These remarks serve partly to meet the difficulties pointed out by commentators in regard to the Ten Categories. From the century immediately succeeding Aristotle, down to recent times, the question has always been asked, why did Aristotle fix upon Ten Categories rather than any other number? and why upon these Ten rather than others? And ancient commentators[68] as well as modern have insisted, that the classification is at once defective and redundant; leaving out altogether some particulars, while it enumerates others twice over or more than twice. (This last charge is, however, admitted by Aristotle himself, who considers it no ground of objection that the same particular may sometimes be ranked under two distinct heads.) The replies made to the questions, and the attempts to shew cause for the selection of these Ten classes, have not been satisfactory; though it is certain that Aristotle himself treats the classification as if it were real and exhaustive,[69] obtained by comparing many propositions and drawing from them an induction. He tries to determine, in regard to some particular enquiries, under which of the Ten _Summa Genera_ the subject of the enquiry is to be ranged; he indicates some predicate of extreme generality (_Unum_, _Bonum_, &c.), which extend over all or several Categories, as equivocal or analogous, representing no true _Genera_. But though Aristotle takes this view of the completeness of his own classification, he never assigns the grounds of it, and we are left to make them out in the best way we can. [Footnote 68: Schol. p. 47, b. 14, seq., 49, a. 10, seq. Br.; also Simplikius ad Categor. fol. 15, 31 A, 33 E. ed. Basil., 1551.] [Footnote 69 Scholia ad Analyt. Poster. (I. xxiii. p. 83, a. 21) p. 227, b. 40, Br. [Greek: O(/ti de\ tosau=tai mo/nai ai( katêgori/ai ai( kata\ tô=n ou)siô=n lego/menai, e)k tê=s e)pagôgê=s lamba/nei.] Brentano (in his treatise, Ueber die Bedeutung des Seienden in Aristoteles, Sects. 12 and 13, pp. 148-177) attempts to draw out a scheme of systematic deduction for the Categories. He quotes (pp. 181, 182) a passage from Thomas Aquinas, in which such a scheme is set forth acutely and plausibly. But if Aristotle had had any such system present to his mind, he would hardly have left it to be divined by commentators. Simplikius observes (Schol. ad Categ. p. 44, a. 30) that the last nine Categories coincide in the main (excepting such portion of _Quale_ as belongs to the Essence) with [Greek: to\ o)/n kata\ sumbebêko/s]: which latter, according to Aristotle's repeated declarations, can never be the matter of any theorizing or scientific treatment--[Greek: ou)demi/a e)sti\ peri\ au)to\ theôri/a], Metaphys. E. p. 1026, b. 4; K. p. 1064, b. 17. This view of Aristotle respecting [Greek: to\ sumbebêko/s], is hardly consistent with a scheme of intentional deduction for the accidental predicates.]