A further addition to the abstract formula of the categorical imperative results from the discussion of the question, What universal ends admit of subsumption under it, i.e., stand the test of fitness to be principles of a universal legislation?  Here again Kant stands forth as an arbiter between the contending parties, and, with a firm grasp, combines the useful elements from both sides after winnowing them out from the worthless principles.  The majority of the eudemonistic systems, along with the promotion of private welfare, prescribe the furtherance of universal good without being able to indicate at what point the pursuit of personal welfare should give way to regard for the good of others, while in the perfectionist systems the social element is wanting or retreats unduly into the background.  The principle of happiness represents moral empiricism, the principle of perfection moral rationalism.  Kant resolves the antithesis by restricting the theses of the respective parties within their proper limits:  “Make thine own perfection and the happiness of others the end of thy actions;” these are the only ends which are at the same time duties.  The perfection of others is excluded by the fact that I cannot impart to anyone a good disposition, for everyone must acquire it for himself; personal happiness by the fact that everyone seeks it naturally.

This antithesis (which is crossed by the further distinction between perfect, i.e., indispensable, and imperfect duties) serves as a basis for the division of moral duties into duties toward ourselves and duties toward other men.[1] The former enjoin the preservation and development of our natural and moral powers, the latter are duties of obligation (of respect) or of merit (of love).  Since no one can obligate me to feel, we are to understand by love not the pathological love of complacency, but only the active love of benevolence or practical sympathy.  Since it is just as impossible that the increase of the evils in the world should be a duty, the enervating and useless excitation of pity, which adds to the pain of the sufferer the sympathetic pain of the spectator, is to be struck off the list of virtues, and active readiness to aid put in its place.  In friendship love and respect unite in exact equipoise.  Veracity is one of the duties toward self; lying is an abandonment of human dignity and under no conditions allowable, not even if life depends on it.

[Footnote 1:  All duties are toward men, not toward supra-human or infra-human beings.  That which we commonly term duties toward animals, likewise the so-called duties toward God, are in reality duties toward ourselves.  Cruelty to animals is immoral, because our sympathies are blunted by it.  To have religion is a duty to ourselves, because the view of moral laws as laws of God is an aid to morality.]