Respecting the logical distinction, which Aristotle places in the commencement of this treatise on the Categories--between predicates which are _affirmed of_ a Subject, and predicates which are _in_ a Subject[23]--we may remark that it turns altogether upon the name by which you describe the predicate. Thus he tells us that the Species and Genus (man, animal), and the Differentia (rational), may be _predicated of_ Sokrates, but are not _in_ Sokrates; while knowledge is _in_ Sokrates, but cannot be _predicated of_ Sokrates; and may be _predicated of_ grammar, but is not _in_ grammar. But if we look at this comparison, we shall see that in the last-mentioned example, the predicate is described by an abstract word (knowledge); while in the preceding examples it is described by a concrete word (man, animal, rational).[24] If, in place of these three last words, we substitute the abstract words corresponding to them--humanity, animality, rationality--we shall have to say that these are _in_ Sokrates, though they cannot (in their abstract form) be _predicated of_ Sokrates, but only in the form of their concrete paronyms, which Aristotle treats as a distinct predication. So if, instead of the abstract word knowledge, we employ the concrete word knowing or wise, we can no longer say that this is _in_ Sokrates, and that it may be _predicated of_ grammar. Abstract alone can be _predicated of_ abstract; concrete alone can be _predicated of_ concrete; if we describe the relation between Abstract and Concrete, we must say, The Abstract is _in_ the Concrete--the Concrete contains or embodies the Abstract. Indeed we find Aristotle referring the same predicate, when described by the abstract name, to one Category; and when described by the concrete paronymous adjective, to another and different Category.[25] The names Concrete and Abstract were not in the philosophical vocabulary of his day. In this passage of the Categoriæ, he establishes a distinction between predicates essential and predicates non-essential; the latter he here declares to be _in_ the Subject, the former not to be in it, but to be _co-efficients of_ its essence. But we shall find that he does not adhere to this distinction even throughout the present treatise, still less in other works. It seems to be a point of difference between the Categoriæ on one side, and the Physica and Metaphysica on the other, that in the Categoriæ he is more disposed to found supposed real distinctions on verbal etiquette, and on precise adherence to the syntactical structure of a proposition.[26] [Footnote 23: The distinction is expressed by Ammonius (Schol. p. 51, b. 46) as follows:--[Greek: ai( prô=tai ou)si/ai u(pokeu=ntai pa=sin, a)ll' ou)ch o(moi/ôs; toi=s me\n ga\r _pro\s u(/parxin_, tou/testi toi=s sumbebêko/sin, toi=s de\ _pro\s katêgori/an_, tou/testi tai=s katho/lou ou)si/ais.]] [Footnote 24: Ueberweg makes a remark similar to this.--System der Logik, sect. 56, note, p. 110, ed. second.]