The meaning of -istic (was: Platonistic

From online etymological:

"-istic"

adj. suffix, from Latin "-isticus" (often via French "-istique"), from Greek "-istikos", which is adj. suffix "-ikos" added to n. suffix "-istes" (see "-ist").

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So it seems you need a Platonist (is Plato a Platonist?) -- and then go -ic. Whereas if you grant that Plato is Platonic rather than a Platonist, you stay there ("platonic"). Or something.