Let no one here offer the trivial objection that all systematic authors have ever been convinced of the truth of their systems. For this assertion is utterly false, and is grounded only in this, that few know what conviction really is. This can only be experienced by having the fullness of conviction in one’s self. Those authors were only convinced of one or the other point in their system, which perhaps was not even clearly conscious to themselves, but not of the whole of their system—they were convinced only in certain moods. This is no conviction. Conviction is that which depends on no time and no change of condition; which is not accidental to the soul, but which is the soul itself. One can be convinced only of the unchangeably and eternally True: to be convinced of error is impossible. But of such true convictions very few examples may probably exist in the history of philosophy; perhaps but one; perhaps not even this one. I do not speak of the ancients. It is even doubtful whether they ever proposed to themselves the great problem of philosophy. But let me speak of modern authors. Spinoza could not be convinced; he could only _think_, not _put faith_ in his philosophy; for it was in direct contradiction with his necessary conviction in daily life, by virtue of which he was forced to consider himself free and self-determined. He could be convinced of it only in so far as it contained truth, or as it contained a part of philosophy as a science. He was clearly convinced that mere objective reasoning would necessarily lead to his system; for in that he was correct; but it never occurred to him that in thinking he ought to reflect upon his own thinking, and in that he was wrong, and thus made his speculation contradictory to his life. Kant might have been convinced; but, if I understand him correctly, he was not convinced when he wrote his _Critique_. He speaks of _a deception, which always recurs, although we know that it is a deception_. Whence did Kant learn, as he was the first who discovered this pretended deception, that it always recurs, and in whom could he have made the experience that it did so recur? Only in himself. But to know that one deceives one’s self, and still to deceive one’s self is not the condition of conviction and harmony within—it is the symptom of a dangerous inner disharmony. My experience is that no deception recurs, for reason contains no deception. Moreover, of what deception does Kant speak? Clearly of the belief that things _per se_ exist externally and independent of us. But who entertains this belief? Not common consciousness, surely, for common consciousness only speaks _of itself_, and can therefore say nothing but that things exist for it (i. e. for us, on this standpoint of common consciousness); and that certainly is no deception, for it is our own truth. Common consciousness knows nothing of a thing _per se_, for the very reason that it is common consciousness, which surely never goes beyond itself.