A man shouldn’t claim to know even himself as he really is by knowing himself through inner sensation — i.e. by introspection. For since he doesn’t p… - Immanuel Kant

A man abandoned by himself on a desert island would adorn neither his hut nor his person; nor would he seek for flowers, still less would he plant them, in order to adorn himself therewith. It is only in society that it occurs to him to be not merely a man, but a refined man after his kind (the beginning of civilization). For such do we judge him to be who is both inclined and apt to communicate his pleasure to others, and who is not contented with an object if he cannot feel satisfaction in it in common with others. Again, every one expects and requires from every one else this reference to universal communication of pleasure, as it were from an original compact dictated by humanity itself.

War itself requires no particular motivation, but appears to be ingrained in human nature and is even valued as something noble; indeed, the desire for glory inspires men to it, even independently of selfish motives.

"On the other hand, the moral law, although it gives no such prospect, does provide a fact absolutely inexplicable from any data of the world of sense or from the whole compass of the theoretical use of reason, and this fact points to a pure intelligible world — indeed, it defines it positively and enable us to know something of it, namely a law.

This law gives to the sensible world, as sensuous nature (as this concerns rational beings), the form of an intelligible world, i.e., the form of supersensuous nature, without interfering with the mechanism of the former. Nature, in the widest sense of the word, is the existence of things under laws. The sensuous nature of rational beings in general is their existence under empirically conditioned laws, and therefore it is, from the point of view of reason, heteronomy. The supersensuous nature of the same beings, on the other hand, is their existence according to laws which are independent of all empirical conditions and which therefore belong to the autonomy of pure reason. And since the laws, according to which the existence of things depends on cognition, are practical, supersensuous nature, so far as we can form a concept of it, is nothing else than nature under the autonomy of the pure practical reason. The law of this autonomy is the moral law, and it, therefore, is the fundamental law of supersensuous nature and of a pure world of the understanding, whose counterpart must exist in the world of sense without interfering with the laws of the latter. The former could be called the archetypal world (*natura archetypa*) which we know only by reason; the latter, on the other hand, could be called the ectypal world (*natura ectypa*), because it contains the possible effect of the idea of the former as the determining ground of the will." — from_Critique of Practical Reason_. Translated, with an Introduction by Lewis White Beck, p. 44.