Abstract: Discusses the view, often called Deductivism, put forward independently by the philosopher Karl Popper and the statistician and geneticist R. A. Fisher, that deductive logic suffices to tell us which is the best theory in the light of observational data. In Fisher's case, this view supported his theory of significance tests. Deductivism purports to be a radical solution of Hume's problem because, according to it, there are no specifically inductive inferences. This, and the related views of the statisticians Neyman and Pearson, are shown to be untenable.

Keywords: deductive logic, deductivism, R.A. Fisher, Neyman, Pearson, significance tests,