The Metaphysics of Morals by Immanuel Kant Chapter 1 Page 9

the happiness and satisfaction of life, or who would even reduce them below zero, is by no means morose or ungrateful to the goodness with which the world is governed, but that there lies at the root of these judgements the idea that our existence has a different and far nobler end, for which, and not for happiness, reason is properly intended, and which must, therefore, be regarded as the supreme condition to which the private ends of man must, for the most part, be postponed.

For as reason is not competent to guide the will with certainty in regard to its objects and the satisfaction of all our wants (which it to some extent even multiplies), this being an end to which an implanted instinct would have led with much greater certainty; and since, nevertheless, reason is imparted to us as a practical faculty, i.e.