Book I, Chapter IV
Since no man has a natural authority over his fellow, and force creates no right, we must conclude that conventions form the basis of all legitimate authority among men.
If an individual, says Grotius, can alienate his liberty and make himself the slave of a master, why could not a whole people do the same and make itself subject to a king? There are in this passage plenty of ambiguous words which would need explaining; but let us confine ourselves to the word alienate. To alienate is to give or to sell. Now, a man who becomes the slave of another does not give himself; he sells himself, at the least for his subsistence: but for what does a people sell itself? A king is so far from furnishing his subjects with their subsistence that he gets his own only from them; and, according to Rabelais, kings do not live on nothing. Do subjects then give their persons on condition that the king takes their goods also? I fail to see what they have left to preserve.
It will be said that the despot assures his subjects civil tranquillity. Granted; but what do they gain, if the wars his ambition brings down upon them, his insatiable avidity, and the vexatious conduct of his ministers press harder on them than their own dissensions would have done? What do they gain, if the very tranquillity they enjoy is one of their miseries? Tranquillity is found also in dungeons; but is that enough to make them desirable places to live in? The Greeks imprisoned in the cave of the Cyclops lived there very tranquilly, while they were awaiting their turn to be devoured.
To say that a man gives himself gratuitously, is to say what is absurd and inconceivable; such an act is null and illegitimate, from the mere fact that he who does it is out of his mind. To say the same of a whole people is to suppose a people of madmen; and madness creates no right.
Even if each man could alienate himself, he could not alienate his children: they are born men and free; their liberty belongs to them, and no one but they has the right to dispose of it. Before they come to years of discretion, the father can, in their name, lay down conditions for their preservation and well-being, but he cannot give them, irrevocably and without conditions: such a gift is contrary to the ends of nature, and exceeds the rights of paternity. It would therefore be necessary, in order to legitimise an arbitrary government, that in every generation the people should be in a position to accept or reject it; but, were this so, the government would be no longer arbitrary.
To renounce liberty is to renounce being a man, to surrender the rights of humanity and even its duties. For him who renounces everything no indemnity is possible. Such a renunciation is incompatible with man's nature; to remove all liberty from his will is to remove all morality from his acts. Finally, it is an empty and contradictory convention that sets up, on the one side, absolute authority, and, on the other, unlimited obedience. Is it not clear that we can be under no obligation to a person from whom we have the right to exact everything? Does not this condition alone, in the absence of equivalence or exchange, in itself involve the nullity of the act? For what right can my slave have against me, when all that he has belongs to me, and, his right being mine, this right of mine against myself is a phrase devoid of meaning?
Grotius and the rest find in war another origin for the so-called right of slavery. The victor having, as they hold, the right of killing the vanquished, the latter can buy back his life at the price of his liberty; and this convention is the more legitimate because it is to the advantage of both parties.
But it is clear that this supposed right to kill the conquered is by no means deducible from the state of war. Men, from the mere fact that, while they are living in their primitive independence, they have no mutual relations stable enough to constitute either the state of peace or the state of war, cannot be naturally enemies. War is constituted by a relation between things, and not between persons; and, as the state of war cannot arise out of simple personal relations, but only out of real relations, private war, or war of man with man, can exist neither in the state of nature, where there is no constant property, nor in the social state, where everything is under the authority of the laws.
Individual combats, duels and encounters, are acts which cannot constitute a state; while the private wars, authorised by the Establishments of Louis IX, King of France, and suspended by the Peace of God, are abuses of feudalism, in itself an absurd system if ever there was one, and contrary to the principles of natural right and to all good polity.
War then is a relation, not between man and man, but between State and State, and individuals are enemies only accidentally, not as men, nor even as citizens,  but as soldiers; not as members of their country, but as its defenders. Finally, each State can have for enemies only other States, and not men; for between things disparate in nature there can be no real relation.
Furthermore, this principle is in conformity with the established rules of all times and the constant practice of all civilised peoples. Declarations of war are intimations less to powers than to their subjects. The foreigner, whether king, individual, or people, who robs, kills or detains the subjects, without declaring war on the prince, is not an enemy, but a brigand. Even in real war, a just prince, while laying hands, in the enemy's country, on all that belongs to the public, respects the lives and goods of individuals: he respects rights on which his own are founded. 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 and meaningless. The words slave and right contradict each other, and are mutually exclusive. It will always be equally foolish for a man to say to a man or to a people: "I make with you a convention wholly at your expense and wholly to my advantage; I shall keep it as long as I like, and you will keep it as long as I like."
 The Romans, who understood and respected the right of war more than any other nation on earth, carried their scruples on this head so far that a citizen was not allowed to serve as a volunteer without engaging himself expressly against the enemy, and against such and such an enemy by name. A legion in which the younger Cato was seeing his first service under Popilius having been reconstructed, the elder Cato wrote to Popilius that, if he wished his son to continue serving under him, he must administer to him a new military oath, because, the first having been annulled, he was no longer able to bear arms against the enemy. The same Cato wrote to his son telling him to take great care not to go into battle before taking this new oath. I know that the siege of Clusium and other isolated events can be quoted against me; but I am citing laws and customs. The Romans are the people that least often transgressed its laws; and no other people has had such good ones.