Proclus (412–485)

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Proclus was born in Constantinople into a Lycean family that was still faithful to the old Hellenic religion in a society already dominated by Christianity. The talented young man forsook a career as a lawyer and decided to devote his life entirely to philosophy. After studies in Alexandria, he arrived in 431 in Athens where he joined the Platonic school of Syrianus. After the death of his venerated master, he became the leader of this school and remained in that position for almost fifty years until his death in 485. As we know from his biographer Marinus, his whole life was devoted to teaching and writing. Proclus was also a deeply devout person. In the community of the school he continued to practice with his disciples the rituals of the old Hellenic religion as well as the theurgical rituals of the Chaldeans. For Proclus, Plato was more than a philosopher intent upon the search for the truth; he was also a divinely inspired prophet showing the soul a way of salvation. Reading Plato had become more than just a scholarly exerciseit was a religious activity of paramount importance.

Proclus was convinced that the truth had been revealed by the gods in many different ways, in obscure oracles, myths and symbols. He saw himself as the interpreter whose task it was to explain the hidden significance of those religious traditions in a civilization where they were doomed to disappear. It was his ambition to prove the harmony between Plato and the other sources of divinely inspired wisdom, in particular the Chaldean Oracles and the Orphic poems. In his view, only a philosophical approach could offer the framework and rational arguments needed for this interpretation. For that reason Plato remained for him the ultimate authority in all matters, divine and human. Aristotle, on the contrary, was given only a subsidiary role, as he never developed a proper theology. His significance was restricted to matters of logic and physics.

Proclus wrote commentaries on the dialogues of Plato that were part of the curriculum of the Neoplatonic school. The course started with the reading of the Alcibiades I about self-knowledge, which was regarded as an introduction to philosophy, and culminated in the explanation of the two major dialogues of the Platonic corpus: the Timaeus about the generation of the physical world and the Parmenides, which was thought to offer Plato's doctrine on the first principles. Proclus also wrote a series of interpretative essays on the Republic. The commentaries of Proclus are masterpieces of their genre: They not only offer a systematic interpretation of the text, but also introduce his own philosophical views and provide us with a wealth of information about the discussions within the Platonic tradition. That is particularly the case with the commentary on the Timaeus : Proclus defends Plato's explanation of the physical world as superior to that in Aristotle's Physics because only Plato discovered the ultimate (i.e., divine) causes of the physical phenomena.

Besides his work on Plato, Proclus composed a remarkable commentary on Euclid's Elements, the prologues of which offer a philosophical introduction to the study of the mathematical sciences. The Hypotyposis, or Outline of the Astronomical Hypotheses, is another indication of his interest in science and cosmology. Proclus also wrote short treatises on diverse subjects, such as the treatise On the Existence of Evils, in which he attempts to explain the existence of evil in a world proceeding from an absolutely good principle. If all agents act for some good and yet, evil occurs, it is unintended and uncaused. Evil cannot exist in its own right and no proper cause explains it. Its existence is parasitic (para-hypostasis ), supervening upon substances and acts. This doctrine, which was adopted by a Christian author writing under the pseudonym of Pseudo-Dionysus in his celebrated treatise On the Divine Names, became for centuries the dominant view in philosophical and theological debates on evil.

Besides his commentaries, Proclus owes his reputation to his two great syntheses of Platonic philosophy, the Elements of Theology and the Platonic Theology. Theology is for Proclus a rational investigation into the first causes and principles of all things. The first philosophers only admitted corporeal entities, such as fire or water, as first causes. Later philosophers recognized souls as principles of life and movement and thus discovered noncorporeal being. Aristotle posited unmoved intellects above the self-moving souls and considered the first intellect to be the ultimate divine cause. Only Plato, however, recognized a cause beyond intellect, beyond being, beyond knowledge and discourse, namely the One, from which all things including matter derive their existence (Platonic Theology I, 1). Therefore, Plato's theology is for Proclus (and for the entire Neoplatonic school since Plotinus) the accomplishment of all preceding theological speculation, since it reveals the "three principal hypostases": the One, the Intellect, the Soul.

Elements of Theology

In this work, the metaphysical counterpart of Euclid's Elements, Proclus demonstrates "in a geometrical manner" the most fundamental theorems of the theological or metaphysical science as he understands it. The work contains 211 propositions, each of them followed by a demonstration. The first part (props. 1112) examines the fundamental principles that govern the structure of all reality, such as the relation between the One and the many, the cause and the effect, the whole and the parts, transcendence and participation, procession and reversion, continuity and discontinuity, Being, Life and Intellect, limit and limitedness, self-movement and self-constitution, act and potency, eternity and time.

