It is plain that St. Augustine, in his first Christian period, was deeply indebted to Plotinus, whom he knew through Victorinus and frequently quotes by name; calling him “one of those more excellent philosophers” whose doctrine of the soul is in harmony with the Prologue of the Fourth Gospel. When he came to write the “Confessions,” the glamour of the Platonic vision had begun to fade, and he was able to deal in a critical spirit with his own brief Plotinian experience of “that which Is” (VII. 17). Nevertheless, none can understand that book without some knowledge of the Enneads, from which all its finest passages are derived, and in more than one instance—especially Book VII and the celebrated tenth chapter of Book IX—closely imitated. In Augustine’s invocation of “the Beauty so old and so new,” in his description of the “Country which is no vision but a Father-land,” or of “the Light which never changes, above the soul, above the intelligence,” we see how closely he had studied them, the extent to which their language had permeated his thought. It is, however, in the tracts composed soon after his conversion—e.g. De Quantitate Animæ, written about A.D. 388—that their influence is most strongly marked; and the ecstatic vision of the One is definitely put forward as the summit of Christian experience. From this time onwards, the main outlines of mystical theology were more or less fixed: and since St. Augustine was one of the most widely read and deeply reverenced of the Fathers, with an authority hardly inferior to that of Scripture itself, its Neoplatonic colour was never lost. Wherever Christian mysticism passes from the emotional and empirical to the philosophic, this colour is clearly seen, and the concepts of Plotinus, more or less disguised, reappear: even in those mediæval writers who had no direct acquaintance with Greek philosophy. The immense popularity of the so-called Dionysian writings, which derive much of their doctrine through Proclus from the Enneads, helped to establish yet more firmly the Neoplatonic character of Christian and also of Sūfi mysticism. Through these writings the conceptions of the Super-essential Godhead; of successive spiritual spheres or emanations of descending splendour, intervening between the Absolute and the physical world; and of ecstatic union with the transcendent and unconditioned One as the term of religious experience, passed over from the ancient to the mediæval world. Translated from Greek into Syriac in the fifth century, they deeply affected Sūfi philosophy. They entered Western thought in the ninth century, through Erigena’s Latin translation. It is said that by A.D. 850 Dionysius was known from the Tigris to the Atlantic: and from this time onwards his influence, and through him that of Plotinus, can be traced in the spiritual literature of Christianity and Islam.
Erigena, whose original works are strongly coloured by Neoplatonism, is the first mediæval writer in whom this influence appears. He follows Plotinus and Dionysius closely in teaching that the Absolute Godhead is “beyond being” and therefore transcendent to the trinity of Persons; a doctrine of doubtful orthodoxy, which was of great importance in the later development of mysticism. But a still closer approximation to the thought, and especially to the psychology of Plotinus, is found in Richard of St. Victor: perhaps the greatest mystical theologian, certainly one of the most influential writers, of the early Middle Ages. In the thirteenth and fourteenth centuries his works, which are now hardly read, circulated through western Europe, and shaped the developing mysticism of England, Germany, and Flanders. Dante, who calls him one “who in contemplation was more than man,” places his radiant soul among those of the great teachers in the Heaven of the Sun (Par. X. 131). Abandoning alike the many worlds of Dionysius and the crude dualism of popular religion, Richard taught that three spheres are open to human contemplation: sensibilia, intelligibilia, and intellectibilia—a series closely analogous to the three worlds of Plotinus. He said that three kinds of contemplation on man’s part corresponded with these worlds. These are mentis dilatatio, a widening of the soul’s vision, which yet remains within the natural order: mentis sublevatio, an uplifting of the illuminated mind to the apprehension of “things above itself” (or, as Neoplatonists would say, intelligibles); and finally mentis alienatio or ecstasy, in which the soul gazes on Truth in its naked simplicity. Then “elevated above itself and rapt in ecstasy, it beholds things in the Divine Light at which all human reason succumbs.” This divine light is the lumen gloriæ, the radiance of the spiritual or intelligible world, which transforms the soul and makes it capable of beholding God; a conception which became a commonplace of mediæval theology, was adopted by nearly all the mystics, and plays an important part in the Paradiso.
“Lume è lassù, che visibile face
lo Creatore a quella creatura
che solo in lui vedere ha la sua pace” (xxx. 100).
Ruysbroeck—a student of Dionysius and of Richard—says of it in The Twelve Béguines: “From the Face of the Father there shines a clear light on those souls whose thought is bare and stripped of images, uplifted above the senses and above similitudes, beyond and without reason, in high purity of spirit. This Light is not God, but it is the mediator between the seeing thought and God.” These passages and many like them can be shown to derive directly through St. Augustine from the Enneads. Thus Plotinus says: “Light is visible by Light. The Nous sees itself, and this light, shining on the soul, enlightens it and makes it a member of the spiritual world” (V. 3. 8). Augustine, apparently referring to this passage among others, says: “Often and in many places does Plotinus declare, expounding the meaning of Plato, that what they believe to be the Soul of the World has its bliss from the same source as ours, namely, a Light which it is not, but by which it was created, and from whose spiritual illumination it shines spiritually” (De Civ. Dei. X. 2). And, of his own ecstatic experience, “I entered and beheld with the mysterious eye of my soul the Light that never changes, above the eye of my soul, above my intelligence.... He who knows the truth knows that Light, and he who knows that Light knows Eternity” (Conf. VII. 10).
