In Book I, Rousseau aims to discover why people gave up their natural liberty, which they possessed in the state of nature, and how political authority became legitimate. He begins with the famous sentence, "Man is born free, and everywhere he is in chains." These chains result from the obligations that each person has to the community. According to Rousseau, this sense of communal duty is founded upon convention. He denies that a legitimate, political authority can be found in the state of nature.
The oldest and only natural society is the family. However, children are only bound to their father as long they depend on him to take care of them. Once a child has reached maturity, the members of the family return to their previous state of independence. The family is the prototype for all political societies: the father is the leader, and his children are the populace. Each person gives up his liberty to receive the protection of the family and thus promote his own utility.
According to Rousseau, force cannot be the foundation for legitimate political authority. People obey those stronger than themselves out of necessity, not by choice. Thus, the right of the strongest cannot create the sense of a duty that is necessary to establishing a true right. In addition, because strength is a relative term, the effect of this right changes with the cause. As soon as one person makes himself the strongest, all previous claims established on the right of the strongest are nullified. Thus, the primary flaw with this right is that it can be broken legitimately.
Because no man has a natural authority over other men and because force cannot establish right, all legitimate authority must depend upon convention. Rousseau goes on to refute Grotius, who argues that a state can be legitimate even if the people are slaves and the government is their master. Rousseau disputes his claim that the people can alienate their liberty and give themselves to a king. According to Rousseau, no one will give up his liberty without getting something in return. A popular argument made by political philosophers holds that people can renounce their freedom in exchange for the civil tranquility offered by a monarch. Referring to contemporary situations, Rousseau asserts that this promise of civil tranquility becomes insignificant when kings drag their countries into numerous wars and place unnecessary demands on their citizens. Even if a person willingly sacrifices his own liberty, he cannot offer the freedom of his children without their consent. Thus, for such a society to be legitimate, each generation must offer their expressed approval of it.
Rousseau also refutes Grotius' idea that slavery can be considered a contract between master and servant. There is no possible compensation, Rousseau holds, for a person who has given up his freedom. Furthermore, Rousseau believes that actions can be moral only if they have been done freely. Grotius' other argument for slavery is based in war: he claims that because the victors in war have to right kill the vanquished, the latter can sell their liberty in exchange for their lives. Rousseau disputes Grotius' contention that the victors have a right to kill the vanquished. Wars are fought by states, not by men. After a nation has lost in battle, its soldiers cease being enemies to the opposing state, and no one has a right to their lives.
In Book I of The Social Contract, Rousseau sets out to determine the basis for legitimate, political authority. To complete this task, Rousseau must examine how man transitioned from the state of nature to civil society. Rousseau clearly outlines his views on the state of nature in his earlier work, Discourse on the Origin of Inequality. In Discourse, Rousseau claims that life before civil society was more peaceful, because people lived a simple existence without property or emotional attachments. Savage man thus had no sources of conflict and worried only about his own preservation. Rousseau's idea of the state of nature contradicts with that of his contemporary, Thomas Hobbes, who portrays life in the state of nature as "solitary, nasty, poor, brutish, and short." The primary difference between the two philosophers is that in Rousseau's opinion, Hobbes confuses savage man with modern man. Because Hobbes views modern man as greedy and ruthlessly ambitious, he assumes that these qualities are a part of human nature. In contrast, Rousseau believes that humans are born with a natural sense of compassion, and that the state of nature is not a "war of all against all," as Hobbes believes.
It is important to emphasize that Rousseau does not specify when the transition from the state of nature to civil society took place. He also does not give any evidence that humans behaved as he claims. In fact, Rousseau acknowledges in Discourse on the Origin of Inequality that his account may not, in fact, be an accurate depiction of the true course of events. Critics of Rousseau have focused on this lack of historical evidence to undermine his political theory, but readers should understand that Rousseau admittedly creates an ideal type in an effort to further his arguments about political authority.
In addition to Hobbes, Rousseau debates Hugo Grotius in Book I. Grotius, born in 1583, was a prominent figure in philosophy, political theory, and law during the 18th century. Grotius and Rousseau differ primarily in their ideas about rights. Grotius believes that a right is simply a power possessed by an agent, and does not require moral sanction. This contrasts sharply with Rousseau's conception of a right, which has a significant moral component. Just because the victors in war are capable of killing the vanquished, this does not give them the right to do so, according to Rousseau. Grotius also promotes the idea that rights can be transferred or sold like commodities. He uses this belief to support slavery and absolute monarchy. In contrast, Rousseau believes that rights (such as the right to freedom) are inalienable, and thus cannot be transferred under any circumstances.