The 18th century German jurist Johann Gottlieb Heineccius (1681–1741) argues that because all “men” are by nature equal we should treat others as equally human and refrain from causing them any injury to the things they have have by nature or have acquired justly:
SECTION CLXXVII. First of all, it ought to be laid down as a maxim, that men are by nature equal, being composed of the same essential parts; and because tho’ one man may share perfections, as it were by his good lot, above others, yet different degrees of perfection do not alter the essence of man, but all men are equally men: whence it follows, that every one ought to treat every other as equally a man with himself, and not to arrogate to himself any privilege in things belonging to many by perfect right, without a just cause; and therefore not to do to any other what he would not have done to himself.
SECTION CLXXVIII. Since therefore we ought not to do to any one what we would not have done to ourselves; but none of us would like to be deprived by any other of our perfection and happiness which we have by nature, or have justly acquired; i.e. to be injured or hurt…
About this Quotation:
Heineccius was an important transitional figure between the 17th century natural law theorists like Grotius and those of the late Enlightenment like Immanuel Kant. What is striking in this passage is the Kantian notion that we must treat others as an end in themselves and not as some means (or tool) which we can use to further our own selfish ends. Although “men” were obviously not equal in some physical sense they were all equally “men” in that they had rights which should respected by others, the most important of which was the right to life. Heineccius is most particular that since “the perfection and happiness of man consists in life” and is the foundation upon which all other rights are based, anything which tends to injure this right, such as theft, violence, or death, must be avoided. To do otherwise would be to deprive us of “our perfection and happiness which we have by nature, or have justly acquired.” His conclusion is that “it is self-evident, that it is our duty not to kill any person; not to do the least detriment to his health; not to give any occasion to his sickness, pain, or death, or not to expose him to any danger, without having a right to do it.” And the right to do THIS is very strictly limited in Heineccius' view.