## 1. Life and Works




Since Proclus' extant works contain almost no evidence about
his biography, we have to rely on the information transmitted by his
direct pupil Marinus of Neapolis in the eulogy he devoted to his
predecessor *Proclus or on Happiness*. Moreover, some scattered
remarks on Proclus and valuable information about the schools in Athens
and Alexandria can be found in Damascius' *Life of
Isidorus* (called by other scholars *The Philosophical
History*). As with Porphyry's *Life of Plotinus*, both
Marinus' and Damascius' works are biographies written by
students praising extensively the achievements of their teachers both
in doctrine and in philosophical life.




On Proclus' works see Beutler (1957), 190-208, Saffrey-Westerink
(1968), lv-lx, Rosan (22009), 266-274, and
especially Luna-Segonds-Endress (2012), as well as the
short overview given below (1.2). Although a large part of his
numerous writings is lost, some major commentaries on Plato have
survived (though incomplete) and some important systematic
works. Moreover, later Neoplatonists such as Damascius, Olympiodorus,
Simplicius, and Philoponus have conserved many extracts of lost work,
but these fragments have never been collected (see now, however,
Luna-Segonds-Endress (2012)).


### 1.1 "Proclus or On Happiness" (Marinus' Life of Proclus)



*Proclus or On Happiness* sets out to prove that Proclus
reached in his life the culmination of happiness (*eudaimonia*)
and wisdom because he ascended the scale of all virtues, the natural,
the ethical, the political, the purifying, the intellectual, and the
so called theurgic virtues, the latter of which make humans 'act
with the gods.' (The different virtues have been interpreted in
various ways in the Neoplatonic tradition; ultimately they refer to
different stages in the purification and ascent of the human soul, see
Saffrey/Segonds 2001, lxix-c.) 




Proclus was born in
Constantinople/Byzantium (now Istanbul) into a rich Lycian family in 412. Not
long after his birth his parents returned to their hometown Xanthos in
Lycia, a maritime area of what is now southwest Turkey. He began his
education in Xanthos and moved from there to Alexandria (Egypt) to
pursue the study of rhetoric in order to become a lawyer, as was his
father. However, during a journey to Byzantium he discovered philosophy
as his vocation. Back in Alexandria he studied Aristotle and
mathematics. Marinus reports that the very gifted pupil easily learned
all of Aristotle's logical writings by heart.




In 430-431, 18 years old, Proclus moved to Athens, attracted by the
fame of the Platonic School there. He studied for two years under the
direction of Plutarch (of Athens; to be distinguished from the
1st-2nd c. philosopher/biographer), reading with
him Plato's *Phaedo* and Aristotle's *De*
*anima*. After Plutarch's death in 432, Syrianus became
the head of the Academy. Proclus followed with him the usual curriculum
of the school (going back to Iamblichus), reading first
Aristotle's works and after that entering the 'greater
mysteries,' the Platonic dialogues. Under Syrianus, Proclus also
came into contact with the older traditions of wisdom such as the
theology of the Orphics and the Chaldaean Oracles. Among
Syrianus' lost works we find a treatise *On the harmony of
Orpheus, Pythagoras and Plato with the Chaldaean Oracles*. As the
Suda lexicon attributes a work with this title also to Proclus, it is
not unlikely that he published Syrianus' treatise, adding
comments of his own. Since Syrianus and Proclus worked intensively
together for six years, Proclus was strongly influenced by his
teacher. On many occasions Proclus praises the philosophical
achievements of his teacher and he never criticizes him. Because of
this, it is almost impossible to distinguish between Proclus'
original contribution and what he adopted from Syrianus.




After Syrianus' death (437), Proclus succeeded as head of the
Athenian school, and he kept this position for almost fifty years until
his death in 485. His tight schedule of the day, starting with a prayer
to the sun at sunrise (repeated at noontime and at sunset), included
lectures, reading seminars, discussions with students, and literary
work of his own. Besides his philosophical activities, Marinus also
portrays Proclus as an experienced practitioner of theurgy
(*Life* *of* *Proclus*, SS 28-29; on theurgy
see below 3.6). The practice of these pagan rites could only be
continued in the private sphere of the School's grounds. Though
Proclus was in Athens a highly respected philosopher and had some
Christian students, he had to be prudent to avoid anti-pagan reactions.
Marinus tells that he had to go into exile for about one year to Lydia
(in Asia) to avoid difficulties (*Life of Proclus* SS
15).


### 1.2 Works (extant and lost)




Marinus notes that Proclus was an extremely industrious writer,
having an "unbounded love of work" (*Life of
Proclus* SS 22). Apart from an impressive teaching-load and
several other commitments, Proclus wrote every day about 700 lines
(about 20-25 pages). It is unlikely that Proclus
published all of them. However that may be, from
Proclus' extant works and the information about his lost works it
emerges that he was a productive writer indeed. Roughly two thirds of
Proclus' output is now lost and several works, especially his
commentaries on Plato, have been transmitted in a mutilated form.




Among Proclus' surviving works we have five commentaries on
Plato (on *Alcibiades*, *Cratylus*, *Republic*,
*Timaeus*, and *Parmenides*), one commentary on Euclid,
two manuals on physics and metaphysics respectively (*Elements of
Physics, Elements of* *Theology*), an astronomical work
(*Hypotyposis*), three monographs (*Tria opuscula)*
on providence, fate, and free will and the origin of evil, and the
*Platonic* *Theology*, which offers an impressive
*summa* of Plato's theology, as well as theological
*Hymns*. See the supplement on



> 
> Proclus' Works
>  (the main extant works).




Some of his works have been completely lost, such as his commentaries
on Aristotle (the Organon), of others only a few fragments remain.
See the supplement on



> 
> Proclus' Complete Works (extant,
> lost, and spurious) [cf. Luna-Segonds-Endress (2012)].




