and arouse it to activity, and the acquired intelligence or _`aql mustafad_ is the intelligence aroused to activity and developed under the inspiration of the agent intelligence. Thus the intelligence in action is related to the potential intellect as form is to matter, but the agent intelligence enters from outside, and by its operation the intelligence receives new powers, so that its highest activity is “acquired.” Al-Farabi appears throughout as a devout Muslim, and evidently does not appreciate the bearing of the Aristotelian psychology on the doctrine of the Qur´an. The earlier belief of Islam, as of most religions, was a heritage from primitive animism, which regarded life as due to the presence of a perfectly substantial, though invisible, thing called the soul: a thing is alive so long as the soul is present, it dies when the soul goes away. In the earlier forms of animism this is the explanation of all movement: the flying arrow has a “soul” in it so long as it moves, it ceases to move when this soul goes away or desires to rest. This involves no belief in the immortality of the soul, nor is the soul invested with any distinct personality, all that comes later; it is simply that life is regarded as a kind of substance, very light and impalpable but perfectly self-existent. What may be described as the “ghost” theory marks a later stage of evolution, when the departed soul is believed to retain a distinct personality and still to possess the form and some at least of the sensations associated with the being in which it formerly dwelt. Such was the stage reached by Arab psychology at the time of the preaching of Islam. The Aristotelian doctrine represented the soul as containing different energies or parts, such as it had in common with the vegetable world and such others as it possessed in common with the lower kinds of animals: that is to say the faculties of nutrition, reproduction, and all the perceptions obtained from the use of the organs of sense, as well as the intellectual generalisations derived from the use of those senses, are simply laid on one side as forms of energy derived from the potentialities latent in the material body, very nearly the position indeed of modern materialism, as the term is used in psychology. This does not oppose a belief in God, who is the prime source of the powers which exist, although that is brought out more by the commentators than by Aristotle himself; nor does it infringe the doctrine of an immortal and separable soul or spirit which exists in man in addition to what we may describe as the vegetative and animal soul. It is this spirit, the rational soul which has entered from outside and exists in man alone, which is immortal. Such a doctrine sets an impassible gulf between man and the rest of creation, and explains why it is impossible for those whose thought is formed on Aristotelian lines, whether in orthodox Islam or in the Catholic Church, to admit the “rights” of animals,