The object of the war being the destruction of the hostile State, the other side has a right to kill its defenders, while they are bearing arms; but as soon as they lay them down and surrender, they cease to be enemies or instruments of the enemy, and become once more merely men, whose life no one has any right to take. Sometimes it is possible to kill the State without killing a single one of its members; and war gives no right which is not necessary to the gaining of its object. These principles are not those of Grotius: they are not based on the authority of poets, but derived from the nature of reality and based on reason.
The right of conquest has no foundation other than the right of the strongest. If war does not give the conqueror the right to massacre the conquered peoples, the right to enslave them cannot be based upon a right which does not exist. No one has a right to kill an enemy except when he cannot make him a slave, and the right to enslave him cannot therefore be derived from the right to kill him. It is accordingly an unfair exchange to make him buy at the price of his liberty his life, over which the victor holds no right. Is it not clear that there is a vicious circle in founding the right of life and death on the right of slavery, and the right of slavery on the right of life and death?
Even if we assume this terrible right to kill everybody, I maintain that a slave made in war, or a conquered people, is under no obligation to a master, except to obey him as far as he is compelled to do so. By taking an equivalent for his life, the victor has not done him a favour; instead of killing him without profit, he has killed him usefully. So far then is he from acquiring over him any authority in addition to that of force, that the state of war continues to subsist between them: their mutual relation is the effect of it, and the usage of the right of war does not imply a treaty of peace. A convention has indeed been made; but this convention, so far from destroying the state of war, presupposes its continuance.
So, from whatever aspect we regard the question, the right of slavery is null and void, not only as being illegitimate, but also because it is absurd