towards the objective laws the attitude of the will is no longer unfailing choice, but constraint.  A constraining objective principle mentally represented, is a command; its formula is called Imperative, for which the expression is Ought.  A will perfectly good—­i.e., subjectively determined to follow the objective laws of good as soon as conceived—­knows no Ought.  Imperatives are only for an imperfect, such as is the human, will. Hypothetical Imperatives represent the practical necessity of an action as a means to an end, being problematical or assertory principles, according as the end is possible or real. Categorical Imperatives represent an action as objectively necessary for itself, and count as apodeictical principles.

To the endless number of possible aims of human action correspond as many Imperatives, directing merely how they are to be attained, without any question of their value; these are Imperatives of Fitness.  To one real aim, existing necessarily for all rational beings, viz., Happiness, corresponds the Imperative of Prudence (in the narrow sense), being assertory while hypothetical.  The categorical Imperative, enjoining a mode of action for itself, and concerned about the form and principle of it, not its nature and result, is the Imperative of Morality.  These various kinds of Imperatives, as influencing the will, may be distinguished as Rules (of fitness), Counsels (of prudence), Commands or Laws (of morality); also as technical, pragmatical, moral.

Now, as to the question of the possibility of these different Imperatives—­how they can be supposed able to influence or act upon the Will—­there is in the first case no difficulty; in wishing an end it is necessarily implied that we wish the indispensable means, when this is in our power.  In like manner, the Imperatives of Prudence are also analytical in character (i.e., given by implication), if only it were possible to have a definite idea of the end sought, viz., happiness.  But, in fact, with the elements of happiness to be got from experience at the same time that the idea requires an absolute whole, or maximum, of satisfaction now and at every future moment, no finite being can know precisely what he wants, or what may be the effect of any of his wishes.  Action, on fixed principles, with a view to happiness, is, therefore, not possible; and one can only follow empirical directions, about Diet, Frugality, Politeness, &c., seen on the whole to promote it.  Although, however, there is no certainty of causing happiness, and the Imperatives with reference thereto are mere counsels, they retain their character of analytical propositions, and their action on the will is not less possible than in the former case.