In the second part (props. 113211) Proclus gives a survey of all degrees of reality, applying to them the general metaphysical principles he had demonstrated before. He discusses successively the gods (or "henads"), the intellects and the souls. The physical realm falls outside the scope of this theological metaphysics. The Elements of Theology is without doubt the most original work of Proclus, not so much because of its content (which offers the standard doctrine of the Athenian school), but because of its extraordinary attempt to develop the entire Neoplatonic metaphysics from a set of axioms. It also had a tremendous influence, in particular through the Arabic adaptation that was made in the ninth century in the circle of Al-Kindī. In the middle of the twelfth century this Arabic treatise was translated into Latin. The Liber de Causis, as it was named, circulated as the work of Aristotle and thus obtained a great authority in medieval Scholasticism. The systematic character of the Elements and its rigorous method make it for the student the best introduction to the complicated thought of Proclus.

one and multiplicity

The Elements begin with the proposition that "every manifold in some way participates in unity." Without some form of unity a multitude would fall apart into an infinity of infinite things. A multitude cannot, however, be itself the unity it participates in. It is not the One, but a unified manifold, having unity as an attribute, and is therefore posterior to the One itself upon which it depends. All things, then, derive their being ultimately from the One from which they proceed.

This One must be identified with the Good, since it is the proper function of the One to hold together all things and maintain them in existence, which is also the function of the Good. For to hold a thing together and make it one is to give it its perfection and well-being, whereas dispersion is the cause of its destruction and evil. Since the Good is what unifies things and the One is what gives them perfection, the One and the Good are names designating the absolute principle from which and toward which all things eternally proceed and return.

Having demonstrated the necessity of the One as the first principle, Proclus explains how all things in all their specificity proceed from this One. It is impossible to admit that the utmost multiplicity of the material world with its particularized bodies would proceed immediately from the first principle. Plotinus had already argued that from the One comes first the Intellect and from the Intellect proceeds the Soul, which stands itself at the beginning of time, division, and movement. For Proclus, this Plotinian understanding of the procession is unsatisfactory, in particular with regard to the second level, the Intellect, which is identical with true Being and Life. If we respect the "law of continuity," which governs the procession of all things along the "chain of being," we cannot admit that the Intellect (which contains already the Forms of all things) comes into existence immediately after the absolute One. There must be "mean terms" connecting the extremities. From the One comes forth Being, from Being Life, from Life the Intellect. Whereas Being is the ultimate intelligible object (noēton ), the Intellect, which contains in its thought the paradigmatic Forms, is the properly intellectual level (noeron ). The intermediate realm of Life is the intelligible-intellectual. In this triad of hypostases, the superior level has the most comprehensive and farthest reaching causality: for all things participate in being, but not all are living or capable of thinking. The causality of the One reaches even further than that of Being, since matter, the indeterminate substrate of the physical realm, does depend on the One, though it does not really "exist."

the triadic dynamic structure of reality

Many propositions in the Elements concern causality (hence the Latin-Arabic adaptation is appropriately called De causis ): they are not about the physical causes, which are for Proclus only auxiliary causes, but about the "true causes," which always transcend their effect. Whatever produces something must be superior to the effect, which owes its existence to it. If this effect has itself the power to produce, it will produce again something inferior to it, until the procession comes down to what is altogether unproductive, that is, matter. Although the effect is inferior to its cause, it is also somehow similar to that which has produced it. The effect is in a secondary manner what its cause is primarily. Insofar as the effect is similar to its cause and shares its character, it is said to "remain" in its cause without yet having its proper existence. On the superior level, it exits "causally" or "potentially" (if "potency" is understood as a productive power).

A being only acquires its proper existence (hyparxis ) when it proceeds from its cause and becomes distinguished from it. Through the procession it becomes somehow dissimilar to the cause. Yet the procession from the cause cannot go on infinitely: the effect must also revert upon the cause from which it proceeds. Through this "return" (epistrophē ) the effect strives to be connected again with its cause and becomes similar to it. If things have their being through procession, they attain their well-being or perfection through reversion. For the cause of their well-being can only come from the origin of their being. The final cause is thus identical with the efficient, since all things desire as ultimate end that which is the principle of their procession. As Proclus formulates it: "All that is produced by a cause both remains in it and proceeds from it" (Elements of Theology, § 30). "All that proceeds from something reverts upon that from which it proceeds" (§ 31). Therefore, "all that proceeds from a principle and reverts upon it has a cyclical activity"(§ 33). All beings remain in their causes, proceed from them, and return to them, in an eternal circularity, since the end is identical with the origin. Proclus finds this triadic dynamic structure on all levels of reality.

participation and nonparticipation

When attempting to understand the relation between the Forms and the many things that are similar to them, Plato introduced the metaphor of "participation." Participation, however, raises as many problems as it solves, as Plato shows in the aporetic discussion of the Parmenides (which offered ammunition for Aristotle's subsequent criticism). The term seems to suggest that the many things sharing in the same Form take "parts" of it. How can one reconcile the transcendence of the Forms with their presence in the many things? If participation is real, the Forms must be immanent in the things sharing them and hence will be divided. But how, then, can the transcendence of the Forms be preserved? If, on the other hand, we stress the unity and the indivisibility of the Forms, we end up making participation impossible.

