the necessity or the need of knowledge in general arises from the multiplicity and the separate existence of beings, thus from individuation. For suppose there only existed a single being, such a being would have no need of knowledge: because nothing would exist which was different from it, and whose existence it would therefore have to take up into itself indirectly through knowledge, i.e., image and concept. It would itself already be all in all, and therefore there would remain nothing for it to know, i.e., nothing foreign that could be apprehended as object. In the case of a multiplicity of beings, on the other hand, every individual finds itself in a condition of isolation from all the rest, and hence arises the necessity of knowledge. The nervous system, by means of which the animal individual primarily becomes conscious of itself, is bounded by a skin; yet in the brain that has attained to intellect it passes beyond this limit by means of its form of knowledge, causality, and thus there arises for it perception as a consciousness of other things, as an image of beings in space and time, which change in accordance with causality. In this sense it would be more correct to say, "Only the different is known by the different," than as Empedocles said, "Only the like is known by the like," which was a very indefinite and ambiguous proposition; although points of view may certainly also be conceived from which it is true; as, for instance, we may observe in passing that of Helvetius when he says so beautifully and happily: "Il n'y a que l'esprit qui sente l'esprit: c'est une corde qui ne frémit qu'à l'unison," which corresponds with Xenophon's "σοφον ειναι δει τον επυγνωσομενον τον σοφον" (sapientem esse opportet eum, qui sapientem agniturus sit), and is a great sorrow. But now, again, from the other side we know that multiplicity of similars only becomes possible through time and space; thus through the forms of our knowledge. Space first arises in that the knowing subject sees externally; it is the manner in which the subject comprehends something as
