The extremes imply the middle; do not probe the substance of heaven or earth

And certainly whatever lies between these two also came into being together with the extremes. So even if Moses says nothing about the elements—fire, water, and air—you should understand by your own reasoning, first, that all things are mixed with all things. In earth you will find water, air, and fire: fire leaps out from stones, and from iron—which itself has its origin from the earth—abundant fire is wont to flash forth in friction. This is worth marveling at: fire exists within bodies and lurks there without harm, but once it is called outside, it is destructive of those guarding it for a time. Well-diggers show that the nature of water is present in the earth, and the vapors rising from earth moistened and warmed by the sun show the presence of air. Then further, if heaven by nature occupies the upper region and the earth is the lowest—because light things are carried toward heaven, while heavy things naturally sink down toward the earth, and up and down are most opposite to each other—then the one who mentioned the things most distant from each other by nature also indicated by synecdoche the things that fill the space between them. So do not seek an explanation of each individual thing, but understand what was passed over in silence through what was spoken.

“In the beginning God made the heaven and the earth.” The investigation of the substance of each existing thing—whether of those that fall under our contemplation or of those set before our senses—would introduce a long and detached discourse into the exposition, so that more words would be consumed in examining this problem than all the rest that can be said about each of the questions. And this would be of no benefit for the building up of the Church. But concerning the substance of heaven, we are satisfied with what Isaiah said. In simple words he gave us an adequate understanding of its nature when he said, “He who made firm the heaven as smoke” (Isaiah 40:22)—that is, he gave the heaven a fine nature for its composition, not a solid nor thick one. And concerning its shape, what he said is sufficient for us, when he said in praise of God, “He who set the heaven as a vault” (Isaiah 40:22). Let us give ourselves the same counsel concerning the earth: not to busy ourselves overmuch with its substance, whatever it may be, nor to wear ourselves out with reasonings by seeking out the underlying reality itself, nor to seek some nature devoid of qualities, existing without quality by its own definition. Rather, we should know well that everything observed about the earth is ordered toward the principle of its being, and these things complete its substance. For you will arrive at nothing if you try by reasoning to strip away each of the qualities that exist in it. If you remove the black, the cold, the heavy, the dense, the qualities of taste that exist in it, or any others that are observed about it, there will be no underlying reality left. So I urge you to leave these questions aside, and not to seek on what the earth stands. For the mind will grow dizzy this way too, as the reasoning proceeds toward no agreed-upon end.