 Deductive or a priori reasoning, Mill thinks, is similarly empty. Predating the revolution in logic that the late nineteenth-century ushered in, Mill thinks of deductive reasoning primarily in terms of the syllogism. Syllogistic reasoning, he argues can elicit no new truths about how the world is: “nothing ever was, or can be proved by syllogism which was not known, or assumed to be known, before” (System, VII: 183).