It is difficult to establish a chronology of Proclus' works.
The *Platonic* *Theology* is generally considered to be
his last work. In writing the *Theology* Proclus heavily depends
on his interpretation of the *Parmenides* and often refers to
his commentary on this dialogue, which must have been finished some
time before. We know from Marinus (*Life of Proclus* SS13)
that Proclus finished his *Commentary on the Timaeus* by the age
of 27. However, it cannot be excluded that Proclus rewrote or modified
it later. As the *Alcibiades* came at the beginning of the
curriculum in the school, its commentary may also be an early work. The
*Commentary on the Republic* is not a proper commentary, but a
collection of several essays on problems and sections in this dialogue.
These essays may have been written at different times in Proclus'
life and only later put together (by Proclus himself or by someone
else). The *Hypotyposis* (Exposition of Astronomical Hypotheses)
was written in the year after Proclus' exile in Lydia, but we do
not know when exactly that took place. The *Tria*
*opuscula* all deal with similar topics, but they need not have
been composed at the same time. There are plausible arguments to put
the second treatise, *On What Depends on Us*, some years
after the events forcing Proclus to go into exile. The first treatise,
which in some parts depends very much on Plutarch (of Chaironea,
1st-2nd c. C.E.), could be set earlier in his
career. It also contains a discussion on the nature of evil, which is
much simpler than what we find in the treatise *On the Existence of
Evils*, which is more sophisticated and probably was composed
later. Because of its introductory character, one may be inclined to
consider the *Elements* *of* *Physics* as an early
work. This has also been claimed for the *Elements* *of*
*Theology*, which, however, shows all the sophistication of
Proclus's mature thought. It may be possible that Proclus revised
this text several times in his career.


## 2. The Commentator of Plato




The center of Proclus' extensive *oeuvre* is without
doubt his exegesis of Plato, as is shown by the large commentaries he
devoted to major dialogues. This Platonic focus is also evident in the
composition of his systematic works. The *Platonic*
*Theology* offers a systematic exposition of theology based on
an interpretation of all relevant sections on the gods and their
attributes in Plato's dialogues, and in particular on the
*Parmenides*, considered as the most theological of all
dialogues. Proclus probably commented on all dialogues included in the
curriculum of the school since Iamblichus. In addition Proclus wrote
the commentary on the *Republic* mentioned above. The curriculum
consisted of altogether 12 dialogues distributed into two cycles. The
first cycle started with *Alcibiades* (on self-knowledge) and
ended with the *Philebus* (on the final cause of everything: the
good), comprising two dialogues on ethics (the *Gorgias* and the
*Phaedo*), two on logic (the *Cratylus* and the
*Theaetetus*), two on physics (the *Sophist* and the
*Statesman*), and two on theology (the *Phaedrus* and the
*Symposium*). The second cycle included the two perfect
dialogues that were considered to encompass Plato's whole
philosophy (*In Tim*. I 13.14-17), namely, the *Timaeus*
(on physics) and the *Parmenides* (on theology).




In the form and method of his commentaries, Proclus is again
influenced by Iamblichus. He assumes that each Platonic dialogue must
have one main theme (*skopos*) to which all parts of the
arguments ought to be related. To interpret the text, different
approaches are possible (theological, mathematical, physical, ethical
exegesis), but they are all interconnected according to the principle
'everything in everything' (*panta en pasin*). Thus,
the *Timaeus* has in all its parts as its purpose the
explanation of nature (*physiologia*). Even the introductory
sections, the summary of the discussion in the *Republic* and
the anticipation of the story about Atlantis, must be understood from
this point of view; for they contain, in the mode of 'images and
examples,' a description of the fundamental forces that are at
work in the physical world. Also the long treatise on human nature,
which concludes Timaeus' exposition, has ultimately a
cosmological meaning, as the human animal is a microcosmos wherein all
elements and all causes of the great universe are found. More
problematic was the determination of the *skopos* of the
*Parmenides*. In a long discussion with the whole hermeneutical
tradition since middle-Platonism, Proclus defends a theological
interpretation of the dialogue. According to him, the dialectical
discussion on the One and the Many (*ta alla*) reveals the first divine principles
of all things.




With the exception of the commentary on the *Cratylus*, of
which only a selection of notes from the original commentary
is preserved, the exegetical works of Proclus have a clear structure.
They divide the Platonic text in different lemmata or cited passages,
discussing first the doctrine exposed in the particular section
(*pragmata*, later called *theoria*), next commenting on
the formulation of the argument (called *lexis*) [see
Festugiere 1963]. Whereas modern scholars usually accept a
development in Plato's thought and distinguish between an early,
middle, and late Plato, the Neoplatonists take the Platonic corpus as
the expression of a divinely inspired and unitary philosophical doctrine.
This enables them to connect different Platonic dialogues into one
system and to see numerous cross-references within the Platonic
*oeuvre*. What may seem to be contradictions between statements
made in different dialogues, can be explained by different pedagogical
contexts, some dialogues being rather maieutic than expository, some
elenctic of the sophistic pseudo-science, some offering a dialectical
training to young students.




