This paper demonstrates how ideology plays a major, but previously neglected role in Rousseau's treatment of politics in the Social Contract. Specifically, it shows how a number of key elements in his line of argument come close to ideology criticism as it is conceived in Louis Althusser's theory of ideological state apparatuses. This is the case not just in relation to the distinction between general will and particular will, but also in relation to such concepts as property and social contract. (...) However, the paper also demonstrates how this pre-Marxist understanding of ideology co-exists in the text with a different and more primitive understanding of ideology which is incompatible with Marxism and which points back to Rousseau's previous discourse on the origins of inequality. The paper concludes that while there are definitely elements in Rousseau's text which point toward a future development of the theme of ideology in Marxist theory, the Social Contract on the whole is characterized by heterogeneity on this topic. (shrink)