Full Idea
The Platonists, on the basis of purely logical arguments, posit the existence of an indivisible 'triangle in itself'.
Gist of Idea
Platonists argue for the indivisible triangle-in-itself
Source
report of Plato (works [c.375 BCE]) by Aristotle - Coming-to-be and Passing-away (Gen/Corr) 316a15
A Reaction
A helpful confirmation that geometrical figures really are among the Forms (bearing in mind that numbers are not, because they contain one another). What shape is the Form of the triangle?
Book Reference
Democritus: 'Early Greek Phil VII: Democritus', ed/tr. Laks,A/Most,G [Harvard Loeb 2016], p.103