class of equivocal terms and assign thereto a special class-name, was an important step in logical procedure; and that step, among so many others, was made by Aristotle.[8] [Footnote 8: In the instructive commentary of Dexippus on the Categoriæ (contained in a supposed dialogue between Dexippus and his pupil Seleukus, of which all that remains has been recently published by Spengel, Munich, 1859), that commentator defends Aristotle against some critics who wondered why he began with these Ante-predicaments ([Greek: o(mô/numa, sunô/numa], &c.), instead of proceeding at once to the Predicaments or Categories themselves. Dexippus remarks that without understanding this distinction between _equivoca_ and _univoca_, the Categories themselves could not be properly appreciated; for Ens--[Greek: to\ o)\n]--is homonymous in reference to all the Categories, and not a Summum Genus, comprehending the Categories as distinct species under it; while each Category is a Genus in reference to its particulars. Moreover, Dexippus observes that this distinction of homonyms and synonyms was altogether unknown and never self-suggested to the ordinary mind ([Greek: o(/sôn ga\r e)/nnoian ou)k e)/chomen, tou/tôn pro/lêpsin ou)k e)/chomen], p. 20), and therefore required to be brought out first of all at the beginning; whereas the Post-predicaments (to which we shall come later on) were postponed to the end, because they were cases of familiar terms loosely employed, (See Spengel, Dexipp. pp. 19, 20, 21.)] Though Aristotle has professed to distinguish between terms implicated in predication, and terms not so implicated,[9] yet when he comes to explain the functions of the latter class, he considers them in reference to their functions as constituent members of propositions. He immediately begins by distinguishing four sorts of matters (_Entia_): That which is affirmable of a Subject, but is not in a Subject; That which is in a Subject, but is not affirmable of a Subject; That which is both in a Subject, and affirmable of a Subject; That which is neither in a Subject, nor affirmable of a Subject.[10] [Footnote 9: Aristot. Categor. p. 1, a. 16. [Greek: tô=n legome/nôn ta\ me\n kata\ sumplokê\n le/getai, ta\ d' a)/neu sumplokê=s; ta\ me\n ou)=n kata\ sumplokê\n oi(=on a)/nthrôpos tre/chei, a)/nthrôpos nika=|; ta\ d' a)/neu sumplokê=s oi)=on a)/nthrôpos, bou=s, tre/chei, nika=|.] It will be seen that the meaning and function of the single word can only explained relatively to the complete proposition, which must be assumed as foreknown. That which Aristotle discriminates in this treatise, in the phrases--[Greek: le/gesthai kata\ sumplokê\n] and [Greek: le/gesthai a)/neu sumplokê=s] is equivalent to what we read in the De Interpretatione (p. 16, b. 27, p. 17, a. 17) differently expressed, [Greek: phônê\ sêmantikê\ ô(s kata/phasis] and [Greek: phônê\ sêmantikê\ ô(s pha/sis].] [Footnote 10: Aristot. Categor. p. 1, a. 20.]