The world is my representation: This is a truth that applies to every living and perceiving being; although only humans can bring it into reflective abstract consciousness. And if he truly does this, philosophical contemplation has entered him. It then becomes clear and certain to him that he knows no sun and no earth; but only an eye that sees a sun, a hand that feels an earth; that the world surrounding him exists only as a representation, that is, solely in relation to another, the representing one, which he himself is. If any truth can be stated a priori, it is this: for it is the assertion of that form of all possible and conceivable experience, which is more general than all others, such as time, space, and causality: for all of these already presuppose it.