§ 52b. The falsehood of mere Ideas, which cannot be experienced, cannot be discovered by reference to experience. The hidden dialectic of the four natural Ideas of pure reason, however, reveals their false dogmatism. Reason's assertions are based on universally admitted principles while contrary assertions are deduced from other universally acknowledged principles. Contradictory assertions are both false when they are based on a self–contradictory concept. There is no middle between the two false contradictory assertions and therefore nothing is thought by the self–contradictory concept on which they are based.