A Neoplatonic commentary offers much more than a faithful
interpretation of an authoritative text of Plato. Plato's text
gives the commentator an opportunity to develop his own views on the
most fundamental philosophical questions, the first principles, the
idea of the Good, the doctrine of the Forms, the soul and its
faculties, nature, etc. As was said, the two culminating dialogues, the
*Timaeus* and the *Parmenides*, offer together a
comprehensive view of the whole of Platonic philosophy: 



> 
> 
> Since the whole philosophy is divided into the study of intelligibles and the
> study of things within the cosmos - and quite rightly so, as the
> cosmos too is twofold, the intelligible and the sensible, as Timaeus
> himself will say in what follows (*Timaeus* 30c) - the
> *Parmenides* comprehends the study (*pragmateia*) of the
> intelligibles and the *Timaeus* the study of things within
> the cosmos. For the former teaches us all the divine orders and the
> latter all processions of things within the cosmos. (*In*
> *Tim*. I 12.30-13.7)




The interpretation of the
*Parmenides* thus prepares the way for the *Platonic
Theology*, offering the systematic structure for a scientific
demonstration of the procession of all the orders of gods from the first
principle. As Proclus explains at *Theol*. *Plat*. I 2,
p. 9.8-19, the *Platonic* *Theology* falls into three
parts (after a long methodological introduction). The first part
(*Theol*. *Plat*. I 13-29) is an investigation into the
common notions (*koinai* *ennoiai*) of the gods as we
find them in Plato's dialogues: it is a treatise on the divine
names and attributes. The second part (*Theol*. *Plat*.
II-VI), which is incomplete, unfolds in a systematic way the procession
of the divine hierarchies, from the One, that is the first god, to the
'higher kinds,' i.e., angels, *daimones*, and
heroes, while the third part, which is altogether missing, was supposed
to deal with the individual hypercosmic and encosmic gods.




Before presenting his own views, Proclus usually critically evaluates the
opinions and interpretations of his predecessors. In this respect,
his commentaries are a rich and indispensable source for the
history of Middle and Neo-Platonism. Thus, in his *Commentary on the
Timaeus* Proclus reports and criticizes the views of Atticus,
Numenius, Longinus, Plotinus, Porphyry, Iamblichus, Theodorus of Asine
and many others, ending usually in full agreement with the explanation
of his master Syrianus. Besides, in explaining Plato's text,
Proclus frequently seeks confirmation of his exegesis in the
*Chaldaean Oracles* or the Orphic tradition. As Syrianus (see Helmig
2009), Proclus is often very critical of Aristotle and refutes his
criticism of Plato's views. He is certainly not an advocate of
the "harmony of Plato and Aristotle," which became the
leading principle of the Alexandrian commentaries (of Ammonius and
Simplicius). Proclus notes significant differences between the two
philosophers in epistemology (theory of abstraction vs. learning as
recollection), metaphysics (first principle, theory of Forms, theory of
universals), physics (Plato's *Timaeus* vs.
Aristotle's *Physics*), political philosophy
(Aristotle's criticism of Plato's *Republic*), and
language (*Cratylus* vs. *De* *Interpretatione*).
According to Proclus, Plato is not only far superior to Aristotle in
his theology (as only Plato ascended beyond the intellect to posit the
One as the ineffable principle of all things), but in all other
philosophical disciplines, where we owe to him all important
discoveries. Whereas the Peripatetics were accustomed to defend the
superiority of Aristotle over Plato with reference to his impressive
physical project, Proclus considers the latter as inferior to the great
achievement of Plato in the *Timaeus* (see Steel 2003).
Aristotle's natural philosophy is the work of a zealous admirer,
a disciple who tried to be better than the master: 



> 
> 
> It seems to me that the excellent Aristotle emulated the teaching of Plato as far
> as possible when he structured the whole investigation about
> nature. (*In Tim*. I 6.21-24) 


 

Following Plato, Aristotle explains in his *Physics* the
general principles of natural things: form, matter, nature, the
essence and principles of movement, time and place; again taking
inspiration from the *Timaeus*, he studies in other works the
specific principles of the distinct regions of the physical world,
thus in the *De* *Caelo* the celestial and the sublunary
realm, and in *On generation and corruption* and
in *Meteorologica* the sublunary realm. In this domain, it
cannot be denied, Aristotle did much more than his master. According
to Proclus, however, he developed the subject 'beyond what is
needed'. The same remark must be made about Aristotle's
extensive zoological research. Whereas Plato limited himself in
the *Timaeus* to an analysis of the fundamental principles of
all living organisms, Aristotle gave most of his attention to the
material components of animals and scarcely, and only in few cases,
did he consider the organism from the perspective of the form. Plato,
on the contrary, when explaining the physical world, never got lost in
a detailed examination.


## 3. Philosophical views




When trying to determine Proclus' profile as a philosopher, one has to
keep in mind that Platonists were not keen on introducing new elements
into the Platonic doctrine. They despised innovation
(*kainotomia*). Yet it cannot be denied that Neoplatonic
philosophy differs considerably from what we read in Plato's
dialogues. There is also overwhelming evidence for continual
discussions in the school on the right interpretation of Plato or on
certain doctrinal points (such as the transcendence of the One, or the
question whether the soul wholly descended from the intelligible
world). In order to evaluate Proclus' originality, one ought to
compare his views with those of the Neoplatonists before him, such as
Plotinus, Porphyry, Iamblichus, and Syrianus. Only with regard to
Plotinus is this possible to a great extent, because we still have the
full corpus of Plotinus' writings. Proclus certainly admired the first
'founder' of the new Platonism and even devoted a
commentary to the *Enneads*, of which, alas, we have only some
fragments. He shared Plotinus' views on the three
principal *hypostases* the One, the Intellect and the Soul, and
often uses language inspired by his reading of Plotinus, as in his
description of the union of the soul with the ineffable One. Yet on
many points, he is very critical of Plotinus, pointing to
contradictions, rejecting provocative views such as the thesis that
One is cause of itself (*causa sui*), the doctrine of the
undescended soul, or the identification of evil with matter. Another
radical difference from Plotinus (and Porphyry) is the importance
attributed to theurgy for the salvation of the soul and the authority
of *Chaldaean Oracles*.




