By any standard of intellectual prowess, Plotinus is one of the intellectual giants of antiquity, on a par with the likes of Plato, Aristotle, and Chrysippus, even if modernity is still hesitant to accord him such an exalted status. As in the case of his preeminent precursors, Plotinus’ philosophical system combines innovation with tradition. The question of precisely which predecessors inspired him is still unclear and in need of further investigation. Carefully selected passages from Plato’s dialogues and Aristotle’s Metaphysics often serve him as starting points for his own speculations; Stoic ethics is very much in evidence, as are the views of the Peripatetic philosopher Alexander of Aphrodisias (2nd-3rd centuries). A general intellectual background is provided by the so-called Middle Platonists, above all Numenius of Apamea (2nd century). Moreover, it is not impossible that Gnosticism (which Plotinus vehemently opposed) as well as the writings circulating under the name of Hermes Trismegistus confirmed or even informed his metaphysical monism. Lastly, Plotinus may have been well aware of the rise of Christianity, but if so, he was not as alarmed by it as his pupil Porphyry.