Aristotle (Metaph. E. i. p. 1025, b. 26) classifies the sciences as [Greek: theôrêtikai/, praktikai/, poiêtikai/]; next he subdivides the first of the three into [Greek: phusikê/, mathêmatikê/, prô/tê philosophi/a]. Brentano, after remarking that no place in this distribution is expressly provided for Logic, explains the omission as follows: "Diese auffallende Erscheinung erklärt sich daraus, dass diese [the three above-named theoretical sciences] allein das reelle Sein betrachten, und nach den drei Graden der Abstraktion in ihrer Betrachtungsweise verschieden, geschieden werden; während die Logik das bloss rationelle Sein, das [Greek: o(\n ô(s a)lêthe/s], behandelt." (Ueber die Bedeutung des Seienden nach Aristoteles, p. 39.)--Investigations [Greek: peri\ tê=s a)lêthei/as, o(\n tro/pon dei= a)pode/chesthai] are considered by Aristotle as belonging to [Greek: ta\ A)naluktika]; enquiries into method in the first instance, and into doctrine chiefly with a view to method (Metaphys. [Greek: G]. p. 1005, b. 2. In Metaphys. ]Greek: G]. 1005, b. 7, he declares that these enquiries into method, or analysis of the _principia_ of syllogistic reasoning, belong to the Philosophia Prima (compare Metaphys. Z. 12, p. 1037, b. 8). Schwegler in his Commentary (p. 161) remarks that this is one of the few passages in which Aristotle indicates the relation in which Logic stands to Metaphysics, or First Philosophy. The question has been started among his [Greek: A)pori/ai] Metaph. B. 2, p. 999, b. 30.] [Footnote 3: Respecting the title of Organon which was sometimes applied to the Analytica Posteriora only, see Waitz ad Organ, ii. p. 294.] These treatises are six in number:--1. Categoriæ;[4] 2. De Interpretatione, or De Enunciatione; 3. Analytica Priora; 4. Analytica Posteriora; 5. Topica; 6. De Sophisticis Elenchis. This last short treatise--De Sophisticis Elenchis--belongs naturally to the Topica which precedes it, and of which it ought to be ranked as the ninth or concluding book. Waitz has printed it as such in his edition of the Organon; but as it has been generally known with a separate place and title, I shall not depart from the received understanding. [Footnote 4: Some eminent critics, Prantl and Bonitz among them, consider the treatise Categoriæ not to be the work of Aristotle. The arguments on which this opinion rests are not convincing to me; and even if they were, the treatise could not be left out of consideration, since the _doctrine_ of the Ten Categories is indisputably Aristotelian. See Zeller, Die Phil. der Griech. ii. 2, pp. 50, 51, 2nd ed.]