Proclus's solution to this problem is the distinction between the participated and unparticipated mode of a hypostasis. What is participated in by the particular things cannot be the ideal Form itself, but must be a form that comes forth from it and is present in them. These immanent forms are somehow comparable to the Aristotelian Forms in matter. However, whereas Aristotle rejects the transcendent Forms as an unnecessary duplication of reality, Proclus argues that the unparticipated Forms are necessary to guarantee the universal character of the forms in matter. The participated form belongs entirely to the particular thing sharing it. Since what inheres in one thing cannot be present in another, there is no explanation of the fact that the many things, though obtaining a proper form, have this form in common. By postulating an unparticipated Form, which exists prior to all participated forms proceeding from it, the Platonists can explain how the eidos is common to all that can share in it and nevertheless the same in all. As is said in proposition 23: "all that is unparticipated brings forth from itself the participated; and all the participated hypostases extend back to the unparticipated."

The distinction between the participated and the unparticipated not only applies to the Forms, but to all levels of reality: Soul, Intellect, and even the One. Within each realm a distinction must be made between the first unparticipated term (the "monad") and the "series" or multiplicity of beings of a similar nature coordinated with it. Thus, besides the many souls that are participated in on various levels by different bodiesthe particular souls by which each human being exists as a particular animal, the souls of demons, the planetary divine soulswe must postulate the existence of the unparticipated Soul, from which a multiplicity of souls proceeds according to diverse modes of participation.

Similarly, besides the many particular intellects participated in by different divine and human souls, there must also exist an absolute unparticipated Intellect, which comprises the totality of all Forms. The many intellects proceed from this absolute Intellect and form together with it a coordinate series of a similar intellectual nature. Following the same line of reasoning, we must also posit after the One, which is absolutely transcendent and can in no way be participated by the inferior levels, a manifold series of "ones," "units," or "henads" consequent upon the primal One, which are participated in by the different classes of being. Those henads are not the modalities of unity acquired by beings, but self-subsisting units which remain transcendent above the beings that depend upon them. Though they are in themselves beyond being and beyond knowledge, as is the primal One, in which they remain co-united, their distinctive properties can be inferred indirectly from the different classes of beings dependent upon them. "For differences within an order of participants are determined by the distinctive properties of the principles participated in" (Elements of Theology § 123).

In view of the different classes of beings depending upon them, we can distinguish, for example, intelligible, intellectual, hypercosmic, or encosmic henads. Yet, insofar as they are all self-subsisting units, they remain unified in the One itself. If the One stands for the first divine cause, the different henads constitute the different classes of the gods. "For every god except the One is participable" (§ 116). With this doctrine of the henads, Proclus can defendagainst Christian monotheismboth the unity and multiplicity of the divine. In his view, it is the main task of a Platonic philosopher to explain in a rational system the procession and the distinctive properties of all the classes of the gods we know through the diverse religious traditions. That is the purpose of Proclus's last magnum opus.

The Ppatonic Theology

Proclus distinguishes four types of theological discourse. Divinely inspired poets use dramatic stories (talking about sexual relations, births, fights, cuttings of organs) to symbolically indicate the processions of the divine principles and their mutual relations. This mythological discourse is characteristic of the ancient Hellenic theology, as known through the Orphic poems and the works of Homer and Hesiod. In oracular discourse (in particular the Chaldean Oracles ) prophets reveal the names and properties of the gods without resorting to the dramatic scenery of mythology. The Pythagoreans resort to mathematical analogies and similitudes (numbers, circles, spheres) to disclose the divine orders. Finally, there is scientific or dialectical theology, which investigates the divine classes and their properties using strictly rational arguments and an abstract philosophical vocabulary: one and many, being, whole and part, identity and otherness, similarity and dissimilarity.

This scientific theology has been brought to perfection by Plato in his dialogue Parmenides. In Proclus's interpretation, this dialogue displays the fundamental axioms and basic concepts needed for the development of a scientific theology. In the second part of this dialogue, Parmenides examines in a dialectical exercise the hypothesis of Unity, considering the consequences following from the position of the One and from its denial, both for the One and for what is other than the One. If we start from the hypothesis of the One, only negative conclusions seem to follow: the One has no parts and is not a whole; it is not in something nor in itself; it is neither similar nor dissimilar. One cannot even say that it "is" or "is one." In short, no names, no discourse, no knowledge of it is possible. Parmenides therefore has to restate his original hypothesis, now emphasizing the existence of the One. All attributes that were denied in the first hypothesis can be predicated of this One-that-is.

