This criticism is of first importance for theology. Faith as well as reason demands a real relation between idea and ideate. The Christian student in the fifth century, familiar with Aristotle's criticism of Plato, would inevitably apply it in Christology. Any theory of redemption that ascribed duality to the Redeemer would seem to him to be open to the objections that Aristotle had urged against the theory of ideas. The Nestorian formula, in effect, juxtaposed the ideal Christ and the real Jesus, and left the two unrelated. This was Platonism in Christology. Aristotle's attack on Plato's system provided a radical criticism of Nestorianism. The monophysite theologians were blind to the difference between the Nestorian position and that of the orthodox. They saw that Aristotle had placed a powerful weapon in their hands, and they used it indifferently against both opposing parties. ARISTOTLE'S PSYCHOLOGY We turn now to Aristotle's psychology. We must give a brief sketch of it in order to establish the fact that the Aristotelian and the monophysite science of the soul labour under the same defect. It is a radical defect, namely, the almost complete absence of the conception of personality. The principle of Aristotle's psychology, like that of his metaphysic, is the concept of form and matter. The soul of man comes under the general ontological law. All existence is divisible into grades, the lower grade being the matter whose form is constituted by the next highest grade. Thus there is a graduated scale of being, starting from pure matter and rising to pure form. The inorganic is matter for the vegetable kingdom, the vegetable kingdom for the animal kingdom; the nutritive process is material for the sensitive, and the sensitive for the cognitive. Man is an epitome of these processes. The various parts of his nature are arranged in an ascending scale; form is the only cohesive force. The animal soul is the form of the body, born with it, growing with it, dying with it; the two are one in the closest union conceivable. Besides the soul of the body, there is, says Aristotle, a soul of the soul. This is reason, essentially different from animal and sensitive soul. It is not connected with organic function. It is pure intellectual principle. It is immaterial, immortal, the divine element in man. This reason is not a bare unity. As it appears in human experience, it is not full-grown. Potentially it contains all the categories, but the potentiality must be actualised. Consequently reason subdivides into active and passive intellect. The action of the former on the latter, and the response of the latter to the former, constitute the development of the mind, the education of the truth that is potentially present from the beginning.