Only by what a man does heedless of enjoyment, in complete freedom and independently of what he can produce passively from the hand of nature, does h… - Immanuel Kant

To be is to do.

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.

I maintain that in every special natural doctrine only so much science proper is to be met with as mathematics; for... science proper, especially of nature, requires a pure portion, lying at the foundation of the empirical, and based upon à priori knowledge of natural things. ...the conception should be constructed. But the cognition of the reason through construction of conceptions is mathematical. A pure philosophy of nature in general, namely, one that only investigates what constitutes a nature in general, may thus be possible without mathematics; but a pure doctrine of nature respecting determinate natural things (corporeal doctrine and mental doctrine), is only possible by means of mathematics; and as in every natural doctrine only so much science proper is to be met with therein as there is cognition à priori, a doctrine of nature can only contain so much science proper as there is in it of applied mathematics.