If I utter the sentence: Hitler caused the outbreak of the second world war, some interested logician may translate my sentence into the words: Hitler necessitated the outbreak of the second world war, If that translation be made I do not accept it, unless the dragoman makes it clear to me that by the word “necessitate” he means nothing more than I mean by the word “cause.” In which case I can dispense with his services. But if he is embodying in his translation the thought that the outbreak of war followed from the existence of Hitler at a given moment of time, as the equality of the angles in a triangle follows from the equality of the sides (I assume that that follows), then I repudiate his translation, because I do not agree that a statement or proposition such as event x caused event y is a hypothetical proposition of the type if x then y. A fortiori it cannot be regarded by me as a reciprocal hypothetical proposition: if x then y if y then x; nor, to complete the possibilities, can I infer what I call the cause from the effect.