II.1 chapter 33

So what gives sufficient reason to state that with the creation of the light the creation of angels is meant?
From the Bible it is clear that there are two kinds of angels: the holy angels and the fallen angels, and they are clearly referred to with the words of light and darkness. No one can deny that there was a separation of the angels either in foreknowledge or in act by God.
Well, even if we have not stated the meaning of the author, even then our way of thought is not without use, because we have followed the rule of faith (which is possible even in the description of the corporeal things in creation, like the apostle Paul speaks about the children of the light opposing the day to the night) and only said which agrees with other Bible places. But we may suppose to have stated the meaning of the author, or rather of the Holy Spirit, because all works of God were said to be finished in six days and we may suppose that none of them were omitted from the description.