or postulates, which metaphysics could not prove—the freedom of the will, the immortality of the soul, and the existence of God.
Kant goes on to show that the immortality of the soul is also vindicated. The law demands complete conformity with itself. But in a being, such as man is, at once sensuous and rational, this conformity can never be more than partially realized in this world. Hence the soul demands an indefinitely prolonged life to work out its ideals. There must be room for infinite progress, and continual approximation to the idea of holiness. In other words, the soul to attain to its true moral worth must be immortal. And, finally, the postulate of the idea of God is confirmed. The imperative nature of the moral law implies that there exists somewhere a good which is not only supreme but complete, an embodiment of that perfect holiness which is the source of all the conditions implied in the moral order. With the dual nature of man Kant connects in a somewhat curious way the idea of the Summum Bonum, which he defines as the union of happiness and virtue. As finite creatures endowed with sensibility we crave happiness; but as rational beings we aim at virtue. How are these opposite notions to be combined? The one is not contained in the other, nor are they causally connected. In this world they do not go together. Striving after happiness does not make a man virtuous. And he who seeks virtue does not necessarily gain happiness. Since man belongs to a sensuous world as well as to an ethical, both sides of his nature must be vindicated. There must be a sense in which felicity and holiness can be united. May it not be that in the end virtue will be seen "to be worthy of happiness," and happiness will be the crown of virtue? Faith must reach beyond the sensuous life of man to a supersensuous life, where the conflict between these two ideas does not exist, where the reality of the highest good—the Summum Bonum—will be attainable—a world in which perfect virtue will be felicity—and true felicity will be virtue. But in order to realize this ideal condition, we must not only postulate a life of infinite duration, but the existence of a Being, who is the Creator at once of the natural and the spiritual world, the cause at once of the sensuous and the rational life of man. In other words, we must believe in a God whose action is regulated with a regard to the physical and moral natures of His creatures.
It will be impossible to do more than refer to Kant's application of his principle of morals to Jurisprudence and particular Duties. As a self-conscious being and yet a particular object in the world, man's problem of life is to determine himself in relation to other subjects, who, like himself, are also particular objects. Law becomes, therefore, a corrective determination of rights and duties, and the problem of Jurisprudence is "to keep self-conscious beings in their acts from coming into collision with each other"; and such a collision is avoidable only in so far as their acts are in agreement with rules that can be universalized. The idea of right, therefore, has to do only with the external relations of one person to another. Legal right is defined by Kant as the "whole compass of the conditions under which the will of individuals is harmonized according to a universal law of freedom." He divides all rights into private and public right. To the first belong rights in things, persons, relations of contract, and of marriage. Public right is subdivided into the right of States, Nations, and of Citizens of the world.
The social contract is at once necessary and inviolable. The State protects the individual against the possibility of enslavement to others; while it limits, it also helps each to realize his freedom. The true or ideal form of State he holds to be Republican, and while he denies to the individual the right of resistance, he maintains that governments should base their authority upon justice and not on expediency.
As in his theory of Rights, so in his conception of Particular and applied Ethics, the idea of constraint or compulsion is prominent. But here it is a constraint exercised not upon others, but upon one's self. Such a compulsion of one's own desires involves an effort which is expressed in the word Virtue, or Duty. My freedom lies in my power of self-compulsion—in my ability to make myself an end in conformity with my own reason. What then are the ends which as rational beings it is our duty to set ourselves? These, Kant answers, are our own perfection and the happiness of others. One's own happiness must never be the goal of action, for what natural impulse requires cannot be duty. Nor is it my duty to further the perfection of another. That is each man's own business. We are to seek, however, the happiness of others, not, indeed, directly, but in a negative way in so far as we are to do nothing that would put a stumbling block in the way of their physical and moral well-being. Hence arises the twofold division of moral duties—duties to ourselves and duties to other men. Duties to God are excluded, for all duties are, in a sense, duties to God as the Legislator whose will is one with the moral law. (1) Duties towards one's self are treated of first negatively and then positively. The negative duties, relative to man's physical being are those which lead to self-preservation, and the maintenance of the species. The negative duties of man to himself as a moral being, are the opposite of the three vices of lying, avarice, and false humility. Under this division Kant remarks that all duties rest on his being "born judge of himself," and, therefore, the fundamental duty is expressed in the Socratic maxim, " Know thyself." The positive duties of man are simply the duties of developing his bodily and mental powers and, above all, seeking to attain to holiness. (2) Our duties to others are divided into duties which create obligation on the part of others and those which do not. The former involves the feeling of love, the latter that of respect. Love and respect as mere feelings are not duties. But the maxim of benevolence, of which well-doing is the consequence, is obligatory as a maxim of the will, being based on the moral principle of universality, which permits us to wish our own well-being only on the condition that we wish well to every other. It will thus be seen that in this doctrine of virtue there is no place for, and no justification of the natural passions as vehicles of reason. Moreover, the individual is made at once the basis and standard of all moral action. Morality is pure self-determination. The egoistic motive is the ultimate one, and the happiness of others is only to be aimed at as the condition of realizing the end of one's own being.