The history of philosophy, according to Hegel, is not a collection of opinions but the effort that humankind makes to understand their own existence. The aim of this paper is to understand the history of philosophy according to four thinkers: Montesquieu, Rousseau, Kant and Hegel. Law was chosen as a common point among these philosophers. Hegel was taken as the landmark to analize the others, whose approaches of the concept of law are taken as parameters. For Hegel, the law represents a necessary historical determination that enhances freedom. Hegel recovers Montesquieu's, Rousseau's and Kant's conception of law, signaling their individual contribution and their limitations. Hegel's conclusion is that his predecessors confirm that law is the central feature of life in a modern, free society. [ABSTRACT FROM AUTHOR]