Age of Enlightenment
John Locke, one of the most influential Enlightenment thinkers, based his governance philosophy in social contract theory, a subject that permeated Enlightenment political thought. The English philosopher Thomas Hobbes ushered in this new debate with his work Leviathan in 1651. Hobbes also developed some of the fundamentals of European liberal thought: the right of the individual; the natural equality of all men; the artificial character of the political order (which led to the later distinction between civil society and the state); the view that all legitimate political power must be "representative" and based on the consent of the people; and a liberal interpretation of law which leaves people free to do whatever the law does not explicitly forbid.

Q: Thomas Hobbes ushered in the new debate of social contract theory through which work of his?
Leviathan