Can Christian practices be considered “reasonable”? This contribution raises this question with respect to the religious practice of black churches in America during the early 1960s and that of the contemporary Roman Catholic Church in Europe. The essay first explores the views of Daniel Dennett and Richard Swinburne who understand “reasonability” as “rationally justified.” It will be shown that they approach the complex phenomenon of religion as a variant of scientific or theoretical thinking. The claim of this chapter is that the question of the meaning of religious practice has to precede any epistemological research. This essay then argues, inspired by the work of Ludwig Wittgenstein, that it is better to use the concept of “credibility” rather than “rational justification” regarding the question of the reasonability of religious traditions.