<philosophical terminology> belief that everything that can be, is. Leibniz clearly maintained that every genuine possibility must be actualized in the best of all possible worlds, and A. O. Lovejoy supposed adherence to this notion a significant source for the notion of the great chain of being envisioned by such philosophers as Plato, Plotinus, and the Neoplatonics. Recommended Reading: Arthur Oncken Lovejoy, The Great Chain of Being: A Study of the History of an Idea (Harvard, 1970).
[A Dictionary of Philosophical Terms and Names]
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