a less degree even in later times, the Aristotelian logic has been only second to grammar as the basis of a humane education. Al-Kindi's real influence is shown in the introduction of the problems of psychology and of metaphysics, and the work of the falasifa centres in these two studies on the lines indicated by al-Kindi.
In psychology, as we have seen, al-Kindi introduced a system already fully developed by Alexander and the neo-Platonic commentators on Aristotle, kept alive amongst the Syriac students of philosophy, and then further developed from this point by his successors. In metaphysics the circumstances were different. Al-Kindi apparently was the one who introduced the problems of metaphysics to the Muslim world, but it is obvious that he did not clearly understand Aristotle's treatment of these problems. The problems involved in the ideas of movement, time, and place are treated by Aristotle in books iv., v. and vii. of the Physics, which had been translated by al-Kindi's contemporary, Hunayn b. Ishaq, and in the Metaphysics, of which at the time no Arabic translation existed, so that, so far as it was used, al-Kindi must have consulted the Greek text.
The essay "On the Five Essences" treats the ideas of the five conditions of matter, form, movement, time, and place. Of these he defines (a) matter as that which receives the other essences but cannot itself be received as an attribute, and so if the matter is taken away the other four essences are necessarily
