Kindi has a fourfold division of the Spirit [17]: first the Spirit which is ever real,—the Cause and the Essence of all that is spiritual in the world,—thus without doubt God or the First Spirit produced; second, Spirit as the Reasoning capacity or Potentiality of the human soul; third, as the Habit or actual possession of the soul, which it can make use of at any moment, just as, for example, the writer can make use of his art; fourth and last, as Activity, by which a reality within the soul may be carried over to the reality that is without. The Activity last named appears, according to Kindi, to be the act of man himself, while to the First Cause,—to the ever-existing Spirit,—he ascribes the carrying of Potentiality into Habit, or the realisation of the Possible. The real Spirit or Mind we have thus received from above, and the third ʻaql is therefore called ʻaql mustafad, (Lat. intellectus adeptus sive adquisitus). The fundamental view of antiquity—that all our knowledge about things must come from a source outside of us—, runs, in the form of this doctrine of the ʻaql mustafad or Spirit which we receive from above, through the whole of Arabian Philosophy, and thence passes into Christian Philosophy. Unfortunately the theory is nearly correct, as far as this philosophy is itself concerned, for the ‘Active Spirit’, which has created it, is in reality the Neo-Platonic Aristotle. Man has always attributed to his God or Gods the highest of his own possessions. Muslim theologians directly attribute to the divine agency the moral actions of men. But in the opinion of the philosophers, Knowing is of more importance than Doing. The latter, having more to do with the lower world of the senses, may possibly be Man’s own; but his highest knowledge, the pure Reason, comes from above,—from the Divine Essence. It is clear that the doctrine of the Spirit, as it stands in Kindi, goes back to the ‘Nous’-doctrine of Alexander of Aphrodisias in his second book “On the Soul”. But Alexander expressly maintained that according to Aristotle there is a threefold ‘Nous’. Kindi says on the contrary that he is representing the opinion of Plato and Aristotle. In this the Neo-Pythagorean and the Neo-Platonic views unite: for in everything the number ‘Four’ must be pointed out, and Plato and Aristotle brought into agreement. 6. Let us now sum up: Kindi is a Mutazilite theologian and Neo-Platonic philosopher with Neo-Pythagorean additions. Socrates, the martyr of Athenian heathenism, is his ideal: on him, his fate and his teaching he has composed several works; and he seeks to combine Plato and Aristotle in Neo-Platonic fashion.