and defective they may seem to us, yet made the ruler admit that he was subordinate to a system, and defined the limits allowed by that system in conformity with ideals of equity and justice. It is interesting to note that in Ibn Sina’s time mystic theology had already taken its place as a subject of serious study. A short time afterwards a philosopher named an-Natali arrived at Bukhara and became a guest of Ibn Sina’s father. Bearing in mind the technical meaning of _failasuf_, we recognise this guest as a professed Aristotelian, and presumably one able to obtain his living as a teacher of the Aristotelian doctrine. From him Ibn Sina learned logic and had his mind directed towards the Aristotelian teaching, which was then preached like a religion. After this he studied Euclid, the _Almagesta_, and the “Aphorisms of the Philosophers.” His next study was medicine, in which he made so great progress that he adopted the practice of medicine as his profession. He attempted to study Aristotle’s _Metaphysics_, but found himself entirely incapable of understanding its meaning, until one day he casually purchased one of al-Farabi’s books, and by its help he was able to grasp the meaning and purport of what had so far eluded him. It is on this ground that we are entitled to describe Ibn Sina as a pupil of al-Farabi: it was al-Farabi’s work which really formed his mind and guided him to the interpretation of Aristotle; al-Farabi was, in the truest sense, the parent of all subsequent Arabic philosophers; great as was Ibn Sina he does not enter into the tradition in the same way as al-Farabi, and does not exercise the same influence on his successors, although al-Ghazali classes him with al-Farabi, and calls them the leading interpreters of Aristotle. Emphasis is sometimes laid upon the fact that Ibn Sina treats philosophy as quite apart from revelation as given in the Qur´an; but in this he was not original: it was the general tendency of all who came after al-Farabi; we can only say that Ibn Sina was the first important writer who illustrates this tendency.