3. METAPHYSICS.—Among all the Aristotelian writings, the Metaphysics is least entitled to be called a connected whole; it is only a connection of sketches, which, though they follow a certain fundamental idea, utterly fail of an inner mediation and a perfect development. We may distinguish in it seven distinct groups. (1) Criticism of the previous philosophic systems viewed in the light of the four Aristotelian principles, _Book_ I. (2) Positing of the apories or the philosophical preliminary questions, III. (3) The principle of contradiction, IV. (4) Definitions, V. (5) Examination of the conception of essence (οὐσία) and conceivable being (the τί ἦν εἴναι) or the conception of matter (ὕλη), form (εἶδος), and that which arises from the connection of these two (σύνολον), VII. VIII. (6) Potentiality and actuality, IX. (7) The Divine Spirit moving all, but itself unmoved, XII. (8) To these we may add the polemic against the Platonic doctrine of ideas and numbers, which runs through the whole Metaphysics, but is especially carried out in _Books_ XIII. and XIV. (1) _The Aristotelian Criticism of the Platonic Doctrine of Ideas._—In Aristotle’s antagonism to the Platonic doctrine of ideas, we must seek for the specific difference between the two systems, a difference of which Aristotle avails himself of every opportunity (especially _Metaph._ I. and XIII.) to express. Plato had beheld every thing actual in the idea, but the idea was to him a rigid truth, which had not yet become interwoven with the life and the movement of existence. Such a view, however, had this difficulty, the idea, however little Plato would have it so, found standing over against it in independent being the phenomenal world, while it furnished no principle on which the being of the phenomenal world could be affirmed. This Aristotle recognizes and charges upon Plato, that his ideas were only “immortalized things of sense,” out of which the being and becoming of the sensible could not be explained. In order to avoid this consequence, he himself makes out an original reference of mind to phenomenon, affirming that the relation of the two is, that of the actual to the possible, or that of form to matter, and considering also mind as the absolute actuality of matter, and matter, as the potentially mind. His argument against the Platonic doctrine of ideas, Aristotle makes out in the following way.