 Before looking at the way he attempts to advance moral philosophy and the theory of the good, it will help to have some background concerning what Leibniz calls the metaphysical good and its correlative metaphysical evil. In uniting goodness with reality, Leibniz borrows, not without putting his own stamp on it, a view that had currency with certain medieval philosophers (e.g., Augustine, Boethius, and Aquinas). The doctrine nonetheless originated in the Neoplatonic philosophy of Plotinus (204–269) and Porphyry (234–c.305), though there is clearly suggestion of it in Plato (e.g., Republic 518c, Timaeus 28b). In reuniting goodness and reality, or to what he interchangeably refers to as perfection, Leibniz thus characteristically recovers and attempts to restore a doctrine that had currency among medieval thinkers (for a study of the medieval treatment of the doctrine of metaphysical goodness, see the essays in MacDonald (ed.) 1991).