One of the points that Lovejoy makes in the book of that title I mentioned last week is the importance, in the Neo-Platonist conceptions and in the later development of the "chain of being" metaphor, of what he calls the principle of plenitude. This is the underlying notion that everything that can exist must exist, that creation would not be possible at all were it to leave gaps. The value of this idea for a certain type of theodicy is clear enough. This caused theological difficulties when these ideas were absorbed into Christianity. I'll quote a bit of what Lovejoy has to say about those difficulties: "For that conception, when taken over into Christianity, had to be accommodated to very different principles, drawn from other sources, which forbade its literal interpretation; to carry it through to what seemed to be its necessary implications was to be sure of falling into one theological pitfall or another." The big pitfalls were: determinism on t...