Such is the nature of the true motive of pure practical reason; it is no other than the pure moral law itself, inasmuch as it makes us conscious of the sublimity of our own supersensible existence and subjectively produces respect for their higher nature in men who are also conscious of their sensible existence and of the consequent dependence of their pathologically very susceptible nature. Now with this motive may be combined so many charms and satisfactions of life that even on this account alone the most prudent choice of a rational Epicurean reflecting on the greatest advantage of life would declare itself on the side of moral conduct, and it may even be advisable to join this prospect of a cheerful enjoyment of life with that supreme motive which is already sufficient of itself; but only as a counterpoise to the attractions which vice does not fail to exhibit on the opposite side, and not so as, even in the smallest degree, to place in this the proper moving power when duty is in question. For that would be just the same as to wish to taint the purity of the moral disposition in its source. The majesty of duty has nothing to do with enjoyment of life; it has its special law and its special tribunal, and though the two should be never so well shaken together to be given well mixed, like medicine, to the sick soul, yet they will soon separate of themselves; and if they do not, the former will not act; and although physical life might gain somewhat in force, the moral life would fade away irrecoverably. {BOOK_1|CHAPTER_3 ^paragraph 35} Critical Examination of the Analytic of Pure Practical Reason. By the critical examination of a science, or of a portion of it, which constitutes a system by itself, I understand the inquiry and proof why it must have this and no other systematic form, when we compare it with another system which is based on a similar faculty of knowledge. Now practical and speculative reason are based on the same faculty, so far as both are pure reason. Therefore the difference in their systematic form must be determined by the comparison of both, and the ground of this must be assigned.