i-iv. A survey of the teaching of categoriæ, prædicamenta, and interpretatio as preliminary begins with general advice (890 D). “The exposition of every book should be such as to furnish most readily the knowledge of what is written. No occasion should be sought of introducing difficulty; everywhere the way should be opened. That was the practise, I remember, of Abelard ... (891 A). Thus Porphyry should be read so that the significance of the expressions in question may be retained and the sense of the words got from the surface. He will be sufficiently introductory so, and conspicuous for being quickly intelligible ... (891 D). For the text is to be searched mannerly, not bitterly racked, as if it were a prisoner, until it gives up what it has not taken.” This preliminary closes with a reminiscence (900 C). “Bernard of Chartres used to say that we, like dwarfs on the shoulders of giants, can see more and farther not because we are keener and taller, but because of the greatness by which we are carried and exalted.” v-x. Forecasting the rest of the program, John wonders why Aristotle’s _Topica_ should have been so long neglected (903 A). “Single words of it, in both rules and examples, are valuable not only for _dialectica_, but for almost all the disciplines. It comprises eight books, each more potent than the last.” The following digest, book by book, iterates (910 C) the general value. “The precepts of all eloquence seem to be derived originally from it as from the primary source. For it is indubitably true, as Cicero and Quintilian say, that rhetors and rhetoricians have found in it not only an aid, but a source.” BOOK IV. _ANALYTICA_ In contrast to the ten long chapters of III, IV is divided into forty-two short ones: i-v, _analytica_ in general; vi-viii, _demonstrativa_; ix-xx, the progress of knowledge: sensus, imaginatio, prudentia, ratio, intellectus; xxi-xxiii, _hypothetica_, _sophistica_; xxiv-xlii, critical review: objectors to Aristotle the place of _logica_ in teaching, typical conceptions of ratio, and of truth and error, the relation of ratio to veritas. This last book iterates the importance of correlation (xxviii. 982 B). “But though _logica_ is useful generally, he who is ignorant of other arts[37] is not so much helped by it toward philosophy as he is hindered by a habit of verbosity and presumption. For _logica_ is almost useless if it be alone. It stands out when it shines by the power of correlated studies.”