Thomas Hobbes (1588–1679) and Jean-Jacques Rousseau (1712–1778) were outstanding philosophers who developed the idea of a social contract. Previously, sovereigns were entitled to reign through what was known as the "divine right of kings." By the seventeenth century, however, the "divine right" was no longer sufficient or suitable. Hobbes and Rousseau thought there needed to be a "contract" between the people and their rulers.
In the absence of government, people lived in a "state of nature." Hobbes and Rousseau differed on what this really was. In his Leviathan (1651), Hobbes said our lives were “solitary, poor, nasty, brutish and short.” Men preyed incessantly on one another. Rousseau's view was more positive: he thought of the "state of nature" as something akin to the state of Indians prior to the arrival of Europeans. In other words, Hobbes thought humanity was rather evil, and Rousseau believed it were largely benevolent.
Both philosophers thought a social contract was needed, but their views on its nature was as different as their ideas on the state of nature. Hobbes believed the sovereign had one duty: to offer protection to his subjects. For Hobbes, security and safety were paramount. Rousseau believed government needed a moral character and that it was derived from the consent of the governed. Liberty and social well-being were most important to Rousseau.