From the thirteenth century onwards, the majority of the mediæval mystics show knowledge and appreciation of those Plotinian ideas which reached them—though in an attenuated form—through St. Augustine, Dionysius, and Richard of St. Victor. Even the Franciscan and Christo-centric enthusiasm of such contemplatives as Jacopone da Todi and Angela of Foligno was affected by these lofty conceptions. Thus Jacopone takes from the Neoplatonists the three stages of spiritual experience, and describes in unequivocal language his successive achievements of that Logos-Christ—so near the Plotinian Nous—“che de omne bellezze se’ fattore,” and of the “Imageless Good” who cannot be named. So too, Angela’s successive visions of the divine fullness and beauty, and of “the ineffable Thing of which nought may be said” depend for their expression on the same philosophy.
Nor was its penetrative influence confined to the mystical schools. St. Thomas Aquinas, who accepts and expounds in the Summa (I. q.12. a.5) the doctrine of the lumen gloriæ, is considerably indebted to Plotinus in several other particulars; though he cites him inaccurately, and does not seem to have known him at first hand. In a remarkable passage, which afterwards influenced one of the finest rhapsodies of Ruysbroeck, he has actually “lifted” the most celebrated phrase in the Sixth Ennead, and adapted it to the distinctively Christian and non-Platonic view of divine union, as a “mutual act” of God and the soul. “In a wonderful and unspeakable manner,” says St. Thomas of the soul in this place, “she both seizes and is seized upon, devours and is herself devoured, embraces and is violently embraced; and by the knot of love she unites herself with God, and is with Him as the Alone with the Alone.”
It is in a later and less orthodox son of St. Dominic, the formidable and adventurous thinker Eckhart, that the influence of Plotinus on the mediæval mind is best seen: passing through him to Suso, Tauler, Ruysbroeck, and other mystics of the fourteenth century. Eckhart’s philosophy still provides one of the most suggestive glosses upon the Enneads. He made that distinction between the absolute and supra-personal Godhead and the God of devotion, which was almost inevitable for a Christian thinker trying to find a place in theology for the Neoplatonic One. The Godhead, he says, is “a non-God, a non-Spirit, a non-person, a non-image: a sheer pure One.” The Son, in whom “the Father becomes conscious of Himself,” combines the attributes of the Logos-Christ with those of the Nous. In Him are the archetypes of all created things. There is thus an emanation from the Godhead, through the Son, into creation. The soul’s destiny is exactly that conceived by Plotinus: it must ascend to the spiritual world, and through it to its origin, the One, “flowing back into the bottom of the bottomless fountain from which it flowed forth.” In Tauler and Suso, and especially in the great Flemish contemplative Ruysbroeck, these ideas—though modified by their inferior speculative ability and more ardent spirit of Christian devotion—are still strongly felt: and since their works and those of their disciples nourished many succeeding generations of contemplatives, through them the mystical side of the Neoplatonic tradition was handed down. In Ruysbroeck, with his threefold division of spiritual experience into “the moral life, the contemplative life, and the super-essential life,” and his astonishing and detailed descriptions of the soul’s achievement of the Essential Unity, the “death into the One through love,” the vision of Plotinus is fully baptized into the Catholic Church. In Jacob Boehme, who drew through Schwenkenfeld and Weigel from Eckhart and his school, the doctrine of the three worlds which forms the basis of his cosmology contains distinct reminiscences of the Plotinian Triad. “These three,” he says, “are nought else than the One God in His wonderful works ... and we are thus to understand a threefold Being, or three worlds in one another.” His conception of the Light-world, source of all spiritual beauty and home of “the true human essence,” is very near to the Nous. Yet the very closeness with which all these mystics follow those parts of the Neoplatonic doctrine which appeal to them, makes it possible for us to measure the distance which separates their minds, their tone and temper, from that of Plotinus and his school. The calm, the austerity of thought, the emphasis on beauty, the clear cool light of the Intelligible World have departed. These men see philosophy through the haze of Christian feeling. Their work is full of passionate effort; is centred on the ideas of sacrifice and of pain. Their religion is coloured by the sharp Christian consciousness of sin, and by the difficulty—never squarely faced—of reconciling devotion to a personal redeemer with the mystical passion for the Absolute. That the philosophy of the Enneads was able to enter a world so remote from its spirit, and come to terms with an attitude of mind in many respects opposed to that of its creator, is an oblique proof of the authenticity of its claim to interpret the spiritual experiences of man.