The interpretation of the different hypotheses of the Parmenides (of which we mention only the first two) led to a lively debate in the Neoplatonic school, as we know from Proclus's commentary. Proclus defends a theological interpretation of this dialectical discussion about the One and the Many. If the "One" stands for the first principle, the successive hypotheses of the Parmenides must refer to the different principles of the whole of reality. The One of the first hypothesis, of which no discourse is possible, is the absolute, unparticipated One or primal god. In the second hypothesis, Parmenides deduces, through the subsequent conclusions following from the position of the One-that-is, the different modes of unity ("henads") that are participated in by the different degrees of being. Whereas the first hypothesis leads to a negative theology, the deductions from the second hypothesis give the articulations of a positive theology. "In this dialogue proceed all the divine classes in good order from the first cause and demonstrate their mutual connection" (Platonic Theology, I, ch. 7).

When interpreted in this way, the Parmenides provides a framework in which the other discourses about the gods can be integrated and decoded: the mythological stories about Zeus and Kronos from the Hellenic and Orphic traditions, the strange divine names revealed in the Chaldean Oracles, the mathematical theologumena of the Pythagoreans, the various scattered remarks about the gods in the other dialogues of Plato. In the Renaissance, Marsilio Ficino adapted the model of Proclus's theology in an original way to integrate the revealed truth of Christianity.


It is difficult to evaluate the originality of a thinker who, in most of his works, claims to be nothing but a faithful follower of his master Syrianus. It is Proclus, however, who put his mark on the development of the later tradition of Neoplatonism in Byzantine, Arabic, and Latin medieval thought. His huge influencemuch greater than that of Plotinusis to be explained mainly by two important indirect channels: the Christian reception of his theology by Pseudo-Dionysus and the Arabic adaptation of the Elements in the Liber de Causis. And yet it is no historical accident that Proclus gained this fame. The diadochos (or successor) of Plato, as he was named, has been the authoritative commentator of Plato and the great systematizer of Neoplatonic metaphysics.

See also Liber de Causis; Neoplatonism; Plato; Plotinus; Pseudo-Dionysus.


the life of proclus

Marinus, Vie de Proclus. Edited and translated by Henri Saffrey and Alain Segonds. Paris: Les Belles Lettres, 2003.

annotated editions and translations

The Elements of Theology. 2nd ed. Edited and translated by E. R. Dodds. Oxford: Clarendon Press, 1992.

A Commentary on the First Book of Euclid's Elements. Translated by Glenn Morrow. Princeton, NJ: Princeton University Press, 1970.

Proclus' Commentary on Plato's Parmenides. Translated by Glenn Morrow and John M. Dillon. Princeton, NJ: Princeton University Press, 1987.

Commentaire sur le Timée. 5 vols. Translated by A. J. Festugière. Paris : Vrin, 19661968.

Commentaire sur la République. 3 vols. Translated by A. J. Festugière. Paris: Vrin, 1970.

Théologie platonicienne. 6 vols. Edited and translated and edited by Henri Saffrey and Leendert Westerink. Paris: Les Belles Lettres, 19681997.

Commentaire sur le Premier Alcibiade. 2 vols. Edited and translated by Alain Segonds. Paris: Les Belles Lettres, 1986. English translation by W. O'Neill (2nd ed., The Hague: Nijhoff, 1971).

Commentaire sur le Parménide. Vol. 1. Edited and translated by Alain Segonds and Carlos Steel. Paris: Les Belles Lettres, 2005.

On the Existence of Evils. Translated by Jan Opsomer and Carlos Steel. London: Duckworth, 2003.

Proclus' Hymns. Translated and annotated by R. M. Van den Berg. Leiden, Boston, Köln: Brill, 2001.


Steel, Carlos, ed. Proclus: Fifteen Years of Research: A Critical Bibliography (19902004). Lustrum 44 (2005).

For a complete survey of editions and translations, see Plato Transformed. Leuven: De Wulf-Mansion Centre, Katholieke Universiteit Leuven.

secondary literature

Siorvanes, Lucas. Proclus. Neo-Platonic Philosophy and Science. New Haven and London: Yale University Press, 1996.

Segonds, Alain, and Carlos Steel, eds. Proclus et la théologie platonicienne. Leuven-Paris: Leuven University PressLes Belles Lettres, 2000.

Carlos Steel (2005)