The Raven paradox is a paradox first presented by the German logician Carl Gustav Hempel in the 1940s. The paradox stems from two intuitive principles for inductive reasoning: (i) logically-equivalent claims are interchangeable and (ii) particular instances confirm the corresponding universal generalization. Hempel showed that (i) and (ii) together entail the unintuitive conclusion that claims of the form "All As are Bs" can be confirmed by observing non-A, non-B objects.