Men who give up the common goal of all things that exist, thereby cease to exist themselves. Some may perhaps think it strange that we say that wicked men, who form the majority of men, do not exist; but that is how it is. I am not trying to deny the wickedness of the wicked; what I do deny is that their existence is absolute and complete existence. Just as you might call a corpse a dead man, but couldn't simply call it a man ... A thing exists when it keeps its proper place and preserves its own nature. Anything which departs from this ceases to exist, because its existence depends on the preservation of its nature.

boethius, consolation of philosophy, IV.ii, p.91