Karl Popper's falsifiability (1902-1994) defines at the same time the standard of scientific knowledge, and is presented in the form of a criterion of the empirical character of any scientific theory. The thesis reflects the ambiguity of an epistemology that is grounded in potential logic while aiming practical effectivity. It is impossible with such a criterion to rule on the scientificity of disciplines as diverse as Marxism, psychoanalysis, the theory of the evolution, astrology, studied by Popper and excluded from the field of sciences for lack of predictability. The thesis also highlights that, although very influential in biology, Popper’s normative epistemology has never really been applied, even by his followers like Jacques Monod, and is not applicable. The reasons for these failures must be investigated not only in potential logic, but also in the deductive-nomological model, the basis of the criterion, and which will become the norm in empirical science. If D-N model of explanation, formalized later by Carl Hempel, can be used for the construction of the modus operandi of the falsification in physics, it cannot be applied in the disciplines where the existence of laws remains problematic and where the concept of prediction is plural, live in biology. Finally the thesis, based on a critical analysis of Popper’s epistemology, proposes a typology of predictions, specifies biological statements and tries to look at another criterion of scientificity that takes greater account of science in action.
