  Transcendental arguments are controversial. One controversy surrounds the precise content of their conclusions and what exactly is presupposed. Should one conclude that the world must be a certain way or merely that we have to think that it is a certain way, in order to have the experience and thoughts at issue? The modern debate finds its counterpart in debate among scholars about what Aristotle is aiming to do in his elenctic discussion. There are two main possibilities. Aristotle may be aiming to show that the ontological version of the principle of non-contradiction is true, or he may be aiming to show merely that it cannot be disbelieved.