is thus a natural history of finite thought. Because it is a knowledge and consciousness of the abstract activity of pure understanding, it is not a knowledge of this and that concrete fact, being pure form. This knowledge is in fact marvellous, and even more marvellous is the manner in which it is constituted: this logic is hence a work which does the greatest honour to the deep thought of its discoverer and to the power of his abstraction. For the greatest cohesive power in thought is found in separating it from what is material and thus securing it; and the strength shows itself almost more, if thus secured when it, amalgamated with matter, turns about in manifold ways and is seen to be capable of numberless alterations and applications. Aristotle also considers, in fact, not only the movement of thought, but likewise of thought in ordinary conception. The Logic of Aristotle is contained in five books, which are collected together under the name Ὀργανον. _a._ The Categories (κατηγορίαι), of which the first work treats, are the universal determinations, that which is predicated of existent things (κατηγορεῖται): as well that which we call conceptions of the understanding, as the simple realities of things. This may be called an ontology, as pertaining to metaphysics; hence these determinations also appear in Aristotle’s Metaphysics. Aristotle (Categor. I.) now says: “Things are termed homonyms (ὁμώνυμα) of which the name alone is common, but which have a different substantial definition (λόγος τῆς οὐσίας); thus a horse and the picture of a horse are both called an animal.”