open before us. For then indeed we clearly see what the Real and the Ideal (the thing in itself and the phenomenon) properly are; and this settles the principal question which has engaged the attention of philosophers since Descartes: that is to say, the question as to the relation between these two, whose complete diversity Kant had shown most thoroughly and with unexampled depth, yet whose absolute identity was immediately afterwards proclaimed by humbugs on the credit of intellectual intuition. But if we decline to avail ourselves of this insight, which is really the one strait gate to truth, we can never acquire comprehension of the intrinsic essence of Nature, to which absolutely no other road leads; for then indeed we fall into an irremovable error. Then, as I have already said, we maintain the view, that motion has two radically different primary principles with a solid partition-wall between them: _i.e._ movement by means of causes, and movement by means of the will. The first of these must then remain for ever incomprehensible as to its innermost essence, because, after all its explanations, there is still left that unknown _x_ which contains the more, the higher the object under consideration stands in the scale of beings; while the second, movement by the will, presents itself as entirely disconnected from the principle of causality; as without reason; as freedom in individual actions: in other words, as completely opposed to Nature and utterly unexplainable. On the other hand, if the above-mentioned union of our external and internal knowledge has once been accomplished at the point where both meet, we then recognise two identities in spite of all accidental differences. That is to say, we recognise the identity of causality with itself on every degree of the scale of beings, and the identity of the _x_, which at first was unknown (_i.e._ of physical forces and vital phenomena), with the will which is within us. We recognise, I say, firstly the essential identity of causality under the various forms it is forced to assume on the different degrees of the scale, as it may manifest itself, now as a mechanical, chemical, or physical cause, now as a stimulus, and again as a perceptible or an abstract motive: we know it to be one and the same, not only when a propelling body loses as much movement as it imparts by impact, but also when in the combats of thought against thought, the victorious one, as the more powerful motive, sets Man in motion, a motion which follows with no less necessity than that of the ball which is struck. Where we ourselves are the things set in motion, where therefore the kernel of the process is well and intimately known to us, instead of allowing ourselves to be dazzled and confused by this light and thereby losing sight of the causal connection as it lies before us everywhere else in the whole of Nature; instead of shutting out this insight for ever, we now apply the new