A criterion offered by French philosopher Jean Nicod (1893-1924) for when one proposition confirms another.
A hypothesis of the form ‘All A are B’ is confirmed by objects that are A and B, and discontinued by objects that are A and not B, objects that are not A being irrelevant.
An advantage of this last clause is that it avoids certain paradoxes raised by Carl Gustav Hempel(1905-1997); but a disadvantage (apart from its being limited in scope) is that a hypothesis will need different evidence to confirm or disconfirm it, according to the terms in which it is formulated.
C G Hempel, ‘Studies in the Logic of Confirmation’, Mind (1945); reprinted with additions in C G Hempel Aspects of Scientific Explanation (1965)
A condition governing the confirmation of a general hypothesis by particular pieces of evidence, proposed by the French philosopher Jean Nicod (1893–1924) in his Foundations of Geometry and Induction (1930). It requires that an instance of a generalization that all As are B provides a positive, confirming piece of evidence for the generalization; evidence of something that is neither A nor B is irrelevant to it, as is evidence of something that is B but not A. The principle is put under pressure by Hempel’s paradox, which apparently yields circumstances in which something that is neither A nor B may confirm the generalization.