Whatever their differences, the demiurge in Plato's Timaeus and the Prime Mover in Aristotle's Metaphysics have this much in common: both are finite beings whose purpose is to explain a feature of the world, not everything about it. The Demiurge imposes order on a preexistent chaos that he has not created and over which he has only limited control. The Prime Mover is the last in a series of causes needed to explain the eternal motion of the heavens but does nothing to explain why they are there in the first place.

It is clear that this picture of the world is subject to a serious objection: How can we understand something whose existence is ungenerated? After all, ungenerated is another name for unexplained. Plotinus' great achievement is that he gives us a higher level of abstraction. No longer is the question how to explain this or that feature but how to explain the world as a whole. According to what may be his best-known insight, it is impossible to understand anything unless we view it as one of something. Thus, everything that is, insofar as it is, owes its existence to the first principle, or as Plotinus calls it, the One. The first principle is the common source (archē) of all things because everything is derived from it and nothing can exist without it. Insofar as it is the source of existence, it is also the source of value.