Proclus Lycius
The beginning of the first Latin edition of Proclus' Commentary on Euclid's Elements
Born	412 Constantinople, Thracia, Eastern Roman Empire
Died	485 (aged 72–73) Athens, Achaea, Eastern Roman Empire
Other names	"The Successor"
Era	Ancient philosophy
Region	Western philosophy
School	Neoplatonism
Main interests	Metaphysics
Notable ideas	Platonic theology

Proclus Lycius (/ˈprɒkləs laɪˈsiəs/; 8 February 412 – 17 April 485), called Proclus the Successor (‹See Tfd›Greek: Πρόκλος ὁ Διάδοχος, Próklos ho Diádokhos), was a Greek Neoplatonist philosopher, one of the last major classical philosophers of late antiquity. He set forth one of the most elaborate and fully developed systems of Neoplatonism and, through later interpreters and translators, exerted an influence on Byzantine philosophy, Early Islamic philosophy, Scholastic philosophy, and German Idealism, especially G.W.F. Hegel, who called Proclus's Platonic Theology "the true turning point or transition from ancient to modern times, from ancient philosophy to Christianity."^[1]

The primary source for the life of Proclus is the eulogy Proclus, or On Happiness that was written for him upon his death by his successor, Marinus,^[2] Marinus' biography set out to prove that Proclus reached the peak of virtue and attained eudaimonia.^[2] There are also a few details about the time in which he lived in the similarly structured Life of Isidore written by the philosopher Damascius in the following century.^[2]

According to Marinus,^[3] Proclus was born in 412 AD in Constantinople to a family of high social status from Lycia, and raised in Xanthus. He studied rhetoric, philosophy and mathematics in Alexandria, with the intent of pursuing a judicial position like his father. Before completing his studies, he returned to Constantinople when his rector, his principal instructor (one Leonas), had business there.^[4] Proclus became a successful practicing lawyer. However, the experience of the practice of law made Proclus realize that he truly preferred philosophy. He returned to Alexandria, and began determinedly studying the works of Aristotle under Olympiodorus the Elder. He also began studying mathematics during this period as well with a teacher named Heron (no relation to Hero of Alexandria, who was also known as Heron). As a gifted student, he eventually became dissatisfied with the level of philosophical instruction available in Alexandria, and went to Athens, philosophical center of the day, in 431 to study at the Neoplatonic successor of the New Academy, where he was taught by Plutarch of Athens (not to be confused with Plutarch of Chaeronea), Syrianus, and Asclepigenia; he succeeded Syrianus as head of the Academy in 437, and would in turn be succeeded on his death by Marinus of Neapolis. He lived in Athens as a vegetarian bachelor, prosperous and generous to his friends, until the end of his life, except for a one-year exile, to avoid pressure from Christian authorities.^[2] Marinus reports that he was writing seven hundred lines each day.

One challenge with determining Proclus' specific doctrines is that the Neoplatonists of his time did not consider themselves innovators; they believed themselves to be the transmitters of the correct interpretations of Plato himself.^[5] Although the neoplatonic doctrines are much different from the doctrines in Plato's dialogues, it's often difficult to distinguish between different Neoplatonic thinkers and determine what is original to each one.^[5] For Proclus, this is largely only possible with Plotinus, the only other Neoplatonic writer for whom a significant amount of writings survive.^[5]

Proclus, like Plotinus and many of the other Neoplatonists, agreed on the three hypostases of Neoplatonism: The One (hen), The Intellect (nous) and The Soul (psyche), and wrote a commentary on the Enneads, of which unfortunately only fragments survive. At other times he criticizes Plotinus' views, such as the prime mover.^[5] Unlike Plotinus, Proclus also did not hold that matter was evil, an idea that caused contradictions in the system of Plotinus.^[5] It is difficult to determine what, if anything, is different between the doctrines of Proclus and Syrianus: for the latter, only a commentary on Aristotle's Metaphysics survives, and Proclus never criticizes his teacher in any of his preserved writings.^[5]

