Act so as to treat humanity, whether in your own person or in that of another, at all times also as an end, and not only as a means. - Immanuel Kant

A metaphysics of morals is therefore indispensably necessary, not merely because of a motive to speculation — for investigating the source of the practical basic principles that lie a priori in our reason — but also because morals themselves remain subject to all sorts of corruption as long as we are without that clue and supreme norm by which to appraise them correctly...

Everyone can see that philosophy can have her belief in a millennium, but her millennarianism is not Utopian, since the Idea can help, though only from afar, to bring the millennium to pass. The only question is: Does Nature reveal anything of a path to this end? And I say: She reveals something, but very little. This great revolution seems to require so long for its completion that the short period during which humanity has been following this course permits us to determine its path and the relation of the parts to the whole with as little certainty as we can determine, from all previous astronomical observation, the path of the sun and his host of satellites among the fixed stars. Yet, on the fundamental premise of the systematic structure of the cosmos and from the little that has been observed, we can confidently infer the reality of such a revolution. Moreover, human nature is so constituted that we cannot be indifferent to the most remote epoch our race may come to, if only we may expect it with certainty. Such indifference is even less possible for us, since it seems that our own intelligent action may hasten this happy time for our posterity. For that reason, even faint indications of approach to it are very important to us.

Morality is not the doctrine of how we may make ourselves happy, but how we may make ourselves worthy of happiness.