Procli Diadochi In Primum Euclidis Elementorum Librum Commentarii

it will provide the more holistic principles to some, and the more particular to others. For this reason, Socrates in the Theaetetus a dialogue by Plato concerning the nature of knowledge, mingling play with earnestness, compares the kinds of knowledge within us to birds. He says that some fly in flocks, while others fly separately from the rest. For the more common and holistic knowledges contain many more particular ones within themselves, while those that grasp the things known by their eide forms/species stand apart from one another and are disconnected, having started from differing first principles. Let one science, therefore, be placed before the many sciences and studies: the one that knows the common things running through all genera, and which provides the principles for all mathematical sciences.

15 And let the teaching concerning it be limited to this point within us. After this, let us consider what the criterion of the mathematical sciences might be, and let us establish it. As a guide for this transmission, let us take Plato, who in the Republic divides the things known, and separately assigns the knowledges in correspondence with the things known. For having posited that of existing things, some are noēta intelligible and others are aisthēta sensible; and of the intelligible things, some are again intelligible while others are dianoēta discursive/mathematical; and of the sensible things, some are sensible while others are eikasta likenesses/images; he sets knowledge of noēsis intellection over the intelligible things, which are the most primary of the four genera, dianoia discursive thought over the discursive things, pistis belief over the sensible things, and eikasia imagination over the likenesses. And he declares that eikasia bears the same ratio to aisthesis sense-perception as dianoia does to noēsis.