The particular characteristic of Proclus's system is his elaboration of a level of individual ones, called henads, between the One which is before being and intelligible divinity.^[5] The henads exist "superabundantly", also beyond being, but they stand at the head of chains of causation (seirai) and in some manner give to these chains their particular character.^[5] He identifies them with the Greek gods, so one henad might be Apollo and be the cause of all things apollonian, while another might be Helios and be the cause of all sunny things. Each henad participates in every other henad, according to its character. What appears to be multiplicity is not multiplicity at all, because any henad may rightly be considered the center of the polycentric system.^{[citation needed]} According to Proclus, philosophy is the activity which can liberate the soul from a subjection to bodily passions, remind it of its origin in Soul, Intellect, and the One, and prepare it not only to ascend to the higher levels while still in this life, but to avoid falling immediately back into a new body after death.^{[citation needed]} Because the soul's attention, while inhabiting a body, is turned so far away from its origin in the intelligible world, Proclus thinks that we need to make use of bodily reminders of our spiritual origin.^{[citation needed]} In this he agrees with the doctrines of theurgy put forward by Iamblichus. Theurgy is possible because the powers of the gods (the henads) extend through their series of causation even down to the material world.^{[citation needed]} And by certain power-laden words, acts, and objects, the soul can be drawn back up the series, so to speak. Proclus himself was a devotee of many of the religions in Athens, considering that the power of the gods could be present in these various approaches.^{[citation needed]}

The majority of Proclus's works are commentaries on dialogues of Plato (Alcibiades, Cratylus, Parmenides, Republic, Timaeus). In these commentaries, he presents his own philosophical system as a faithful interpretation of Plato, and in this he did not differ from other Neoplatonists, as he considered that "nothing in Plato's corpus is unintended or there by chance", that "Plato's writings were divinely inspired" (ὁ θεῖος Πλάτων ho theios Platon—the divine Plato, inspired by the gods), that "the formal structure and the content of Platonic texts imitated those of the universe",^[6] and therefore that they spoke often of things under a veil, hiding the truth from the philosophically uninitiated. Proclus was however a close reader of Plato, and quite often makes very astute points about his Platonic sources.

In his commentary on Plato's Timaeus Proclus explains the role the Soul as a principle has in mediating the Forms in Intellect to the body of the material world as a whole. The Soul is constructed through certain proportions, described mathematically in the Timaeus, which allow it to make Body as a divided image of its own arithmetical and geometrical ideas.

In addition to his commentaries, Proclus wrote two major systematic works.^[7] The Elements of Theology (Στοιχείωσις θεολογική) consists of 211 propositions, each followed by a proof, beginning from the existence of the One (divine Unity) and ending with the descent of individual souls into the material world. The Platonic Theology (Περὶ τῆς κατὰ Πλάτωνα θεολογίας) is a systematization of material from Platonic dialogues, showing from them the characteristics of the divine orders, the part of the universe which is closest to the One.

We also have three essays, extant only in Latin translation: Ten doubts concerning providence (De decem dubitationibus circa providentiam); On providence and fate (De providentia et fato); On the existence of evils (De malorum subsistentia).^[7]

Proclus, the scholiast to Euclid, knew Eudemus of Rhodes' History of Geometry well, and gave a short sketch of the early history of geometry, which appeared to be founded on the older, lost book of Eudemus. The passage has been referred to as "the Eudemian summary," and determines some approximate dates, which otherwise might have remained unknown.^[8] The influential commentary on the first book of Euclid's Elements is one of the most valuable sources we have for the history of ancient mathematics,^[9] and its Platonic account of the status of mathematical objects was influential.

