3 Again, adopting the [ideas of] shade and vacuity from Democritus and Epicurus, they have fitted these to their own views, following upon those [teachers] who had already talked a great deal about a vacuum and atoms, the one of which they called that which is, and the other that which is not. In like manner, these men call those things which are within the Pleroma real existences, just as those philosophers did the atoms; while they maintain that those which are without the Pleroma have no true existence, even as those did respecting the vacuum.
They have thus banished themselves in this world (since they are here outside of the Pleroma) into a place which has no existence. Again, when they maintain that these things [below] are images of those which have a true existence [above], they again most manifestly rehearse the doctrine of Democritus and Plato. For Democritus was the first who maintained that numerous and diverse figures were stamped, as it were, with the forms [of things above], and descended from universal space into this world.
But Plato, for his part, speaks of matter, and exemplar, and God. These men, following those distinctions, have styled what he calls ideas, and exemplar, the images of those things which are above; while, through a mere change of name, they boast themselves as being discoverers and contrivers of this kind of imaginary fiction.
Source: Adversus haereses (New Advent)