The firmament's nature and the water above it

Then, when those who say these things are asked for the proof of sense perception, what do they answer? They say that because we have been accustomed to the sound from our first origin and have grown used to it from the beginning, we have lost the perception of it through long practice in hearing it—just like people in bronze workshops who have their ears struck continually. To refute the sophistry and rottenness of this argument, which is so plainly evident to everyone at first hearing, is not the work of a man who knows how to spare time or who aims at the understanding of his hearers. But let us leave the things of outsiders to outsiders and return to the ecclesiastical discourse.

Some of those before us have said that this is not the creation of a second heaven, but a further explanation of the first, because there the making of heaven and earth was handed down in summary, while here the Scripture hands down to us in more detailed fashion the manner in which each thing came to be. But we say that since a different name and a special function of the second heaven have been handed down, this one is other than the one made in the beginning, of a firmer nature, and providing an exceptional service to the whole.

And God said, “Let a firmament come into being in the midst of the water, and let it be separating between water and water.” And God made the firmament, and God separated between the water that was beneath the firmament and between the water that was above the firmament (Genesis 1:6-7). But before we touch the meaning of what is written, let us try to dissolve the objection brought against us by others. For they ask us: if the body of the firmament is spherical, as sight shows, and water is fluid and slips off high places, how could it have been made to sit firmly on the curved surface of the firmament? What then shall we say to this? That it is not at all necessary that what appears circular to us in its inner concavity should also have its outer surface finished spherically, and be perfectly turned and smoothly rounded throughout. For we see the stone roofs of baths and the construction of cave-like buildings, which are rounded into a semicircular shape on the inner view, yet often have a flat surface on the top of the roof. So for this reason let them neither make trouble for themselves nor cause trouble for us, as though we could not hold the water in the upper regions.

Next it would be right to say what the nature of the firmament is, and for what reason it was appointed to mediate between the waters. The name “firmament” is customary in Scripture for things that excel in strength. For example, when it says, “The Lord is my firmament and my refuge” (Psalm 17:3 LXX [Hebrew 18:2]), and “I have made firm its pillars” (Psalm 74:4 LXX [Hebrew 75:3]), and “Praise him in the firmament of his power” (Psalm 150:1 LXX [Hebrew 150:1]). Those outside call a solid body something dense and full, which is said in contrast to the mathematical. The mathematical is that which has its being only in dimensions—in breadth, I mean, and depth and height—while the solid is that which has resistance in addition to the dimensions. But it is customary for Scripture to call what is strong and unyielding a firmament, as it often uses this word even of air that has been greatly condensed, as when it says, “He who makes firm the thunder” (Job 37:4 LXX [Hebrew 37:4]).