since no one undertakes an obligation without a motive, which means, in this case, without seeing some advantage for himself. There is only =one= obligation that I know of which is not subject to an agreement, but arises directly and solely through an act; this is because one of the persons with whom it has to do was not in existence when it was contracted. I refer to the duty of parents towards their children. Whoever brings a child into the world, has incumbent on him the duty of supporting his offspring, until the latter is able to maintain himself; and should this time never come, owing to incapacity from blindness, deformity, cretinism, and the like, neither does the duty ever come to an end. It is clear that merely by failing to provide for the needs of his son, that is, by a simple omission, the father would injure him, indeed jeopardise his life. Children's duty towards their parents is not so direct and imperative. It rests on the fact that, as every duty involves a right, parents also must have some just claim on their issue. This is the foundation of the duty of filial obedience, which, however, in course of time ceases simultaneously with the right out of which it sprang. It is replaced by gratitude for that which was done by father and mother over and above their strict duty. Nevertheless, although ingratitude is a hateful, often indeed a revolting vice, gratitude cannot be called a =duty=; because its omission inflicts no injury on the other side, and is therefore no =wrong=. Otherwise we should have to suppose that in his heart of hearts the benefactor aims at making a good bargain. It should be noticed that reparation made for harm done may also be regarded as a duty arising directly through an action. This, however, is something purely negative, as it is nothing but an attempt to remove and blot out the consequences of an unjust deed, as a thing that ought never to have taken place. Be it also observed that equity[8] is the foe of justice, and often comes into harsh collision with it; so that the former ought only to be admitted within certain limits. The German is a friend of equity, while the Englishman holds to justice.