 The idea of the social contract goes back at least to Protagoras and Epicurus. In its recognizably modern form, however, the idea is revived by Thomas Hobbes and was later developed, in different ways, by John Locke, Jean-Jacques Rousseau, and Immanuel Kant. After Kant, the idea fell out of favor with political philosophers until it was resurrected by John Rawls. It is now at the heart of the work of a number of moral and political philosophers.