If souls continue to exist, how does the air contain them from eternity?- But how does the earth contain the bodies of those who have been buried from time so remote? For as here the mutation of these bodies after a certain continuance, whatever it may be, and their dissolution make room for other dead bodies; so the souls which are removed into the air after subsisting for some time are transmuted and diffused, and assume a fiery nature by being received into the seminal intelligence of the universe, and in this way make room for the fresh souls which come to dwell there. And this is the answer which a man might give on the hypothesis of souls continuing to exist. But we must not only think of the number of bodies which are thus buried, but also of the number of animals which are daily eaten by us and the other animals. For what a number is consumed, and thus in a manner buried in the bodies of those who feed on them! And nevertheless this earth receives them by reason of the changes of these bodies into blood, and the transformations into the aerial or the fiery element.
Some things are hurrying into existence, and others are hurrying out of it; and of that which is coming into existence part is already extinguished. Motions and changes are continually renewing the world, just as the uninterrupted course of time is always renewing the infinite duration of ages. In this flowing stream then, on which there is no abiding, what is there of the things which hurry by on which a man would set a high price? It would be just as if a man should fall in love with one of the sparrows which fly by, but it has already passed out of sight. Something of this kind is the very life of every man, like the exhalation of the blood and the respiration of the air. For such as it is to have once drawn in the air and to have given it back, which we do every moment, just the same is it with the whole respiratory power, which thou didst receive at thy birth yesterday and the day before, to give it back to the element from which thou didst first draw it.
Consider how many things in the same indivisible time take place in each of us, things which concern the body and things which concern the soul: and so thou wilt not wonder if many more things, or rather all things which come into existence in that which is the one and all, which we call Cosmos, exist in it at the same time.
He who does not know what the world is, does not know where he is. And he who does not know for what purpose the world exists, does not know who he is, nor what the world is. But he who has failed in any one of these things could not even say for what purpose he exists himself. What then dost thou think of him who avoids or seeks the praise of those who applaud, of men who know not either where they are or who they are?
Men exist for the sake of one another. Teach them then or bear with them.