As said before, it is very difficult to mark off Proclus'
originality with regard to his teacher Syrianus, the only predecessor
he never criticizes. Of the literary production of the latter, we have
only his *Commentary on Aristotle's Metaphysics*. It is
possible that most of Syrianus' courses on Plato never were
published, but were continued and further worked out by
Proclus himself. We have, however, the commentary on the
*Phaedrus* by Hermeias, who was sitting together with Proclus,
in Syrianus' course. One gets the impression that Syrianus was
very interested in Orphic theogony, whereas for Proclus the
*Chaldaean* *Oracles* are more authoritative when
developing a Platonic theology. But here again, it is difficult to
compare as we do not possess Proclus' own commentary. Is Proclus
after all then not so original, but only an excellent teacher and
wonderful systematizer of the new Platonic doctrines which became
dominant in the school since Iamblichus on? We shall never know, and it
is after all not so important when assessing the philosophical merits
of his works. To praise Proclus' philosophical achievements,
Marinus devotes in *Life of Proclus* one chapter to the
discussion of the doctrines we owe to him (SS 23). Surprisingly,
for all his admiration for the master, he can only enumerate a few
innovative doctrines; and they are of such a minor importance that we
shall not even discuss them in this article.


### 3.1 Metaphysics and Theology




In late antiquity, Aristotle's *Metaphysics* was considered to
be a theological work, because Aristotle investigates in this treatise
the first principles of all being:



> 
> 
> This discipline may be called theology, because the
> principles of beings and the first and most perfect causes of things
> are what is most of all divine. (Asclepius, *In Metaph*.
> 4.1-3)


Indeed, there is precedent for this in Aristotle himself, for
in *Metaphysics* VI, 1, 1026a15ff, he classifies "first
philosophy," or metaphysics, as theology.




Proclus himself often uses the term 'theology' in this
metaphysical sense for the study of the first ('divine')
principles of all things. His *Elements of Theology* can in
fact be considered an introduction to his metaphysics. The work is a
concatenated demonstration of 217 propositions, which may be divided
into two halves: the first 112 propositions establish the One, unity
without any multiplicity, as the ultimate cause of reality and lay
down basic metaphysical concepts/structures such as causality,
participation, the relation of wholes to parts, infinity, and
eternity. The second half deals with the three kinds of true causes
within reality recognized by Proclus: gods (which he calls henads or
"unities," see below), intellects, and souls. This
elaborate metaphysical framework makes it possible for Proclus to
develop a scientific theology, i.e., a demonstration of the procession
and properties of the different classes of gods. In what follows we
will only discuss some characteristic features of Proclus' metaphysics
(see further Steel 2011).




On the whole, Proclus' doctrine of first principles is a further
development of Plotinus' innovative interpretation of Platonic
philosophy. With Plotinus, Proclus recognizes three fundamental levels
of reality called 'hypostases' (or self-subsistent
entities): One, Intellect, and Soul. However, following a concern of
his predecessor Iamblichus for greater precision in the relationship
and distinction between the One and Intellect, Proclus distinguishes
between the intelligible Being (*to noeton*--what is
the object of intellectual intuition) and the intellective (*to
noeron*--what is intelligizing), and introduces between both,
as an intermediary level, the
*noeton-noeron* (what is being intelligized and
intelligizing). These three ontological levels thus correspond to the
triad of Being, Life, and Intellect, which already play an important
role in Plotinus' and Porphyry's speculations about the procession or
'emanation' of the intelligible world from the One,
without, however, being hypostasized. Since Zeller (influenced by
Hegel) the application of the triadic structure to reality has been
seen as the characteristic feature of Proclus' system, but see Dodds
19632, pp. xxii and 220, on possible sources of the doctrine.




Although the distinction of aspects of reality as distinct
*hypostases* and the multiplication of triads might suggest a
loss of Plotinus' intuition of the unity of reality, it is
important to stress that each part of the triad of Being, Life and
Intellect, mirrors within itself their triadic relationship. This
redoubled triadic structure must be understood as expressing an
intrinsic and essential relation between successive levels of
being. The intimate relation between Being, Life, and Intellect is the
origin of the basic structure uniting all causes to their effects,
namely the relation of immanence, procession and reversion
(*mone-prohodos-epistrophe*, see *Elem.
Theol.* SS 35). This triad has been called the "triad of
triads," the underlying principle of all triadic structures:



> 
> Every effect remains in its cause, proceeds from it, and reverts upon
> it. For if it should remain without procession or reversion, it would
> be without distinction from, and therefore identical with, its cause,
> since distinction implies procession. And if it should proceed without
> reversion or immanence [sc. in the cause], it would be without
> conjunction or sympathy with its cause, since it would have no
> communication with it. And if it should revert without immanence
> [sc. in the cause] or procession, how can that which has not received
> its being from the higher revert existentially upon a principle thus
> alien? [*Elem. Theol.* SS 35, transl. E.R. Dodds]




Another fundamental triad is the triad
Unparticipated-Participated-Participating
(*amethekton-metechomenon-metechon*). Plato's theory of
participation, which explains the relation between the intelligible
world and the sensible reality it grounds, raised many problems,
several of which Plato himself brings up in the first part of
his *Parmenides*. Most pressing was the puzzle: How can a Form
be at the same time one and the same and exist as a whole in many
participants? (see Plato, *Parmenides* 131a-b). The basic idea
of the triad of participation, which can also be seen as responding to
Aristotle's criticism of participation, is to maintain the
transcendence, and hence, the unity of the Form, while allowing for
its presence in the participants. Thanks to the existence of an
'unparticipated' principle, that is, one that is not such
as to be participated in by anything, to which the
'participated' entities, the ones that are participated in
by something, are connected by means of "the triad of
triads" (*Elem. Theol.* SS 23), the universal nature
of the Form can be safeguarded.




