In the first two essays of this book, Louis Althusser analyses the work of two of the greatest thinkers of the Enlightenment ? Montesquieu and Rousseau. He shows that although they made considerable advances towards establishing a science of politics, particularly in comparison with the theorists of natural law, they nevertheless remained the victims of the ideologies of their day and class. Montesquieu accepted as given the political notions current in French absolutism; Rousseau attempted to impose by moral conversion an already outdated mode of production. The third essay examines Marx?s relationship to Hegel and elaborates on the discussions of this theme in Althusser?s earlier books, For Marx and Lenin and Philosophy. Althusser argues that Marx was able to establish a theory of historical materialism and the possibility of a Marxist philosophy of dialectical materialism not simply by turning his back on Hegel, but by extracting and converting certain categories from Hegel?s Logic and applying them to English political economy and French socialist political theory.