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Single Idea 1553

[filed under theme 6. Mathematics / A. Nature of Mathematics / 2. Geometry ]

Full Idea

No perceptible object is geometrically straight or curved; after all, a circle does not touch a ruler at a point, as Protagoras used to say, in arguing against the geometers.

Gist of Idea

No perceptible object is truly straight or curved

Source

Protagoras (fragments/reports [c.441 BCE], B07), quoted by Aristotle - Metaphysics 998a1

Book Ref

'The First Philosophers', ed/tr. Waterfield,Robin [OUP 2000], p.220

The 17 ideas from 'fragments/reports'

3305 There is no more purely metaphysical doctrine than Protagorean relativism [Benardete,JA on Protagoras]
1549 Everything that exists consists in being perceived [Protagoras]
3313 If my hot wind is your cold wind, then wind is neither hot nor cold, and so not as cold as itself [Benardete,JA on Protagoras]
3317 You can only state the problem of the relative warmth of an object by agreeing on the underlying object [Benardete,JA on Protagoras]
247 God is "the measure of all things", more than any man [Plato on Protagoras]
606 Protagoras absurdly thought that the knowing or perceiving man is 'the measure of all things' [Aristotle on Protagoras]
612 Relativists think if you poke your eye and see double, there must be two things [Aristotle on Protagoras]
6016 Early sophists thought convention improved nature; later they said nature was diminished by it [Protagoras, by Miller,FD]
1580 For Protagoras the only bad behaviour is that which interferes with social harmony [Protagoras, by Roochnik]
205 Protagoras contradicts himself by saying virtue is teachable, but then that it is not knowledge [Plato on Protagoras]
1659 Protagoras seems to have made the huge move of separating punishment from revenge [Protagoras, by Vlastos]
1552 He spent public money on education, as it benefits the individual and the state [Protagoras, by Diodorus of Sicily]
1545 Protagoras was the first to claim that there are two contradictory arguments about everything [Protagoras, by Diog. Laertius]
1551 He said he didn't know whether there are gods - but this is the same as atheism [Diogenes of Oen. on Protagoras]
1547 Man is the measure of all things - of things that are, and of things that are not [Protagoras]
1553 No perceptible object is truly straight or curved [Protagoras]
532 Successful education must go deep into the soul [Protagoras]