And if the world also is destroyed, then it must of necessity be so either by some external cause, or else by some one of the powers which exist within itself; and both these alternatives are impossible, for there is nothing whatever outside of the world, since all things are brought together in order to make it complete and full, for it is in this way that it will be one, and whole, and free from old age; it will be one, because if anything were left outside of it, then another world might be created resembling that which exists now; and whole, because the whole of its essence is expended on itself; and exempt from old age and from all disease, since those bodies which are liable to be destroyed by disease or old age are violently overthrown by external causes, such as heat, and cold, and other contrary qualities, no power of which is able to escape so as to surround and attack the world, all those being entirely enclosed within, without any part whatever being separated from the rest.
But if indeed there is any external thing it must by all means be a vacuum, or else a nature absolutely impossible, which it would be impossible should either suffer or do anything. And again, it will also not be dissolved by any cause existing within itself; first of all because, if it were, then the part would be greater and more powerful than the
 
whole, which is the greatest possible absurdity, for the world, enjoying an unsurpassable power, influences all its parts, and is not itself influenced or moved by any one of them; in the second place because, since there are two causes of corruption, the one being internal and the other external, those things which are competent to admit the one must also by all means be liable to the other; and a proof of this may be found in oxen, and horses, and men, and other animals of similar kinds, because it is their nature to be destroyed by the sword, or to be liable to die by disease; for it is difficult, or I might rather say impossible, to find anything which, being by nature at the mercy of some external cause perceptible by the intellect, will still not be liable to corruption ... by itself when the world was not.

 Since, therefore, the arrangement of the world is such as I have endeavoured to describe it, so that there is no part whatever left out, so as for any force to be applied, it has now been proved that the world will not be destroyed by any external thing, because in fact nothing whatever external has been left at all; nor will it be destroyed by anything in itself on account of the proof which has already been considered and stated, according to which that which was obnoxious to the power of one of those causes was also naturally susceptible of the influence of the other.
 And there are testimonies also in the Timaeus to the fact of the world being exempt from disease and not liable to destruction, such as these: "Accordingly, of the four elements the constitution of the world receives each in all its integrity; for he who compounded it made it to consist of the whole of fire, and the whole of water, and the whole of air, and the whole of earth, not leaving any portion or any power of any one of them outside, from the following intentions:—