Literal water above the firmament, not spiritual powers

What does he mean by this? He means complete dryness and the failure of the waters in the air, through which the earth has its power to bear fruit. So when he says that dew or rain is carried from heaven, we understand it as the waters that have been appointed to occupy the upper region. For when the exhalations gather in the heights, and the air is compressed by the force of the winds, the moisture that until then was scattered through the cloud in vapor-like, fine particles draws together, and drops form, carried downward by the weight of what has collected—and this is how rain comes to be. But when the moisture is made to foam, beaten back by the violence of the winds, and then is chilled to the utmost and frozen through and through, the cloud breaks apart and snow falls down. In short, by the same principle you can observe the whole nature of moisture taking shape in the air above our heads.

And let no one compare the simple and unadorned character of the spiritual words with the over-curious speculations of those who have philosophized about the heavens. For as much as the beauty of a chaste woman is to be preferred to that of a courtesan, so great is the difference between our words and those from outside. Those men impose a forced plausibility on their arguments; here the truth lies open, stripped of artifice. And why should we trouble ourselves to refute their falsehood, when it is enough to set their own books against one another and sit quietly as spectators of their war? For they are neither fewer in number nor inferior in rank, but they stand opposed to one another with great many-voicedness, some saying that the universe is consumed by fire and comes to life again from the seminal principles that remain in the burned remains—which is how they introduce endless destructions of the world and rebirths. But those men, splitting away from the truth on both sides, discover for themselves the paths of error in every direction.

But we also have a word to address to those from the Church concerning the separated waters—those who, on the pretext of anagogy and higher thoughts, have fled to allegories, saying that spiritual and incorporeal powers are figuratively signified by the waters: that the better powers remained above on the firmament, while the evil ones stayed below in the earthly and material regions. For this reason, they say, the waters above the heavens praise God—that is, the good powers, being worthy through the purity of their governing part, render fitting praise to the Creator. But the waters below the heavens, they say, are the spiritual powers of wickedness, which fell from their natural height into the depth of evil. Because they are turbulent and rebellious and tossed by the disturbances of the passions, they were named 'sea' on account of the changeableness and instability of their movements of choice.

Let us send such arguments away as comparisons of dreams and old wives' tales, and let us understand water as water, and let us accept the separation made by the firmament according to the reason already given. And indeed, even if the waters above the heavens are sometimes taken up for the praise of the common Lord of all, we do not therefore assign them a rational nature. For the heavens are not ensouled just because they declare the glory of God (Psalm 18:2 LXX), nor is the firmament a living, perceiving creature just because it announces the work of his hands (Psalm 18:2 LXX).