Book I of Meteora

...were filled as water rushed into them through the vacuities. But now this does not happen because they are full of air, and this cannot be expelled because their mouths are blocked by the water. There are, furthermore, countless other things by which this is demonstrated, of which it is not necessary to speak now. Therefore, there cannot be a void within the world. Aristotle and those who follow his sect do not even allow there to be a void outside the world. For they say that a void must be a vessel of a body. But outside the world there is no body, wherefore there is no void. But this is truly foolish and absurd, just as if someone were to say that because water cannot exist in arid and waterless places, it is impossible for there to be a vessel there that could receive water. Therefore, we must know that a vessel of a body is spoken of in two ways: one, when it has a body and is filled by it; the other, when it does not yet have a body, but can have one. "But," they say, "if there were a void outside the world, the world would be carried through it, having nothing that could contain and support it." We shall say that it is impossible to be carried through the void. For it inclines toward its own middle. And it holds this to be downward, toward which it inclines. If the world did not have the same center and "down," it could indeed have been carried through the void, as will be demonstrated in the discussion concerning motion toward the center. And that also is said by them: if...

...were filled, as water slipped into them through the vacuities. But now this does not happen: because they are full of air, which cannot burst out, because their mouths are obstructed by the water. There are besides innumerable other things by which this is demonstrated, about which it is now not necessary to speak. In the world, therefore, there cannot be a void. Aristotle and those who follow his school do not even permit there to be a void outside the world. For it is necessary, they say, that the void be a vessel of a body. But outside the world there is no body, so there is no void. But this is truly foolish and silly, just as if someone were to say that because water cannot exist in dry places destitute of moisture, there is not even a vessel there that could receive water. It is necessary, therefore, for us to know that a vessel of a body is spoken of in two ways: one, when it has a body by which it is filled; the other, when it does not yet have a body, but is able to have one. "But," they say, "if there is a void outside the world, the world would be carried through it, since it has nothing that could contain and support it." We will say that it cannot be carried through the void. Since it inclines toward its own center. And it holds this as "down" where it inclines. If the world did not have the same center and "down," it could surely have been carried through the void, as will be demonstrated in the discourse on motion toward the center. And that also is said by the same people: if...