482.
Where our ignorance really begins, at that point from which we can see no further, we set a word; for instance, the word "I," the word "do," the word "suffer"—these concepts may be the horizon lines of our knowledge, but they are not "truths."
483.
Owing to the phenomenon "thought," the ego is taken for granted; but up to the present everybody believed, like the people, that there was something unconditionally certain in the notion "I think," and that by analogy with our understanding of all other causal reactions this "I" was the given cause of the thinking. However customary and indispensable this fiction may have become now, this fact proves nothing against the imaginary nature of its origin; it might be a life-preserving belief and still be false.
484.
"Something is thought, therefore there is something that thinks": this is what Descartes' argument amounts to. But this is tantamount to considering our belief in the notion "substance" as an "a priori" truth:—that there must be something "that thinks" when we think, is merely a formulation of a grammatical custom which sets an agent to every action. In short, a metaphysico-logical postulate is already put forward here—and it is not merely an ascertainment of fact.... On Descartes' lines nothing absolutely certain is attained, but only the fact of a very powerful faith.
If the proposition be reduced to "Something is thought, therefore there are thoughts," the result is mere tautology; and precisely the one factor which is in question, the "reality of thought," is not touched upon,—so that, in this form, the apparitional character of thought cannot be denied. What Descartes wanted to prove was, that thought not only had apparent reality, but absolute reality.
485.
The concept substance is an outcome of the concept subject, and not conversely! If we surrender the concept soul, the subject, the very conditions for the concept "substance" are lacking. Degrees of Being are obtained, but Being is lost.