Proclus, however, also applies this principle to explain the most
difficult problem facing Neoplatonic metaphysics, namely, how to
understand the procession of the manifold from the One. How can the
One be wholly without multiplicity, when it must somehow be the cause
of any and all multiplicity? The One remains in itself absolutely
unparticipated; the many different beings proceeding from it
participate in a series of participated henads or unities (gods).
According to some scholars it was Iamblichus who introduced this
innovative doctrine, others attribute it to Proclus' teacher
Syrianus. Even if the doctrine does not originate as such from
Iamblichus himself, the existence of the divine henads somehow follows
from his law of mean terms. This law states that "every
producing cause brings into existence things like to itself before the
unlike." (*Elem. Theol.* SS 28). Thus there are no leaps in
the chain of being, but everything is linked together by similar
terms. The henads fulfill this function, for as participated unities
they bridge the gap between the transcendent One and everything that
comes after it. The doctrine of the henads can thus be seen as a way
of integrating the traditional gods of Greek polytheistic religion
into the Neoplatonic metaphysics of the One.


### 3.2 Causality




a. *Auxiliary and true causes*. From Middle Platonism onwards,
various attempts were made to integrate the Aristotelian doctrine of
causes within the Platonic philosophy (see Steel 2003). In Plato's
work, it was argued, one can find the four types of causality that
Aristotle distinguishes, to wit formal, material, efficient, final,
and, besides, the paradigmatic cause, which Aristotle wrongly
rejected. This system of causes (with the addition of the instrumental
cause as a sixth) became standard in later Neoplatonism. In his
commentary on the *Timaeus*, Proclus observes that Aristotle
never rises to the proper level of causality. For the four causes, as
Aristotle understands them, can only be applied to the explanation of
processes in the sublunary world. In the Platonic view, however, the
material and formal causes are only subservient or instrumental
causes. Those causes are in fact immanent in their effects and
constitutive elements of the thing they produce. As Proclus asserts in
prop. 75 of the
*Elements of Theology*, "that which exists in the effect
is not so much a cause as an auxiliary cause (*sunaition*) or
an instrument of the producer." Causes in the proper sense must
act upon their effects from outside, while transcending them. For a
proper understanding of what the true causes are of all things,
Proclus argues, one must follow Plato, who lifts us up to the level of
the transcendent Forms and makes us discover the creative causality of
the demiurge and the finality of the Good as the ultimate explanation
of all aspirations.




Although Aristotle also discusses efficient and final causes, he
falls short of a true understanding of creative causality because he
abandons the hypothesis of the Forms. Without the transcendent Forms,
there can be no explanation of the being of things, only an explanation
of their movement and change. Given Aristotle's narrow
understanding of nature, it must come as no surprise, Proclus notices,
that he admits of cases of 'spontaneous generation' in the
sublunary realm, which again restricts the purport of efficient
causality. Moreover, because of his rejection of the demiurge (and of the One),
Aristotle is also forced to limit efficient causality to the sublunary
realm. In fact, in his view there is no cause of existence of the
celestial bodies or of the sensible world as a whole: they exist
necessarily in all eternity. But, as Proclus argues, such a position
will force him to admit that the world has the capacity to constitute
itself, which is absurd (see below).




The Neoplatonic concept of causality is therefore quite different from
that of the Peripatetics, even if both share the same terminology,
such as final or efficient cause. Aristotle's causes are primarily
intended to explain how things move and change, come to be and cease
to be, but also offer to explain *what* given things are. For
the Neoplatonists, generalizing a principle formulated in
the *Philebus* -- "that everything that comes to be
comes to be through a cause" (26e, cf. *Tim.* 28a)
-- causality is of much wider application than the explanation of
change and motion, it is not only about what things are, but about
what constitutes (*hupostatikos*) their being, and it can be,
analogously, used to explain relations between all levels of
being. Thus we can say of the One that it is the cause of Intellect,
and of Intellect that it is cause of Soul. In the *Timaeus*,
however, the main interest is to understand what is the cause of the
sensible world and all the cosmic beings: this is primarily the
demiurge or creator of the world (the One is not the
'creator' of Intellect).




b. *Corporeal and incorporeal causes.* According to the
Stoics only bodies and powers or qualities of bodies are capable of
acting and being acted upon (see Steel 2002). The Platonists often
criticized the Stoic view and pointed to what they thought were the
many contradictions involved, in particular, in the materialistic
explanation of psychic activities or dispositions such as virtues. They
defended the opposite view: all forms of causality must ultimately be
explained as emanating from incorporeal entities. Proclus adopts
Plotinus' view (IV, 7 [2] 8a), that only incorporeal beings can
be causes in the strict sense, and includes it among the basic theorems
of his metaphysics. See *Elem. Theol.* SS 80 (cf.
*Theol*. *Plat*. I 14, p. 61.23-62.1):



> 
> 
> Every body has by its own nature the capacity to be acted
> upon, every incorporeal thing the capacity to act, the former being in
> itself inactive, the latter impassive; but through association with the
> body, the incorporeal too is acted upon, just as bodies too can act
> because of the participation in incorporeal entities.




