Plato discusses a Socratic "dream" at length in Theaetetus, that is to say, the perceivable primary elements of complex are unaccountable and unknowable, whereas the complex are both knowable and expressible. He also talks about a kind of description about paths to the whole through the elements. Although these discussions ended with the denial of a third definition of knowledge, the insights contained in these discussions are fully absorbed by Aristotle into his method of definition of complex, which composed of matter as element and form as path. So in my opinion, definition of complex in Aristotle's Metaphysics ΖΗ is perhaps under the positive influence elements and paths in Plato's Theaetetus.