Plotinus maintains that there is a single first principle, the One (or the Good), from which all other things derive. He is usually thought to hold this view on the grounds that any other thing’s existence depends on its participation in a paradigm of unity. This paper argues that Plotinus has a further, independent argument for adopting a single first principle, according to which principle pluralism is committed (unacceptably) to attributing good cosmic states of affairs to chance. This argument exhibits (...) similarities to ancient design arguments, but is used to draw the more radical conclusion that there is only one non-derivative existent. (shrink)