Whether the firmament was made on the second day?

❌ Objection 1 : It would seem that the firmament was not made on the second day. For it is said (Gn. 1:8): "God called the firmament heaven." But the heaven existed before days, as is clear from the words, "In the beginning God created heaven and earth." Therefore the firmament was not made on the second day.

❌ Objection 2 : Further, the work of the six days is ordered conformably to the order of Divine wisdom. Now it would ill become the Divine wisdom to make afterwards that which is naturally first. But though the firmament naturally precedes the earth and the waters, these are mentioned before the formation of light, which was on the first day. Therefore the firmament was not made on the second day.

❌ Objection 3 : Further, all that was made in the six days was formed out of matter created before days began. But the firmament cannot have been formed out of pre-existing matter, for if so it would be liable to generation and corruption. Therefore the firmament was not made on the second day.