This chapter deals with the way that religious conversions have to be professed and presented in the secular age. The first section tries to examine the concept of 'grammar' and its possible application to conversions. The second part presents the relationship between converts and their new churches, seen as institutions. The third part deals with the work of converts with regards to their relatives and the conditions of reception of their conversion. Conversion is seen as an interaction process between an avowal and the recognition of this avowal by others. The last part envisages the secular age (and its specific French form, the concept of laïcité) as a frame for becoming a believer in an unbelieving word. The conclusion tries to shed some light on two underrated forms of conversion: fanaticism and mysticism. Introduction: