The principle, on which the law was established, was the _right of capture_. When any of the contending parties had overcome their opponents, and were about to destroy them, the right was considered to commence; a right, which the victors conceived themselves to have, to recall their swords, and, from the consideration of having saved the lives of the vanquished, when they could have taken them by the laws of war, to commute _blood_ for _service_. Hence the Roman lawyer, Pomponius, deduces the etymology of _slave_ in the Roman language. "They were called _servi_[044], says he, from the following circumstance. It was usual with our commanders to take them prisoners, and sell them: now this circumstance implies, that they must have been previously _preserved_, and hence the name." Such then was the _right of capture_. It was a right, which the circumstance of _taking_ the vanquished, that is, of _preserving_ them alive, gave the conquerors to their persons. By this right, as always including the idea of a previous preservation from death, the vanquished were said _to be slaves_[045]; and, "as all slaves," says Justinian, "are themselves in the power of others, and of course can have nothing of their own, so their effects followed the condition of their persons, and became the property of the captors." To examine this right, by which the vanquished were said to be slaves, we shall use the words of a celebrated Roman author, and apply them to the present case[046]. "If it is lawful," says he, "to deprive a man of his life, it is certainly not inconsistent with nature to rob him;" to rob him of his liberty. We admit the conclusion to be just, if the supposition be the same: we allow, if men have a right to commit that, which is considered as a greater crime, that they have a right, at the same instant, to commit that, which is considered as a less. But what shall we say to the _hypothesis_? We deny it to be true. The voice of nature is against it. It is not lawful to kill, but on _necessity_. Had there been a necessity, where had the wretched captive survived to be broken with chains and servitude? The very act of saving his life is an argument to prove, that no such necessity existed. The _conclusion_ is therefore false. The captors had no right to the _lives_ of the captured, and of course none to their _liberty_: they had no right to their _blood_, and of course none to their _service_. Their right therefore had no foundation in justice. It was founded on a principle, contrary to the law of nature, and of course contrary to that law, which people, under different governments, are bound to observe to one another.