Strict definition edit According to Michel Blay[8], science is “the clear and certain knowledge of something, based either on obvious principles and demonstrations, or on experimental reasoning, or even on the analysis of societies and human facts ". This definition makes it possible to distinguish the three types of science: the exact sciences, including mathematics and “mathematized sciences” such as theoretical physics; physicochemical and experimental sciences (natural and material sciences, biology, medicine); the human sciences, which concern the human being, his history, his behavior, language, the social, the psychological, the political.