Abstract

According to Nicod's criterion of confirmation, a hypothesis of the form ‘All P are Q’ is confirmed by its positive instances, i.e. by entities that are P and Q. It is well known, however, that the criterion gives origin to counterintuitive results. For example, it sanctions the confirmation of ‘All nonblacks are nonravens’ by a nonblack nonraven. Since this hypothesis is logically equivalent to ‘All ravens are black,’ it follows that the criterion indirectly sanctions the counterintuitive confirmation of ‘All ravens are black’ by a non black nonraven, e.g. by a white shoe.