The Republic by Plato Part 7 Page 33

Yes.

Whereas the thinking mind, intending to light up the chaos, was compelled to reverse the process, and look at small and great as separate and not confused.

Very true.

Was not this the beginning of the enquiry ‘What is great?’ and ‘What is small?

Exactly so.

And thus arose the distinction of the visible and the intelligible.

Most true.

This was what I meant when I spoke of impressions which invited the intellect, or the reverse — those which are simultaneous with opposite impressions, invite thought; those which are not simultaneous do not.