15. 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.