The cogito teaches us that the existence of consciousness is indistinguishable from the consciousness of existing, and that therefore there can be nothing in it of which it is unaware, and that conversely, everything that it knows with certainty it finds in itself; that consequently the truth or falsity of an experience must not reside in its relation to an external reality, but be capable of being read off from it as intrinsic denominations, without which they could never be recognized.