According to this doctrine, ideas are empty forms of the understanding, mean nothing, and can lead to nothing; although they entertain the understanding, and offer to it an immense field for combinations, the world they present to it is purely illusory, and can serve for nothing in the real order. In contemplating these entirely empty forms, the intellect is the sport of fantastic visions, from the union of which results the spectacle which seems now to belong to reality, and now to possibility; either it is a mere nonentity, or something, and if so, it can never make us sure of the reality it possesses. 246. It is difficult to fight skepticism when it takes this ground: situated beyond the domains of reason, the decisions of reason cannot reach it. It will appeal from them all, for it begins by denying the competency of the judge. But as these skeptics admit consciousness, it is right that they should defend it against whoever attempts to deprive them of it. We believe that if the objectiveness of ideas be denied, not only all science, but also all consciousness is annihilated; and here skeptics are guilty of an inconsequence; for, while they deny the objectiveness of some ideas, they admit that of others. No consciousness, properly so called, can exist, if this objectiveness be absolutely destroyed. We beg the reader to follow us in a brief, but severe analysis of the facts of consciousness, in their relations with the objectiveness of ideas.(24) CHAPTER XXV. THE OBJECTIVE VALUE OF IDEAS. 247. The transition from subject to object, from subjective appearance to objective reality, is a problem which vexes fundamental philosophy. Consciousness will not permit us to doubt that certain things _appear_ to us in such a manner; but _are_ they in reality what they appear to us? How are we to know this? What shall assure us of this conformity of the idea with the object? The question does not relate solely to sensations; it also extends to purely intellectual ideas, even to those inundated with that internal light which we call evidence. "What I evidently see in the idea of a thing, is as I see it," philosophers have said, and all mankind with them. No one doubts what is presented to him as evidently true. But how prove that evidence is a legitimate criterion of truth?