A powerful but difficult tradition in philosophy and theology associates reality, perfection, absence of change or eternity, and self-sufficiency. A perfect being would be that which is most real; there is a departure from perfection if anything that could be real is not. Hence a perfect being has no potential that is unrealized, and undergoes no change. Evil is downgraded to mere defect, or absence or lack of something positive: criminality is the failure of some genuine potentiality to be actual, and all such actualization is good. The line of thought is at least as old as Parmenides and the Eleatics. It issues in the association of perfection with self-sufficiency, since the real cannot depend upon the less real. The results are visible in the ethics of Plato and Aristotle, and are crucial in creating the climate of thought for the ontological, cosmological, and degrees of perfection arguments for the existence of God. See also chain of being; plenitude, principle of.