In his seminal paper “Two Liberal Traditions”, Larry Siedentop argues that one of the main traits that sets the French liberal tradition apart from its mainstream Anglo-American equivalent is its original understanding of the concept of liberty. French liberals, he argues, did not restrict modern liberty to non-interference or the absence of impediment, but always insisted on the importance of political liberty as a complement to civil liberty. French liberals, he adds, praised political participation because of the moralizing impact it could have on citizens. I contend that this distinctive trait acquires a particular significance when one looks at how each tradition has defined the role religion could play in modern liberal societies. In Anglo-American liberalism, state neutrality has been envisaged as a way to bolster the moral autonomy of individuals in religious matters. As a beneficial way of accommodating religious differences, state neutrality sanctifies non-interference in the cultivation of personal beliefs. The latter, however, are considered to be a private matter that is ultimately politically irrelevant. But for figures like Constant or Tocqueville, state neutrality was always conceived as a precondition for the promotion of a liberal form of religiosity, which was seen as an indispensable support for political liberty. They endowed religion with a positive, moralizing role, namely to encourage citizens to engage in political action. Drawing attention to these different treatments of religion in the two liberal traditions allows us to perceive, I conclude, how the standard correlation between liberalism and indifference to religion originates to a great extent in the mainstream Anglo-American tradition, and neglects French liberalism. For Constant and Tocqueville, state neutrality in religious matters did not imply that liberalism as a political theory had to be impervious to religion. Quite the contrary: French liberalism, because it relied on religion for the preservation of liberty, was conceived as a political project with deeply religious ramifications.