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1 Geometry (and mathematics) is inevitably less abstract than dialectics. But the special purpose of the Platonic education values mathematics chiefly as a discipline in abstraction. Cf. on 523 A, p. 152, note b; and Titchener, A Beginner's Psychology, pp. 265-266: “There are probably a good many of us whose abstract idea of ‘triangle’ is simply a mental picture of the little equilateral triangle that stands for the word in text-books of geometry.” There have been some attempts to prove (that of Mr. F. M. Cornford in Mind,April 1932, is the most recent) that Plato, if he could not anticipate in detail the modern reduction of mathematics to logic, did postulate something like it as an ideal, the realization of which would abolish his own sharp distinction between mathematics and dialectic. The argument rests on a remote and strained interpretation of two or three texts of the Republic(cf. e.g. 511 and 533 B-D) which, naturally interpreted, merely affirm the general inferiority of the mathematical method and the intermediate position for education of mathematics as a propaedeutic to dialectics. Plato's purpose throughout is not to exhort mathematicians as such to question their initiatory postulates, but to mark definitely the boundaries between the mathematical and other sciences and pure dialectics or philosophy. The distinction is a true and useful one today. Aristotle often refers to it with no hint that it could not be abolished by a new and different kind of mathematics. And it is uncritical to read that intention into Plato's words. He may have contributed, and doubtless did contribute, in other ways to the improvement and precision of mathematical logic. But he had no idea of doing away with the fundamental difference that made dialectics and not mathematics the coping-stone of the higher education—science as such does not question its first principles and dialectic does. Cf. 533 B-534 E.
3 Cf. Polit. 302 E, Laws 757 E, 818 B, Phileb. 62 B, Tim. 69 D, and also on 494 A. The word ἀναγκαίως has been variously misunderstood and mistranslated. It simply means that geometers are compelled to use the language of sense perception though they are thinking of abstractions (ideas) of which sense images are only approximations.
4 Cf. Aristot.Met. 1051 a 22εὑρίσκεται δὲ καὶ τὰ διαγράμματα ἐνεργείᾳ: διαιροῦντες γὰρ εὑρίσκουσιν, “geometrical constructions, too, are discovered by an actualization, because it is by dividing that we discover them.” (Loeb tr.)
6 Cf. Thompson on Meno 87 A.
7 E. Hoffmann, Der gegenwärtige Stand der Platonforschung, p. 1091 (Anhang, Zeller, Plato, 5th ed.), misunderstands the passage when he says: “Die Abneigung Platons, dem Ideellen irgendwie einen dynamischen Charakter zuzuschreiben, zeigt sich sogar in terminologischen Andeutungen; so verbietet er Republ. 527 A für die Mathematik jede Anwendung dynamischer Termini wie τετραγωνίζειν, παρατείνειν, προστιθέναι” Plato does not forbid the use of such terms but merely recognizes their inadequacy to express the true nature and purpose of geometry.
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