As regards empirical psychology he has anxiously endeavoured to keep by Aristotle, in opposition to Galen and others; but in the doctrine of the “nous” he diverges from his master not inconsiderably, without being aware of it. His conception,—springing from Neo-Platonic views,—of the Material Reason, is peculiar. It is not a mere aptitude or capacity of the human soul, neither is it equivalent to the sensuous-spiritual life of presentation, but it is something above the soul, and above the individual. The Material Reason is eternal, imperishable Spirit, as eternal and imperishable as the pure Reason or the Active Spirit over us. The ascription of a separate existence to Matter in the domain of the corporeal, is here transferred by Ibn Roshd,—following of course Themistius and others,—to the region of the spiritual. The Material Reason is thus eternal substance. The natural aptitudes, or the capacity of the human individual for intellectual knowledge Ibn Roshd denominates the Passive Reason. That comes into being and disappears, with men as individuals, but the Material Reason is eternal, like Man as a race. But a measure of obscurity remains, and it could hardly have been otherwise, about the relation between the Active Spirit and the Receptive Spirit, (if we may for the time use this last term for the Material Reason). The Active Spirit renders intelligible the presentations of the human soul, while the Receptive Spirit absorbs these intelligibilia. The life of the soul in individual men thus forms the meeting-place of this mystic pair of lovers. And such places differ very greatly. It depends on the entire capacity of a man’s soul, and on the disposition of his perceptions, in what degree the Active Spirit can elevate these to intelligibility, and how far the Receptive Spirit is in a position to make them a portion of its own contents. This explains why men are not all at the same stage of spiritual knowledge. But the sum of spiritual knowledge in the world continues unaltered, although the partition of it undergoes individual variations. By a necessity of nature, the Philosopher re-appears, without fail, whether an Aristotle or an Ibn Roshd, in whose brain Being becomes Idea. It is true that the thoughts of individual men occur in the element of time, and that the Receptive Spirit is changeable, so far as the individual has a part in it; but considered as the Reason of the Human Race, that Spirit is eternally incapable of change, like the Active Spirit from the last Sphere above us.