ights, to adorn the heaven by
their movements; on the second day, which is the fifth, birds and
fishes are called into being, to make beautiful the intermediate
element, for they move in air and water, which are here taken as one;
while on the third day, which is the sixth, animals are brought
forth, to move upon the earth and adorn it. It must also here be
noted that Augustine's opinion (Gen. ad lit. v, 5) on the production
of lights is not at variance with that of other holy writers, since
he says that they were made actually, and not merely virtually, for
the firmament has not the power of producing lights, as the earth has
of producing plants. Wherefore Scripture does not say: "Let the
firmament produce lights," though it says: "Let the earth bring forth
the green herb."

Reply Obj. 1: In Augustine's opinion there is no difficulty here; for
he does not hold a succession of time in these works, and so there
was no need for the matter of the lights to exist under another form.
Nor is there any difficulty in the opinion of those who hold the
heavenly bodies to be of the nature of the four elements, for it may
be said that they were formed out of matter already existing, as
animals and plants were formed. For those, however, who hold the
heavenly bodies to be of another nature from the elements, and
naturally incorruptible, the answer must be that the lights were
substantially created at the beginning, but that their substance, at
first formless, is formed on this day, by receiving not its
substantial form, but a determination of power. As to the fact that
the lights are not mentioned as existing from the beginning, but only
as made on the fourth day, Chrysostom (Hom. vi in Gen.) explains this
by the need of guarding the people from the danger of idolatry: since
the lights are proved not to be gods, by the fact that they were not
from the beginning.

Reply Obj. 2: No difficulty exists if we follow Augustine in holding
the light made on the first day to be spiritual, and that made on
this day to be corporeal. If, however, the light made on the first
day is understood to be itself corporeal, then it must be held to
have been produced on that day merely as light in general; and that
on the fourth day the lights received a definite power to produce
determinate effects. Thus we observe that the rays of the sun have
one effect, those of the moon another, and so forth. Hence, speaking
of such a determination of power, Diony