Book I of Meteora

...bounded. For example, immediately in the universe, the air is bounded, and it ends in something of a different kind, such as ether and water. And likewise, the ether [ends in air and heaven, and the heaven in ether] and the void. And water ends in earth and air. And earth ends in water and air. And likewise, our bodies end in something of a different kind, namely the surface, which is not a body. It is therefore necessary that even if the void surrounding the world is bounded, and is not infinite, it must end in something of a different kind. But it is not possible to conceive of anything of a different kind from the void in which it might end. Therefore, it is infinite. For even if we should conceive of something of a different kind from the void in which it would be bounded, this would also need to be filled, and that which has filled it would become a body. And thus it would be necessary for there to be a body outside the world. Which the physicus physical argument does not dictate, since all bodies are contained by the world. From which it is known that it is not possible for the void outside to be bounded. Therefore, it is infinite. Moreover, just as everything that is bounded is understood to be contained by something (otherwise, it would not even be bounded), so too if the void is bounded, it is necessary for it to be contained by something. What, then, would this be? A body? Impossible, since there is no body outside the world. And if...

...which it is bounded, and which is different from the bounded thing itself: just as immediately in the universe of things, the bounded air is defined in something else of a different kind, and is finished by fire and water: and fire also, by air and heaven: and heaven likewise, by fire and the void: and water equally, by air and earth: and finally, earth, by water and air. Similarly, our bodies are bounded by something of a different kind, namely by a surface, which is not a body. It is necessary, therefore, if the void that embraces the world is bounded, and is not infinite, that it should end in something else of a different kind. But one cannot think of anything of a different kind from the void into which it might end. Therefore, it is infinite. For if we had conceived of something of a different kind from the void by which it might be bounded, it would be necessary for this to be filled, and that by which it is filled would be a body. And so it would be necessary for there to be a body outside the world, which physical reason does not admit, since all bodies are contained by the embrace of the world. From which it becomes manifest that the void which is outside cannot be bounded. Therefore, it is infinite. Furthermore, just as everything that is bounded is understood to be contained by something (if not, it would not even be bounded), so too if the void is bounded, it is necessary that it be contained by something. What, then, will that be? A body? It cannot be. Since there is no body outside the world. And if...