In this work, Proclus also listed the first mathematicians associated with Plato: a mature set of mathematicians (Leodamas of Thasos, Archytas of Taras, and Theaetetus), a second set of younger mathematicians (Neoclides, Eudoxus of Cnidus), and a third yet younger set (Amyntas, Menaechmus and his brother Dinostratus, Theudius of Magnesia, Hermotimus of Colophon and Philip of Opus). Some of these mathematicians were influential in arranging the Elements that Euclid later published.

Proclus authored a theology of Plato, which is text concerned with the divine hierarchies and their complex ramifications.

A number of his Platonic commentaries are lost. In addition to the Alcibiades, the Cratylus, the Timaeus, and the Parmenides, he also wrote commentaries on the remainder of the dialogues in the Neoplatonic curriculum.^[10] He also wrote a commentary on the Organon, as well as prolegomena to both Plato and Aristotle.^[10]

Proclus exerted a great deal of influence on Medieval philosophy, though largely indirectly, through the works of the commentator Pseudo-Dionysius the Areopagite.^[11] This late-5th- or early-6th-century Christian Greek author wrote under the pseudonym Dionysius the Areopagite, the figure converted by St. Paul in Athens. Because of this fiction, his writings were taken to have almost apostolic authority. He is an original Christian writer, and in his works can be found a great number of Proclus's metaphysical principles.^[12]

Another important source for the influence of Proclus on the Middle Ages is Boethius's Consolation of Philosophy, which has a number of Proclus principles and motifs.^{[citation needed]} The central poem of Book III is a summary of Proclus's Commentary on the Timaeus^{[citation needed]}, and Book V contains the important principle of Proclus that things are known not according to their own nature, but according to the character of the knowing subject.^[11]

A summary of Proclus's Elements of Theology circulated under the name Liber de Causis (Book of Causes).^[11] This book is of uncertain origin, but circulated in the Arabic world as a work of Aristotle, and was translated into Latin as such.^[11] It had great authority because of its supposed Aristotelian origin, and it was only when Proclus's Elements were translated into Latin that Thomas Aquinas realised its true origin.^[11] Proclus's works also exercised an influence during the Renaissance through figures such as Nicholas of Cusa and Marsilio Ficino. The most significant early scholar of Proclus in the English-speaking world was Thomas Taylor, who produced English translations of most of his works.^[11]

The crater Proclus on the Moon is named after him.

• Allegorical interpretations of Plato

• Article by Encyclopædia Britannica
• O'Connor, John J.; Robertson, Edmund F., "Proclus", MacTutor History of Mathematics Archive, University of St Andrews
• Editions and Translations Proclus – Hoger Instituut voor Wijsbegeerte
• Article at "The Encyclopedia of Goddess Athena"
• Five Hymns of Proclus Thomas Taylor translation.
• Fragments that Remain of the Lost Writings of Proclus Thomas Taylor translation.
• Commentaries of Proclus on the Timaeus of Plato, in Five Books Thomas Taylor translation.
• Ten Doubts Concerning Providence and On the Existence of Evils Thomas Taylor translation.
• Proclus's Life and Teachings
• Index page of the Proclus section for the "Plato Transformed" project at the University Leuven, Belgium.
• Commentary on Plato's Parmenides – (Greek text, scans of Cousin's edition)
• Catalogue of the Prometheus Trust "Thomas Taylor Series" which includes translations of many of the works of Proclus. The site has lengthy extracts of these.
• Scans of editions of Proclus' Hypotyposis and his commentary on Euclid 1 at wilbourhall.org (Classical Greek and Latin)
• On the Signs of Divine Possession – (partial translation of Proclus's work)
• On the Sacred Art – (translation and discussion of this surviving extract from a larger work by Proclus)
• On the Sacred Art (French introduction and Greek text)
• On the Sacred Art – Greek text and English translation
• Hypotyposis Astronomicon Hypotheseon – Greek text
• Proclus in English and Greek, Select Online Resources
• Works by Proclus at LibriVox (public domain audiobooks)
• Guide to Proclus, Elementa theologica. Manuscript, 1582 at the University of Chicago Special Collections Research Center