Hempel's Raven(ヘンペルのカラスHenperu no Karasu), based on the raven paradox, was proposed to illustrate a contradiction between inductive and deductive logic. Premise: All ravens are black.Material Implication: Anything non-black is not a raven. Lacking a raven to observe, the entire observable set of non-ravens can be taken as evidence of the raven's blackness. Even its most accepting critics are doubtful of the qualify of proof that can be derived from this, but it can be used to further undermine already weak arguments.