Now since the form of every existing thing is that individual essence by virtue of which it is what it is and is distinguished from all other existing things, it is clear that the acquired intellect, which gives its possessor immortality, is the essence of the human being who has been privileged to acquire it: in other words, his true form, by which he is distinguished from the rest of mankind. In other men the form is the transient soul given to them at birth; but in him who has the acquired intellect even the soul itself is only a kind of matter. His essential form is “the higher knowledge,” “_the form of the soul_,” which he has won for himself by assimilating “Ideas which are separate from matter.”[99] Thus mankind is divided into two species, the difference between which is greater than that between mankind as a whole and other kinds of animals. For man is distinguished from the rest of animate nature only by having a distinctive form: in quality his form is like the forms of other living things, seeing that in his case as in theirs the individual form perishes. But the distinctive form of the man who has the acquired intellect is distinct in _quality_; for it persists for ever even after its separation from matter. Its affinity is not with the other forms in the lower world, but with those “separate forms” in the world above.[100] Thus far Maimonides followed the Arabs. But here the Arab philosophers stopped: they did not probe this idea further, did not carry it to its logical conclusions. Maimonides, on the contrary, refused to stop half-way; he did not shrink from the extremest consequences of the idea.