Marsilio Ficino’s Platonic Theology, Volume I

27On Aristotle's authority, Averroes proves that the corporeal and substantial form of the heavens lacks matter, because there is there no potency toward diverse forms, which is the proper nature of matter. Dimension nevertheless exists there, and he judges that a form of this kind stands midway between natural and divine forms: natural forms exist with matter and quantity, divine forms are wholly free of both, and the form of the heavens is intermediate between the two, lest one pass from extreme to extreme without a middle. He therefore judges it fitting that this form should exist with quantity, but without matter. From this we argue as follows. Since substantial form is ordinarily seated in matter rather than in quantity, and in the order of its genus and nature has a greater proportion to matter than to quantity, if it can exist somewhere without matter, much more can it subsist somewhere apart from quantity.

28Moreover, as Proclus holds, there are three kinds of bodies. Some, to use his words, are at once material and composite, such as those composed from the four elements. Then there are the spheres of the elements, material indeed but in a certain way simple. Finally, there are celestial bodies, at once simple and immaterial. He also posits three kinds of forms, no differently from Averroes. For he wishes the general definition of forms to be this: a form is that by which something exists and acts distinctly and actually. No dimensions at all are included in this definition, though a subject may perhaps be signified in a certain way when it says “by which something,” and in what follows. Hence he concludes that, if there are forms without underlying matter, as celestial forms are, then it is all the more possible—and necessary—for far more forms to exist without dimension.