Carneri's examination of the primary laws of thought can be only touched upon here. In the law of Identity, or, negatively speaking, the law of Consistency,[72] there comes to our consciousness a more general Species which includes a determinate species. "The adequate, clear, correct, corresponding[73] concept is consistent with itself," means, the adequate concept finds itself again in every object which it includes. The law of Identity expresses, therefore, not entire sameness, with which the cessation of all thought would be reached, but simple consistency. It affords us, thus, the means of recognizing the Untrue in that which is not what it is called, hence also the means of recognizing the True. The law of Excluded Middle contains an extension or doubling of the law of Identity, in that the identity here appears, not in the form of consistency, but in that of contradiction; as, "either--or." Not one, but two cases are supposed, only one of which can exist or be true. The disjunctive proposition which corresponds to it is not less determinate than the categorical proposition which corresponds to the law or judgment of Identity, but is rather, on the contrary, a more forcible affirmation of it. In this determinate nature lies the worth of the Excluded Middle. Du Bois Raymond's address on the Limits of Knowledge has caused much joy to conservative thinkers; but these have made much more out of it than it really means. There is either for us a transcendental, or there is not; and if not, then we are limited to the knowledge of nature. The scientific limit set to our knowledge by our hypotheses and theories is, however, merely a limit set for the purpose of rounding knowledge to a whole, not of closing it to a further advancement; but such hypotheses must be consistent with experience and founded upon it; otherwise we leave knowledge behind us and abandon the hope of it. We cannot say what, within the province of science, man will not know, except that he never will know everything.