"The quantity of fire in a flame... appears to remain the same, the flame seems to be... a "thing"... yet the substance... is continually changing. ...[P]assing away in smoke ...its place ...always being taken by fresh ...fuel that feeds it. ...If we regard the world as an "ever-living fire" (fr. 20), we can understand ...it ...always becoming all things, while all things are always returning to it."