Now what is it that Aristotle here means by "exoteric discourse?" We may discover by reading the matter comprised between the two foregoing citations. We find a string of perplexing difficulties connected with the supposition that Time exists: such as, "That all Time is either past or future, of which the former no longer exists, and the latter does not yet exist; that the Now is no part of Time, for every Whole is composed of its Parts, and Time is not composed of Nows," &c. I do not go farther here into these subtle suggestions, because my present purpose is only to illustrate what Aristotle calls "exoteric discourse," by exhibiting what he himself announces to be a specimen thereof. It is the process of noticing and tracing out all the doubts and difficulties ([Greek: a)pori/as]) which beset the enquiry in hand, along with the different opinions entertained about it either by the vulgar, or by individual philosophers, and the various reasons whereby such opinions may be sustained or impugned. It is in fact the same process as that which, when performed (as it was habitually and actively in his age) between two disputants, he calls _dialectic debate_; and which he seeks to encourage as well as to regulate in his treatise entitled Topica. He contrasts it with philosophy, or with the strictly didactic and demonstrative procedure: wherein the teacher lays down principles which he requires the learner to admit, and then deduces from them, by syllogisms constructed in regular form, consequences indisputably binding on all who have admitted the principles. But though Aristotle thus distinguishes Dialectic from Philosophy, he at the same time declares it to be valuable as an auxiliary towards the purpose of philosophy, and as an introductory exercise before the didactic stage begins. The philosopher ought to show his competence as a dialectician, by indicating and handling those various difficulties and controversies bearing on his subject, which have already been made known, either in writings or in oral debate.[40] [Footnote 40: See Aristot. Topic. i. p. 100, b. 21, p. 101, a. 25, 34-36, b. 2. [Greek: Pro\s de\ ta\s kata\ philosophi/an e)pistê/mas (chrê/simos ê( pragmatei/a), o(/ti duna/menoi pro\s a)mpho/tera diaporê=sai r(a=|on e)n e(ka/stois katopso/metha ta)lêthe/s te kai\ to\ pseu=dos], p. 105, b. 30. [Greek: Pro\s me\n ou)=n philosophi/an kat' a)lêtheian peri\ **au)tô=n pragmateue/on, _**dialektikô=s de\ pro\s do/xan_.] Compare also the commencement of book B. in the Metaphysica, p. 995, a. 28 seq., and, indeed, the whole of book B., which contains a dialectic discussion of numerous [Greek: a)pori/ai]. Aristotle himself refers to it afterwards ([Greek: G]. p. 1004, a. 32) in the words [Greek: u(/per e)n tai=s a)pori/ais e)lechthê].