This paper is a survey of Father Mersenne’s views about the classification of sciences, its reasons and its practical consequences. Some emphasis is put on the interconnection between Mersenne’s two majors ideas about the practice of science : scientific research is an activity mostly devoted to religious apology and to the edification of the people. This religious concern allows him to resist two of the most influential philosophical streams of his time, scepticism and alchemy, which provide some favorite opponents to (...) his works. We also show how an analogical kinship based on theological considerations and on the classification of sciences gives ground to the same kind of arguments shaping his views about arithmetic, language, and music. Finally, we focus on the connection between Mersenne’s theses, especially about the nature and virtue of language and sound, and a more general discussion of the scientific status of music and language in the context of the blooming of academies. (shrink)