he 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.
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