Letters 65.7

To these four Plato adds a fifth cause,—the pattern which he himself calls the “idea"; for it is this that the artist gazed upon when he created the work which he had decided to carry out. Now it makes no difference whether he has his pattern outside himself, that he may direct his glance to it, or within himself, conceived and placed there by himself. God has within himself these patterns of all things, and his mind comprehends the harmonies and the measures of the whole totality of things which are to be carried out; he is filled with these shapes which Plato calls the “ideas,”—imperishable, unchangeable, not subject to decay. And therefore, though men die, humanity itself, or the idea of man, according to which man is moulded, lasts on, and though men toil and perish, it suffers no change.

Seneca, Letters to Lucilius 65.7, translated by Richard Mott Gummere