views of those commentators, and endeavoured to defend the orthodoxy of Aristotle by making them responsible for apparent discrepancies with the teaching of revelation. He was interested also in the occult sciences, as appears from his treatises “On geomancy,” “On the Jinn,” and “On dreams.” His chemical treatise called _kimiya t-Tabish_, “the chemistry of things heated,” has been classed as a work on natural science and also as a treatise on magic; this was the unfortunate direction which Arabic chemistry was taking. He also wrote several works on music. (Cf. Schmölders: _Documenta Philos. Arab._ Bonn., 1836, for Latin versions of select treatises). As we have already noted, his primary importance was as a teacher of logic. A great deal of what he has written is simply a reproduction of the outlines of the Aristotelian logic and an exposition of its principles, but De Vaux (_Avicenne_, pp. 94-97) has drawn attention to evidences of original thought in his “Letter in reply to certain questions.” Like al-Kindi he accepted the _Theology_ as a genuine work of Aristotle, and shows very clear traces of its influences. In his treatise “On the intelligence” he makes a careful analysis of the way in which the term _`aql_ (reason, intelligence, spirit) is employed in general speech and in philosophical enquiry. In common language “a man of intelligence” denotes a man of reliable judgment, who uses his judgment in an upright way to discern between good and evil, and thus is distinguished from a crafty man who employs his mind in devising evil expedients. Theologians use the term _`aql_ to denote the faculty which tests the validity of statements, either approving them as true or rejecting them as false. In the _Analytica_ Aristotle uses “intelligence” for the faculty by which man attains directly to the certain knowledge of axioms and general abstract truths without the need of proof; this faculty al-Farabi explains as being the part of the soul in which intuition exists, and which is thereby able to lay hold of the premises of speculative science, i.e., the reason of intelligence proper as the term is employed in the _de anima_, the rational soul which Alexander of Aphrodisias takes as an emanation from God. Following al-Kindi, al-Farabi speaks of four faculties or parts of the soul: the potential or latent intelligence, intelligence in action, acquired intelligence, and the agent intelligence. The first is the _`aql hayyulani_, the passive intelligence, the capacity which man has for understanding the essence of material things by abstracting mentally that essence from the various accidents with which it is associated in perception, more or less equivalent to the “common sense” of Aristotle. The intelligence in action or _`aql bi-l-fi`l_ is the potential faculty aroused to activity and making this abstraction. The agent intelligence or _`aql fa``al_ is the external power, the emanation from God which is able to awaken the latent power in man