Definition of "Platonist"

[St Augustine of Hippo] became of a Maniche, and of a platoniste a good christian.

1549, Hugh Latimer, The Seconde Sermon... Preached before the Kynges Maiestie

I suspect that in their hearts most working mathematicians are Platonists, in that they take it as a matter of unassailable if unprovable fact that mathematical reality stands apart from the world, and is at least as real as the world, and possibly gives shape to the world, as Plato suggested.

1992 March 2, Richard Preston, “The Mountains of Pi”, in The New Yorker