All categories of the understanding (cause and effect, matter and form, possibility, etc.) are found to contain this movement when dissolved. And hence they have self-determination for their presupposition and explanation. It is unnecessary to add that unless one gives up trying to _imagine_ truth, that this is all very absurd reasoning. (At the end of the sixth book of Plato’s Republic, ch. xxi., and in the seventh book, ch. xiii., one may see how clearly this matter was understood two thousand, and more, years ago.) To manifest or reveal is to make known; and hence to speak of the “manifestation of a hidden and inscrutable essence” is to speak of the making known of an unknowable. Mr. Spencer goes on; no hypothesis of the universe is possible—creation not conceivable, for that would be something out of nothing—self-existence not conceivable, for that involves unlimited past time. He holds that “all knowledge is _relative_,” for all explanation is the reducing of a cognition to a more general. He says, (p. 69,) “Of necessity, therefore, explanation must eventually bring us down to the inexplicable—the deepest truth which we can get at must be unaccountable.” This much valued insight has a positive side as well as the negative one usually developed: I. (_a._) To explain something we subsume it under a more general. (_b._) The “_summum genus_” cannot be subsumed, and (_c._) Hence is inexplicable. II. But those who conclude from this that we base our knowledge ultimately upon faith (from the supposed fact than we cannot prove our premises) forget that— (_a._) If the subsuming process ends in an unknown, then all the subsuming has resulted in nothing; for to subsume something under an unknown does not explain it. (Plato’s Republic, Book VII, chap. xiii.) (_b._) The more general, however, is the more simple, and hence the “_summum genus_” is the purely simple—it is Being. But the simpler the clearer, and the pure simple is the absolutely clear. (_c._) At the “_summum genus_” subsumption becomes the principle of identity—being is being; and thus stated we have simple self-relation as the origin of all clearness and knowing whatsoever. III. Hence it is seen that it is not the mere fact of subsumption that makes something clear, but rather it is the reduction of it to identity. In pure being as the _summum genus_, the mind contemplates the pure form of knowing—“a is a,” or “a subject is a predicate”—(a is b). The pure “is” is the empty form of mental affirmation, the pure copula; and thus in the _summum genus_ the mind recognizes the pure form of itself. All objectivity is at this point dissolved into the thinking, and hence the subsumption becomes identity—(being = _ego_, or “_cogito, ergo sum_”;) the process turns round and becomes synthetic, (“dialectic” or “genetic,” as called by some). From this it is evident that self-consciousness is the basis of all knowledge.