,

But Empedocles's opinion is, that the world is one; yet by no means the system of this world must be styled the universe, but that it is a small part of it, and the remainder is inactive matter.

What to Plato seems the truest he thus declares, that there is one world, and that world is the universe; and this he endeavors to evince by three arguments. First, that the world could not be complete and perfect, if it did not within itself include all beings. Secondly, nor could it give the true resemblance of its original and exemplar, if it were not the one only begotten thing. Thirdly, it could not be incorruptible, if there were any being out of its compass to whose power it might be obnoxious. But to Plato it may be thus returned. First, that the world is not complete and perfect, nor doth it contain all things within itself. And if man is a perfect being, yet he doth not encompass all things. Secondly, that there are many exemplars and originals of statues, houses, and pictures. Thirdly, how is the world perfect, if anything beyond it is possible to be moved about it? But the world is not incorruptible, nor can it be so conceived, because it had an original. To Metrodorus it seems absurd, that in a large field one only stalk should grow, and in an infinite space one only world exist; and that this universe is infinite is manifest by this, that there is an infinity of causes. Now if this world be finite and the causes producing it infinite, it follows that the worlds likewise be infinite; for where all causes concur, there the effects also must appear, let the causes be what they will, either atoms or elements.