Enneads II.4: Of Matter
Matter Is Nothing Composite, but by Nature Simple and One
8. What then is this matter which is one, continuous, and without qualities? Evidently, it could not be a body, since it has no quality; if it were a body, it would have a quality. We say that it is the matter of all sense-objects, and not the matter of some, and the form of others, just as clay is matter, in respect to the potter, without being matter absolutely (as thought Aristotle). As we are not considering the matter of any particular object, but the matter of all things, we would not attribute to its nature anything of what falls under our senses—no quality, color, heat, cold, lightness, weight, density, sparseness, figure or magnitude; for magnitude is something entirely different from being large, and figure from the figured object. Matter therefore is not anything composite, but something simple, and by nature one (according to the views of Plato and Aristotle combined). Only thus could matter be deprived of all properties (as it is).
MATTER AND THE INFORMING PRINCIPLE MUST BE CONTEMPORARIES TO ACCOUNT FOR THEIR MUTUAL RELATIONS.
The principle which informs matter will give it form as something foreign to its nature; it will also introduce magnitude and all the real properties. Otherwise, it would be enslaved to the magnitude of matter, and could not decide of the magnitude of matter, and magnitude would be dependent on the disposition of matter. A theory of a consultation between it and the magnitude of matter would be an absurd fiction. On the contrary, if the efficient cause precede matter, matter will be exactly as desired by the efficient cause, and be capable of docilely receiving any kind of form, including magnitude. If matter possessed magnitude, it would also possess figure, and would thus be rather difficult to fashion. Form therefore enters into matter by importing into it (what constitutes corporeal being); now every form contains a magnitude and a quantity which are determined by reason (“being”), and with reason. That is why in all kinds of beings, quantity is determined only along with form; for the quantity (the magnitude) of man is not the quantity of the bird. It would be absurd to insist on the difference between giving to matter the quantity of a bird, and impressing its quality on it, that quality is a reason, while quantity is not a form; for quantity is both measure and number.