Critique of Judgement by Immanuel Kant Chapter 87 Page 7

The moral law as the formal rational condition of the use of our freedom obliges us by itself alone, without depending on any purpose as material condition; but it nevertheless determines for us, and indeed a priori, a final purpose towards which it obliges us to strive; and this purpose is the highest good in the world possible through freedom.

The subjective condition under which man (and, according to all our concepts, every rational finite being) can set a final purpose before himself under the above law is happiness. Consequently, the highest physical good possible in the world, to be furthered as a final purpose as far as in us lies, is happiness, under the objective condition of the harmony of man with the law of morality as worthiness to be happy.