In this proposition Proclus first sets apart the corporeal and
incorporeal as being active/impassible and passive/inactive
respectively. However, the two realms are not absolutely separate from
each other. The soul, which is an incorporeal substance, enters into
association with the body and thus becomes itself, though only
accidentally, subject to different passions. The body, on the contrary,
may gain great profit from the association with the incorporeal. This
is evident in the case of animated bodies, which owe all their vital
activities to the presence of the soul in them. But also inanimate
natural bodies acquire all capacities and powers from nature and its
inherent *logoi* or organizing rational principles (see Steel
2002).




c. *The relation of cause to its effect*. The relation
between a cause and its effect is characterized by both similarity and
dissimilarity. For every cause produces something that is similar to
it, and every effect thus resembles its cause, though in a secondary
and less perfect way. But in so far as the effect is really
distinguished from its cause, it acquires its own characteristic form
of being, which was not yet developed on the level of its cause. For
this reason each thing can be said to exist in three manners
(*Elem*. *Theol*. SS 65). First, it is in itself as
expressing formally its own character (*kath' hyparxin*).
Second, it exists in a causal manner (*kat'*
*aitian*) being anticipated in its cause. Finally, it exists
as being participated (*kata* *methexin*) by the
next level of being, which is its effect. Thus life is a property of a
living organism as being participated by it. Life characterizes the
soul formally. Life also exists *qua* Form in the divine
mind. Finally, Proclus stresses that the higher a cause, the more
comprehensive it is, and the further its effects reach (*Elem*.
*Theol*. SS 57). All things, including matter, which
has in itself, apart from the forms existing in it, no
'being', participate in the One; all beings participate in
Being; all plants and animals participate in Life; all rational souls
participate in Intellect.


### 3.3 Psychology and Epistemology




Proclus' epistemology is firmly rooted in his theory of the
soul. For Proclus, souls as self-moving principles represent the lowest
level of entities that are capable of reverting upon itself (so called
self-constituted beings [*authypostata*], see *Elem*.
*Theol*. SS 40-51). They are incorporeal, separable from
bodies and indestructible/immortal (*Elem*.
*Theol*. SS 186-7). Yet, they are principles of life and of
movement of bodies (*Elem. Theol*. SS 188). In accordance
with Proclus' general metaphysical principles (cf. above 3.1),
from the unparticipated soul-monad proceed different kinds of
participated soul: divine souls, daemonic souls, human souls, souls of
animals). As with other Platonists, Proclus frequently discusses the
vexed question as to why a soul would descend into a body at all
('fall of the soul') (see Dorrie / Baltes (2002.2)
163-218). Moreover, the Neoplatonist distinguishes between
altogether three so-called vehicles (*ochemata*) of the
soul. The rational soul is permanently housed in the luminous
vehicle, while the non-rational soul is located in the pneumatic
vehicle. By being incarnated in a human body, soul, or rather, the
vegetative soul attains thus a (third) 'shell-like'
vehicle. The theory of the different vehicles or the psychic
'astral body,' familiar nowadays from modern theosophic theories,
fulfils several crucial functions in Neoplatonic psychology: it
explains (a) how an incorporeal soul can be linked to a body, (b) how
souls can move in space, (c) how souls can be punished after death (cf.
Plato's myths), (d) where certain faculties of
the soul such as imagination are located. Proclus distinguishes between two kinds
of vehicles, one mortal and the other immortal (*In*
*Tim*. III 236.31 ff. and *Elem*. *Theol*. SS
207-210). Proclus also adheres to the Platonic theory of
transmigration, but argues that human souls never enter animal bodies
as their constitutive forms. For only animal souls can be organizing
principles of animal bodies. If some rational souls are
'degraded' in the next life and forced to live in an animal
body because of their misdemeanour in this life, they are only
'relationally' (*schesei*) present to this animal
body.




Proclus distinguishes between the following faculties of soul: sense
perception, imagination (*phantasia*), opinion, discursive
thought, and intellection. While sense perception and imagination
belong to the non-rational soul, opinion forms the lowest level of
rationality. The aim of epistemological ascent is to free oneself
eventually from the lower psychic faculties, including the lower
rational ones, in order to enjoy a state of pure contemplation.




As with many other Platonists, Proclus' epistemology is based
on a theory of *innate knowledge* (in accordance with the
Platonic dictum that 'all learning is recollection
[*anamnesis*]'). Proclus refers to the innate
contents of the soul as its reason-principles (*logoi*) or Forms
(*eide*). These innate reason-principles constitute the
essence of soul. That is why they are called 'essential
reason-principles' (*logoi* *ousiodeis*)
(Steel 1997). The traditional translation reason-*principles*
was chosen on purpose, because on an ontological level these same
*logoi* serve as principles of all things. They are extended or
unfolded images of the Forms that exist in intellect; and by means of
them the world-soul with the assistance of Nature brings forth
everything. In other words, the psychic *logoi* are
instantiations of Platonic Forms on the level of soul as are the
*logoi* in Nature and the forms immanent in matter. According to
the fundamental Neoplatonic axiom *panta* *en*
*pasin* ('all things are in all things'), Forms
exist on all levels of reality. But the *logoi* in soul also
offer the principles of all knowledge and are the starting points of
demonstration. At *In Parm*. IV 894.3-18 (ed. Steel) Proclus
argues that only with reference to these notions within the soul
predication is possible (see Helmig 2008), since they are universal in
the true sense of the word. On the other hand, both transcendent
Platonic Forms and forms in matter are not taken to be universals
proper by Proclus. The former are rather intelligible particulars, as
it were, and cannot be defined (Steel 2004), while the latter are
strictly speaking instantiated or individualised universals that are
not shared by many particulars (see Helmig 2008, cf. above 3.1-2). For
this reason, it does not make much sense to talk about 'the
problem of universals' in Proclus.




