The great men, who in France prepared men's minds for the coming revolution, were themselves extreme revolutionists. They recognized no external authority of any kind whatever. Religion, natural science, society, political institutions, everything, was subjected to the most unsparing criticism; everything must justify its existence before the judgment-seat of reason, or give up existence. Reason became the sole measure of everything. It was the time when, as Hegel says, the world stood upon its head;[1] first, in the sense that the human head, and the principles arrived at by its thought, claimed to be the basis of all human action and association; but by and by, also, in the wider sense that the reality which was in contradiction to these principles had, in fact, to be turned upside down. Every form of society and government then existing, every old traditional notion was flung into the lumber-room as irrational: the world had hitherto allowed itself to be led solely by prejudices; everything in the past deserved only pity and contempt. Now, for the first time, appeared the light of day, the kingdom of reason; henceforth superstition, injustice, privilege, oppression, were to be superseded by eternal truth, eternal Right, equality based on Nature and the inalienable rights of man. We know to-day that this kingdom of reason was nothing more than the idealized kingdom of the bourgeoisie; that this eternal Right found its realization in bourgeois justice; that this equality reduced itself to bourgeois equality before the law; that bourgeois property was proclaimed as one of the essential rights of man; and that the government of reason, the Contrat Social of Rousseau, came into being, and only could come into being, as a democratic bourgeois republic. The great thinkers of the eighteenth century could, no more than their predecessors, go beyond the limits imposed upon them by their epoch.