That this doctrine is at direct variance with the universal convictions of mankind, is too evident to require the slightest proof. That it is _unphilosophical_, as well as _unpopular_, may be made apparent by two very simple considerations. The _first_ is, that it assumes without proof the only point in question, namely, that the objects of our knowledge are nothing but the ideas of our own minds; whereas it is affirmed, on the other side, and surely with at least an equal amount of apparent reason, that we are so constituted as to have a direct perception of external objects as well as of internal mental states. The _second_ is, that the very formula of Idealism, which represents the "Non-ego" as a mere modification of the conscious "Ego," seems to involve a palpable contradiction; since it recognizes, in a certain sense, _the difference between the "Ego and the Non-ego,"_ and yet, in the same breath, annihilates that difference, and proclaims their "identity."[138] Fichte admits, indeed, that we have the idea of something which is _not-self_; but instead of ascribing it to an external object, he accounts for it by a law of our mental nature, which constrains us to _create a limit_, so as to give a determinate character to our thought. The three technical formulas, therefore, which are said[139] to express, respectively,--the affirmation of self,--the affirmation of not-self,--and the determination of the one by the other,--are all equally the products of our own mental laws, and do not necessarily require the supposition of any external object; and hence it follows that Self is the one only absolute principle, and that everything else that is conceived of is constructed out of purely subjective materials. The question whether the "object" be the generative principle of the "idea," or _vice versa_, is thus superseded; for there is no longer any distinction between "object" and "subject;" existence is identified with thought; the _Ego_ and the _Non-ego_ unite in one absolute existence; and Self becomes the sole Subject-object, the percipient and the perceived, the knowing and the known. Of course, on this theory, there is no knowledge of God, just as there can be no knowledge of Nature, and no knowledge of our fellow-men, as distinct objective realities; it is a system of pure Idealism, which, if consistently followed out, must terminate in utter _skepticism_ in regard to many of the most familiar objects of human knowledge; or, rather, in the hands of a thoroughly consequent reasoner, it must issue, as Jacobi endeavored to show, in absolute _Nihilism_; since we can have no better reason for believing in the existence of Self than we have for believing in the reality of an external world, and the coexistence of our fellow-men. Each of these beliefs is equally the spontaneous product of certain mental laws, which are just as trustworthy, and need as little to be proved, in the one case as in the other.