Considered in itself, then, it is in potentiality in respect to all those forms to which it is common, and in receiving any one form it is in act only as regards that form. Hence it remains in potentiality to all other forms. And this is the case even where some forms are more perfect than others, and contain these others virtually in themselves. For potentiality in itself is indifferent with respect to perfection and imperfection, so that under an imperfect form it is in potentiality to a perfect form, and vice versa. Matter, therefore, whilst existing under the form of an incorruptible body, would be in potentiality to the form of a corruptible body; and as it does not actually possess the latter, it has both form and the privation of form; for want of a form in that which is in potentiality thereto is privation. But this condition implies corruptibility. It is therefore impossible that bodies by nature corruptible, and those by nature incorruptible, should possess the same matter.
Neither can we say, as Averroes [*De Substantia Orbis ii.] imagines, that a heavenly body itself is the matter of the heaven—being in potentiality with regard to place, though not to being, and that its form is a separate substance united to it as its motive force. For it is impossible to suppose any being in act, unless in its totality it be act and form, or be something which has act or form. Setting aside, then, in thought, the separate substance stated to be endowed with motive power, if the heavenly body is not something having form—that is, something composed of a form and the subject of that form—it follows that in its totality it is form and act. But every such thing is something actually understood, which the heavenly bodies are not, being sensible. It follows, then, that the matter of the heavenly bodies, considered in itself, is in potentiality to that form alone which it actually possesses. Nor does it concern the point at issue to inquire whether this is a soul or any other thing. Hence this form perfects this matter in such a way that there remains in it no potentiality with respect to being, but only to place, as Aristotle [*De Coelo i, text. 20] says. So, then, the matter of the heavenly bodies and of the elements is not the same, except by analogy, in so far as they agree in the character of potentiality.
Reply Obj. 1: Augustine follows in this the opinion of Plato, who does not admit a fifth essence. Or we may say that formless matter is one with the unity of order, as all bodies are one in the order of corporeal creatures.
Reply Obj. 2: If genus is taken in a physical sense, corruptible and incorruptible things are not in the same genus, on account of their different modes of potentiality, as is said in Metaph. x, text. 26. Logically considered, however, there is but one genus of all bodies, since they are all included in the one notion of corporeity.
Reply Obj. 3: The form of corporeity is not one and the same in all bodies, being no other than the various forms by which bodies are distinguished, as stated above.
Reply Obj. 4: As potentiality is directed towards act, potential beings are differentiated by their different acts, as sight is by color, hearing by sound. Therefore for this reason the matter of the celestial bodies is different from that of the elemental, because the matter of the celestial is not in potentiality to an elemental form. _______________________
THIRD ARTICLE [I, Q. 66, Art. 3]
Whether the Empyrean Heaven Was Created at the Same Time As Formless
Matter?
Objection 1: It would seem that the empyrean heaven was not created at the same time as formless matter. For the empyrean, if it is anything at all, must be a sensible body. But all sensible bodies are movable, and the empyrean heaven is not movable. For if it were so, its movement would be ascertained by the movement of some visible body, which is not the case. The empyrean heaven, then, was not created contemporaneously with formless matter.
Obj. 2: Further, Augustine says (De Trin. iii, 4) that "the lower bodies are governed by the higher in a certain order." If, therefore, the empyrean heaven is the highest of bodies, it must necessarily exercise some influence on bodies below it. But this does not seem to be the case, especially as it is presumed to be without movement; for one body cannot move another unless itself also be moved. Therefore the empyrean heaven was not created together with formless matter.