This article defends the principle of non-establishment against 21st-century projects of political religion, constitutional theocracy and political theology. It is divided into two parts, which will appear in two consecutive issues of Philosophy & Social Criticism, 39(4–5) and 39(6). Part 1 proceeds by constructing an ideal type of political secularism, and then discussing the innovative American model of constitutional dualism regarding religion that combined constitutional protection for the freedom of religious conscience and exercise with the principle of non-establishment. The article (...) analyses the strengths and limits of the ‘separation– accommodation’ frame that became hegemonic in 1st amendment jurisprudence from the 1940s to the 1990s. It challenges the standard caricature of the American model as strictly separationist and privatizing. It then critically assesses two contemporary alternatives to that frame: the integrationist approach and the equal liberty approach. The first, disguised as a concern for pluralism and fairness, challenges ‘separation’ and political secularism in a subtle attack on the non-establishment principle, aimed at drastically narrowing its scope. Successes of this approach in recent Supreme Court jurisprudence and politics have triggered a response by liberal egalitarians. The author addresses this response – the equal liberty model – in part 2, which will appear in Philosophy & Social Criticism 39(6), arguing that although on the right track, it fails to find a middle ground between political secularism and integration. (shrink)