When it is said of the perfection that belongs to man generally (properly speaking to humanity) that it is in itself a duty to make this our end it must be placed in that which may be the effect of one's deed not in that which is merely an endowment for which we have to thank nature; for otherwise it would not be duty. Consequently it can be nothing else than the cultivation of one's power (or natural capacity) and also of one's will (moral disposition) to satisfy the requirement of duty in general.