We have here to do with two directions of scientific interest. The Natural-Philosophers are more or less concerned with the plenitude of the concrete phenomena of Nature, as in Geography and Ethnology. They investigate in all directions the effects of things, and think the essential nature of these is only to be discerned in such effect or working. When they do ascend beyond Nature, Soul and Spirit, to the Divine Essence, then the definition of it to which they confine themselves, or which they adopt by preference, is—‘the First Cause’, or,—‘the wise Creator’, whose goodness and wisdom appear from his works. The Logicians proceed in a very different way. The occurrence of the Particular has only a subordinate value in their eyes,—the value, merely, of an illustration of its deducibility from the Universal. While the Physicists start from effects or operations, the Logicians seek to comprehend things from principles. Everywhere they enquire after the Idea or Essence of things, up to the highest. For them,—to make the contrast more intelligible by an example—, God is not, first of all, ‘the wise Creator’, but first of all ‘the necessarily existing Being’. In the order of time the Logicians come after the Physical school, just as the Mutazilite Dialectic on its part (v. II, 3 §§ 4 and 5) brought within the scope of its consideration first God’s Working, and then his Being. We have already come to recognize Razi as the most important representative of the philosophical direction taken by the Physicists; and as for the Logical and Metaphysical efforts,—for which Kindi and others had prepared the way,—they culminate with Razi’s younger contemporary Abu Nasr ibn Mohammed ibn Tarkhan ibn Uzlag al-Farabi. 2. We cannot say much with certainty about the course of Farabi’s outward life and training. He was a quiet man, devoted to a life of philosophy and contemplation, sheltered by the powerful, and assuming at last the dress of a Sufi. His father is said to have been a Persian general, and he himself was born at Wasidj, a small fortified place in the district of Farab in Turkish Transoxiana. It was in Bagdad, and partly at the hands of a Christian preceptor Yohanna ibn Hailan, that he received his education. This embraced both literary and mathematical subjects, forming the equivalent of the ‘Trivium’ and ‘Quadrivium’ of mediæval Christendom. One or two of his writings, particularly on Music, give evidence still of his mathematical training. Legend credits him with ability to speak in all the languages of the world, seventy in number. That he understood Turkish and Persian,—an a priori probability,—is manifest from his works. Arabic he writes clearly, and with a certain grace, although now and then his fondness for synonyms and parallel clauses interferes with the precision of philosophical expression.