According to Kant, it is as much the province of the practical reason to lay down laws for action as it is the province of pure reason to determine the conditions of thought, though the practical reason can define only the form of action which shall be in the spirit of duty.  It cannot present duty to us as an object of desire.  Desire can be only a form of self-love.  In the end it reckons with the advantage of having done one’s duty.  It thus becomes selfish and degraded.  The identification of duty and interest was particularly offensive to Kant.  He was at war with every form of hedonism.  To do one’s duty because one expects to reap advantage is not to have done one’s duty.  The doing of duty in this spirit simply resolves itself into a subtler and more pervasive form of selfishness.  He castigates the popular presentation of religion as fostering this same fault.  On the other hand, there is a trait of rigorism in Kant, a survival of the ancient dualism, which was not altogether consistent with the implications of his own philosophy.  This philosophy afforded, as we have seen, the basis for a monistic view of the universe.  But to his mind the natural inclinations of man are opposed to good conscience and sound reason.  He had contempt for the shallow optimism of his time, according to which the nature of man was all good, and needed only to be allowed to run its natural course to produce highest ethical results.  He does not seem to have penetrated to the root of Rousseau’s fallacy, the double sense in which he constantly used the words ‘nature’ and ‘natural.’  Otherwise, Kant would have been able to repudiate the preposterous doctrine of Rousseau, without himself falling back upon the doctrine of the radical evil of human nature.  In this doctrine he is practically at one with the popular teaching of his own pietistic background, and with Calvinism as it prevailed with many of the religiously-minded of his day.  In its extreme statements the latter reminds one of the pagan and oriental dualisms which so long ran parallel to the development of Christian thought and so profoundly influenced it.

Kant’s system is not at one with itself at this point.  According to him the natural inclinations of men are such as to produce a never-ending struggle between duty and desire.  To desire to do a thing made him suspicious that he was not actuated by the pure spirit of duty in doing it.  The sense in which man may be in his nature both a child of God, and, at the same time, part of the great complex of nature, was not yet clear either to Kant or to his opponents.  His pessimism was a reflection of his moral seriousness.  Yet it failed to reckon with that which is yet a glorious fact.  One of the chief results of doing one’s duty is the gradual escape from the desire to do the contrary.  It is the gradual fostering by us, the ultimate dominance in us, of the desire to do that duty.  Even to have seen one’s duty is the dawning in us of this high desire.  In the lowest man there is