It is another crucial assumption of Proclus' epistemology that
all souls share the same *logoi* (*Elem*. *Theol*.
SS 194-195). In terms of concept-formation this entails that
psychic concepts, once they are grasped correctly, are universal,
objective, and shareable (see Helmig (2012) 13-24). Moreover, if all souls share the same
*logoi*, and these *logoi* are the principles of
reality (see above), then by grasping the *logoi* souls come to
know the true principles or causes of reality. Already Aristotle had
written that to know something signifies to know its cause
(*Met*. A 3, 983a25-26 and *An*.
*Post*. I 2, 71b9-12). In his *Commentary on
Plato's Timaeus*, Proclus introduces an interesting
distinction. Taking his start from the problem of how we can recognise
certain objects, he considers the example of an apple. The different
senses tell us that there is something sweet, red, even, with a nice
smell. And while common sense (*koine*
*aisthesis*) can distinguish the different impressions of
the special senses, only opinion (*doxa*) is capable of saying
that the object there on the table is an apple. *Doxa* is able
to do this, because it has access to the innate *logoi* of the
soul. However, as Proclus explains (*In* *Tim*. I 248.11
ff.), opinion only knows the 'that' (*hoti*), that
is, it can recognize objects. Discursive thought (*dianoia*), on
the other hand, also knows the 'why' (*dihoti*),
that is, the causes of something. This distinction can also be
rephrased in terms of concepts, implying a distinction between factual
concepts that allow us to identify or recognise certain objects, and
concepts that fulfil an explanatory role. On the whole, Proclus'
reading and systematisation of Plato's doctrine of learning as
recollection makes Platonic recollection not only concerned with higher
learning, since already on the level of object recognition we employ
concepts that originate from the innate *logoi* of the soul (Helmig (2012) 299-333).




Proclus argues at length that the human soul has to contain innate
knowledge. Therefore, one should not consider it an empty writing
tablet, as Aristotle does (Aristotle, *De anima* III 4). He is
wrong in asserting that the soul contains all things
potentially. According to Proclus, the soul contains all things (i.e.,
all *logoi*) in actuality, though due to the 'shock of
birth' it may seem as if the soul has fallen to
potentiality. At *In*
*Crat*. SS 61, Proclus asserts that the soul does not
resemble an empty writing tablet (*agraphon*
*grammateion*) and does not possess all things in potentiality,
but in act. *In* *Eucl.* 16.8-13 expresses the same
idea: "the soul is not a writing tablet void of *logoi*,
but it is always written upon and always writing itself and being
written on by the intellect." As with his philosophy of
mathematics, Proclus presents a detailed criticism of the view that
universal concepts are derived from sensible objects (by abstraction, induction, or
collection). In the fourth book of his *Commentary on
Plato's Parmenides* and in the two prologues of the
*Commentary on Euclid* we find the most comprehensive criticism
of abstractionism in antiquity (see Helmig (2010) and (2012) 205-221).


### 3.4 Ethics (Providence, fate, freedom of choice, evil)




Proclus devoted three entire books or 'monographs'
(*monobiblia*) to problems of providence, fate, free choice, and
evil. The first treatise (*Ten problems concerning providence*)
examines ten different problems on providence that were commonly
discussed in the Platonic school. For Proclus providence
(*pronoia*) is the beneficent activity of the first principle
(the 'source of goods') and the gods (henads), who have
their existence before intellect (*pro*-*nou*). One of
the problems discussed is the question of how divine foreknowledge and
human free choice can be reconciled. For if god knows not only past and
present, but also future events, the outcome of future events is
already pre-determined (as god has a determinate knowledge of all
things), and hence there is no free choice for humans. Proclus'
answer, which ultimately goes back to Iamblichus, consists in applying
the principle that *the mode of knowledge is not conditioned by the
object known but by the knower*. In the case of gods, this entails
that they know the contingent event in a non contingent manner, the
mutable immutably. They have an undivided knowledge of things divided
and a timeless knowledge of things temporal (*Elem*.
*Theol*. SS 124, cf. *De decem dub*. SS 6-8).
Proclus' answer was later taken up by Ammonius in his
*Commentary on the De Interpretatione* IX and in Boethius'
*Consolation of Philosophy* V 6 as well as in his *Commentary
on the De Interpretatione* IX.




The second treatise (*On providence fate and what depends on
us*) replies to a letter of Theodore, a former friend of Proclus.
In this letter Theodore, an engineer, had defended with several
arguments a radical determinism, thus entirely excluding free choice.
Before refuting Theodore's arguments, Proclus introduces some
fundamental distinctions in order to solve the problems raised by his
old friend. The first distinction is between providence and fate:



> 
> 
> Providence is essentially a god, whereas fate is something
> divine, but not a god. This is because it depends upon providence and
> is as it were an image of it. (*De prov*. SS 14) 




The second distinction is that between two types of soul: the rational soul
is separable from the body, the irrational resides in the body is
inseparable from its substrate; "the latter depends in its being
upon fate, the former upon providence" (*De prov*. SS
15 ff.). The *third* distinction concerns knowledge and truth:



> 
> 
> One type of knowledge exists in souls that are bound to the
> process of generation; [...] another type is present in souls that
> have escaped from this place. (*De* *prov.* SS
> 3.1-4.3) 


 

These three distinctions taken together make it possible for
Proclus to ultimately reconcile providence, fate, and free choice. In so
far as we are rational agents and let ourselves being determined in our
choices only by intelligible principles, we may transcend the
determinism of fate to which we belong as corporeal beings. Yet, our
actions are integrated into the providential order, as we willingly
obey the divine principles.




The third treatise (*On the existence of evils*) asks why and
how evil can exist if the world is governed by divine providence.
Proclus argues that evil does not have an existence of its own, but
only a derivative or parasitic existence (*par-hypostasis*, sc.
on the good) (*De* *mal*. SS 50). 



> 
> 
> In order to exist in a proper sense, an effect must result from a cause which
> proceeds according to its nature towards a goal that is intended.
> [...] Whenever an effect is produced that was not intended or is
> not related by nature or *per* *se* to the agent, it is
> said to exist besides (*para*) the intended effect,
> parasitically upon it, as it were. (Opsomer-Steel 2003, 25) 




This is precisely the case with evils, which are shortcomings and mistakes.
As a failure is never intended *qua* failure by an agent, but is
an unfortunate by-effect of its action, so is evil *qua* evil
never caused by a cause. Therefore, Proclus continues, it is better to
call its mode of existence a parhupostasis, rather than a hupostasis, a
term that belongs to those beings "that proceed from causes
towards a goal." Parhupostasis or "parasitic
existence," on the contrary, is the mode of existence of
"beings that neither appear through causes in accordance with
nature nor result in a definite end." 



