Book 1, Chapter 2: The First Societies explained simply

CHAPTER II THE FIRST SOCIETIES The most ancient of all societies, and the only one that is natural is the family: and even so the children remain attached to the father only so long as they need him for their preservation. As soon as this need ceases, the natural bond is dissolved. The children, released from the obedience they owed to the father, and the father, released from the care he owed his children, return equally to independence. If they remain united, they continue so no longer naturally, but voluntarily; and the family itself is then maintained only by convention. This common liberty results from the nature of man. His first law is to provide for his own preservation, his first cares are those which he owes to himself; and, as soon as he reaches years of discretion, he is the sole judge of the proper means of preserving himself, and consequently becomes his own master. The family then may be called the first model of political societies: the ruler corresponds to the father, and the people to the children; and all, being born free and equal, alienate their liberty only for their own advantage. The whole difference is that, in the family, the love of the father for his children repays him for the care he takes of them, while, in the State, the pleasure of commanding takes the place of the love which the chief cannot have for the peoples under him. Grotius denies that all human power is established in favour of the governed, and quotes slavery as an example. His usual method of reasoning is constantly to establish right by fact. It would be possible to employ a more logical method, but none could be more favourable to tyrants. It is then, according to Grotius, doubtful whether the human race belongs to a hundred men, or that hundred men to the human race: and, throughout his book, he seems to incline to the former alternative, which is also the view of Hobbes. On this showing, the human species is divided into so many herds of cattle, each with its ruler, who keeps guard over them for the purpose of devouring them. As a shepherd is of a nature superior to that of his flock, the shepherds of men, i.e. their rulers, are of a nature superior to that of the peoples under them. Thus, Philo tells us, the Emperor Caligula reasoned, concluding equally well either that kings were gods, or that men were beasts. The reasoning of Caligula agrees with that of Hobbes and Grotius. Aristotle, before any of them, had said that men are by no means equal naturally, but that some are born for slavery, and others for dominion. Aristotle was right; but he took the effect for the cause. Nothing can be more certain than that every man born in slavery is born for slavery. Slaves lose everything in their chains, even the desire of escaping from them: they love their servitude, as the comrades of Ulysses loved their brutish condition. If then there are slaves by nature, it is because there have been slaves against nature. Force made the first slaves, and their cowardice perpetuated the condition. I have said nothing of King Adam, or Emperor Noah, father of the three great monarchs who shared out the universe, like the children of Saturn, whom some scholars have recognised in them. I trust to getting due thanks for my moderation; for, being a direct descendant of one of these princes, perhaps of the eldest branch, how do I know that a verification of titles might not leave me the legitimate king of the human race? In any case, there can be no doubt that Adam was sovereign of the world, as Robinson Crusoe was of his island, as long as he was its only inhabitant; and this empire had the advantage that the monarch, safe on his throne, had no rebellions, wars, or conspirators to fear. "Learned inquiries into public right are often only the history of past abuses; and troubling to study them too deeply is a profitless infatuation" (_Essay on the Interests of France in Relation to its Neighbours_, by the Marquis d'Argenson). This is exactly what Grotius has done. See a short treatise of Plutarch's entitled "That Animals Reason."