The firmament is solid but not ice or crystal

Scripture speaks of the solidity and resistance of the wind that is caught in the hollows of the clouds. When that wind bursts out violently, it produces the sounds of thunder. Scripture called this force the making firm of thunder (Amos 4:13). Basil says we hold that this utterance about the firmament has been appointed for a different purpose: for a solid nature strong enough to hold back what is slippery and easily dissolved in water.

That does not mean we should suppose the firmament looks like frozen water, merely because the common view holds that it takes its origin from water. Nor should we suppose it is made of some matter that begins when moisture is filtered, like crystal stone or like the mica that forms in mines. People say water is changed into crystal stone by extreme freezing. Mica is a transparent stone with its own very pure clearness. If a piece is found true to its nature, neither eaten away by any decay nor split through its depth by cracks, its brightness is almost like air. Basil says we liken the firmament to none of these things. To hold such notions about heaven is truly the mark of a childish and simple mind. It is true that all things are in all things: fire is in earth, air is in water, and each of the other elements is likewise in another. None of the elements perceived by the senses is pure and unmixed, whether by sharing in what tends toward the middle or in what tends toward its opposite. For that reason Basil says we do not accept saying that the firmament either comes from one of the simple elements or is a mixture made from them. Scripture has taught us to allow our minds to imagine nothing beyond what has been granted.

Basil says we should not pass over one point without marking it. After God gave the command, “Let there be a firmament” (Genesis 1:6), Scripture does not simply add, “and there was a firmament.” It says instead, “And God made the firmament” (Genesis 1:7), and again, “God divided.” Scripture says, “You deaf, hear, and you blind, look up” (Isaiah 42:18). Basil asks who is deaf except the one who does not hear the Spirit crying out so loudly. And who is blind except the one who does not see such clear proofs concerning the only Son. “Let there be a firmament” is the voice of the preliminary cause. “God made the firmament” bears witness to his making and fashioning power.

But Basil says let us return our speech to the course of the explanation. God says, “Let it be dividing between water and water” (Genesis 1:6). The outpouring of the waters was boundless, it seems, surging over the earth from every side and hanging above it, so that it seemed to exceed its due proportion to the other elements. For this reason it was said earlier that the earth was clothed all around by the deep. Basil says he will give the reason for this abundance later. Certainly none of you will object to this account as if it assumed impossible or invented things, not even those among you whose minds are highly trained and keenly observant of this perishable and fleeting nature. Nor will you demand from us an account of what the nature of the waters rested upon. By the same reasoning by which they hold the earth suspended in the middle, though it is heavier than water, drawing it away from the outermost bounds, they will surely also grant that the countless water rests motionless around the earth, both because it naturally moves downward and because it is evenly balanced on every side.