Muslims do less well on the French labor market than their non Muslim counterparts. One explanation for this relative failure can be characterized by the following syllogism: (1) the empowerment of women is a sine qua non for economic progress; (2) in-group norms among Muslims do not empower women; and hence (3) Muslim communities will underperform economically relative to non-Muslim communities. This paper, relying on a unique identification strategy that isolates religion from national origin and ethnicity, and on experimental as well as survey evidence collected in France, puts this syllogism to a test. Our data show that Muslim and Christian gender norms are as postulated. However, the correlations between Muslim vs. Christian immigrants and the channels purported to link in-group gender norms to economic progress are weak and inconsistent. Speculations are offered on the intervening variables that mitigate the effect of Muslim gender norms on economic performance.