viii, text. 42, 43), after showing that the first mover is made up of
two parts, the moving and the moved, goes on to show the nature of
the union between these two parts. This, he says, is effected by
contact which is mutual if both are bodies; on the part of one only,
if one is a body and the other not. The Platonists explain the union
of soul and body in the same way, as a contact of a moving power with
the object moved, and since Plato holds the heavenly bodies to be
living beings, this means nothing else but that substances of
spiritual nature are united to them, and act as their moving power. A
proof that the heavenly bodies are moved by the direct influence and
contact of some spiritual substance, and not, like bodies of specific
gravity, by nature, lies in the fact that whereas nature moves to one
fixed end which having attained, it rests; this does not appear in
the movement of heavenly bodies. Hence it follows that they are moved
by some intellectual substances. Augustine appears to be of the same
opinion when he expresses his belief that all corporeal things are
ruled by God through the spirit of life (De Trin. iii, 4).

From what has been said, then, it is clear that the heavenly bodies
are not living beings in the same sense as plants and animals, and
that if they are called so, it can only be equivocally. It will also
be seen that the difference of opinion between those who affirm, and
those who deny, that these bodies have life, is not a difference of
things but of words.

Reply Obj. 1: Certain things belong to the adornment of the universe
by reason of their proper movement; and in this way the heavenly
luminaries agree with others that conduce to that adornment, for they
are moved by a living substance.

Reply Obj. 2: One being may be nobler than another absolutely, but
not in a particular respect. While, then, it is not conceded that the
souls of heavenly bodies are nobler than the souls of animals
absolutely it must be conceded that they are superior to them with
regard to their respective forms, since their form perfects their
matter entirely, which is not in potentiality to other forms; whereas
a soul does not do this. Also as regards movement the power that
moves the heavenly bodies is of a nobler kind.

Reply Obj. 3: Since the heavenly body is a mover moved, it is of the
nature of an instrument, which acts in virtue of the agent: and
therefore since this agent is a living substance the heaven