Proclus, the Neoplatonist, called the SUCCESSOR (Diadochos), i.e. of Syrianus, as the head of the Athenian school, was born in Constantinople about 411 A.D. He was of Lycian origin, and received his first instruction at Xanthus, in Lycia. He then studied at Alexandria under Arion, Leonaras, Hero, and especially under Heliodorus, with whom he applied himself chiefly to Aristotelian and Platonic philosophy. From thence he went to Athens, where a certain Plutarch, a philosopher, and his daughter, Asclepigeneia, a priestess of Eleusis, became his instructors, chiefly in theurgic mysteries. The vivid imagination and enthusiastic temperament which in his childhood already had led him to believe in apparitions of Minerva and Apollo, naturally convinced him, when all the influences of the mysteries were brought to bear upon him, still more of his immediate and direct intercommunication with the gods; and he came to distinctly believe himself one of the few chosen links of the Hermaic chain through which divine revelation reaches mankind. His soul had, he thought, once lived in Nicomachus the Pythagorean, and, like him, he had the power to command the elements to a certain extent, to produce rain, and to temper the sun's heat. The Orphic Poems, the writings of Hermes, and all the mystical literature of that occult age were to him the only source of true philosophy, and he considered them all more or less in the light of divine revelations. That same cosmopolitan spirit in religious matters which pervaded Rome towards her end had spread throughout all the civilised pagan world of those days, and Proclus distinctly laid it down as an axiom that a true philosopher must also be a hierophant of the whole world. Acquainted with all the creeds and rites of the ancient Pantheons of the different nations, he not only philosophised upon them in an allegorising and symbolising spirit, as many of his contemporaries did, but practised all the ceremonies, however hard and painful. More especially was this the case in the severity of his fasting in honour of Egyptian deities—a practice, which, if it fitted him more and more for his hallucinations and dreams of divine intercourse, on the other hand more than once endangered his life. Of an impulsive piety, and eager to win disciples from Christianity itself, he made himself obnoxious to the Christian authorities in Athens, who, in accordance with the spirit of religious intolerance and fanaticism which then began to animate the new and successful religion against which Proclus waged constant war, banished him from this city. Allowed to return, he acted with somewhat more prudence and circumspection, and only allowed his most approved disciples to take part in the nightly assemblies in which he propounded his doctrines. He died in 485, in his full vigour, and in the entire possession of all those mental powers, for which he was no less remarkable than for his personal beauty and strength.
As to his system, some modern philosophers have exalted it to an extent which his own writings scarcely warrant. Victor Cousin holds that he has concentrated in it all the philosophical rays which emanated from the heads of the greatest thinkers of Greece, such as Pythagoras, Plato, and Aristotle. The predominant law of development is triadic in character. The existence of what is produced in that which produces it, its emergence from it, and its return to it (μονή, πρόοδος, επιστροφή) are the three moments, by the continued repetition of which the totality of things is developed from their origin. The final source of this development is the original essence, elevated above all being and knowledge, between which and the intelligible there intervenes an intermediary member—the absolute unities (αὐτοτελεῖς ἐνάδες), together forming the single supernal number. Next to this comes the three spheres of the intelligible, the intellectual-intelligible (νοητὸν ἅμα καὶ νοερὸν), and the intellectual. The chief property of the first is being; of the second, life; of the third, thought. Of these spheres the first two are again divided into three triads each, and the triad again into hebdomads, each separate member regarded as a divinity. The soul is made of three kinds of parts—divine, demonic, and human. Of these the divine fall into three orders: the four triads of hegemonic gods, an equal number of gods free from the world (ἀπὸλυτοι), and the gods within the world, who are divided into star-gods and elementary gods. The demons are divided into angels, demons proper, and heroes. The soul enters temporarily into the material body, but it does not create matter, which comes directly from the unlimited—with the limited and the mixed, the components of the first intelligible triads. Space he considers as a body consisting of the finest light, which body penetrates that of the world. He distinguishes the principle of unity or divinity in the soul from thought or reason. It is capable by divine illumination of mystic union with the Deity. Indeed, faith alone is essential to the attainment of Theurgy, which, comprising mantie and supernatural inspiration, is preferable to all human wisdom; and in this Proclus chiefly differs from Plotinus, with whose system he agrees in most other respects.
There is no edition of the complete works of Proclus, but that of Victor Cousin (6 vols. 8vo. Paris, 1820) contains the Commentaries on the First Alcibiades and the Carmenides, and the treatises De Libertate, Providentia, et Molo (in a Latin translation); his second edition (1 vol. 4to, 1864) contains in addition to these the Hymns. Thomas Taylor, 'the Platonist,' published in 1788-89 translations of the Commentary on Euclid, with the Life by Marinus; the Six Books on the Theology of Plato in 1816; the Commentaries on the Timæus in 1820; the Fragments on the Lost Writings in 1825; On Providence, and On Evil, in 1833. The Commentaries in Platonis Timæum (ed. by Schneider, Breslau, 1847) was the one among his treatises that Proclus esteemed most highly. See Zeller's Philos. der Griechen (3d ed., 1881, iii. 2), and other books named under NEOPLATONISM.