> 
> 
> Evils are not the outcome of goal-directed processes, but happen *per accidens*,
> as incidental by-products which fall outside the intention of the
> agents. [...] Therefore it is appropriate to call such generation
> a parasitic existence (*parhupostasis*), in that it is without
> end and unintended, uncaused in a way (*anaition*
> *pos*) and indefinite. (*De* *mal*.
> SS 50.3-9, 29-31, transl. by Opsomer-Steel 2003) 




Dionysius the Areopagite adopted Proclus' views on evil in his
work *On the Divine Names*. Thanks to this adaptation
Proclus' doctrine of evil had an enormous influence on the later
medieval discussions on evil both in Byzantium and in the Latin West
and dominated the philosophical debates on evil up to the
19th century.


### 3.5 Physics, Astronomy, and Mathematics


#### A theological physics




Although Proclus composed a short (presumably early) treatise where
he summarises Aristotle's theory of movement (*Elements of
Physics*), he does not understand *Physics* primarily as the
study of movement and change of natural phenomena, but rather seeks to
connect these phenomena to their intelligible and divine causes
(*Physics* as a kind of *Theology*, *In*
*Tim*. I 217.25). In the preface to his commentary on
Plato's *Timaeus* Proclus sets out to prove why
Plato's physics, as developed in the *Timaeus*, is
superior to natural science in the Aristotelian sense (see Steel 2003).
In Proclus' view Plato's *Timaeus* not only offers a
*physiologia*, a science of nature in its many aspects, but also
presents an explanation of the whole of nature by paying due attention
to its incorporeal, divine causes: the natural world proceeds from the
demiurge as the expression of an ideal paradigm and aims at the ultimate
Good. Therefore, Plato's *physio*-logy is also a sort of
*theo*-logy:



> 
> 
> The purpose of *Timaeus* will be to consider the
> universe, insofar as it is produced by the gods. In fact, one may
> consider the world from different perspectives: insofar as it is
> corporeal or insofar as it participates in souls, both particular and
> universal, or insofar as it is endowed with intellect. But Timaeus will
> examine the nature of the universe not only along all those aspects,
> but in particular insofar as it proceeds from the demiurge. In that
> respect the physiology seems also to be a sort of theology, since also
> natural things have somehow a divine existence insofar as they are
> produced by the gods. (*In* *Tim*. I
> 217.18-27)




Before offering an explanation of the generation of the world,
Timaeus sets out the fundamental principles that will govern his whole
explanation of the physical world (*Tim*. 27d5-28b5). As Proclus
observes, it is the task of a scientist to formulate at the start of
his project the principles proper to the science in question, and not
just to assume some general axioms. The science of nature too is based
on specific axioms and assumptions, which must be clarified before we
can move to the demonstration. In order to make *phusiologia* a
real science, the philosopher must deduce his explanation, as does the
geometer, from a set of fundamental propositions or axioms.



> 
> 
> If I may say what I think, it seems to me that Plato proceeds
> here in the manner of the geometers, assuming before the demonstrations
> the definitions and hypotheses through which he will make his
> demonstrations, thus laying the foundations of the whole science of
> nature. (*In* *Tim*. I.217.18-27)
> 
> 




Starting from these fundamental propositions, Proclus argues, Plato
deduces the different types of causality that are required for a truly
scientific understanding of nature (efficient, exemplary, and final
cause; see Steel 2003 and above 3.2).


#### Time and eternity




Proclus discusses eternity and time in his commentary on the
*Timaeus* and in propositions 53-55 of the *Elements of
Theology* (see Steel 2001). Aristotle had defined time as a
"measure of movement according to the before and after."
Therefore, anything measured by time must have a form of existence or
activity in which a past and a future state can be distinguished. In
fact, an entity in time is never wholly and simultaneously what it is,
but has an existence extended in a process of before and after. Opposed
to it stands the eternal, which exists as a simultaneous whole and
admits of no composition or change. "There is no part of
it," writes Proclus, "which has already subsisted and
another that will subsist later, but as yet is not. All that it is
capable of being, already possesses it in entirety without losing it or
without accumulating" (*Elem*. *Theol*. SS 52).
One must distinguish the temporality of things in process from the time
by which they are measured. Temporal things participate in time,
without being time. "Time exists prior to all things in
time" (*Elem. Theol*. SS 53). 




With Iamblichus, Proclus distinguishes absolute time, which is not
participated in and exists 'prior' to all temporal things,
from participated time, or rather the many participated times. The same
distinctions must also be made regarding eternity. For Eternity
precedes as cause and measures the multiple eternal beings that
participate in it. "Every Eternity is a measure of things
eternal, every Time of things in time; and these two are the only
measures of life and movement in things" (*Elem*.
*Theol*. SS 54). To conclude, there are two measures of the
duration of things. First there is eternity, which measures at once the
whole duration of a being. Second, there is time, which measures
piecemeal the extension of a being that continually passes from one
state to another. Eternity can be seen as the prefiguration of time;
time as the image of eternity. Each of them governs a separate sphere
of reality, eternity the intelligible being, time the temporal
(corporeal and psychic) world of change. 




Notwithstanding the sharp distinction between the temporal and the
eternal realm, there are beings that share in both eternity and
time. As Proclus notes in the corollary
to *Elem*. *Theol*. SS 55, "of the things
which exist in time, some have a perpetual duration." Thus the
universe as a whole and the celestial spheres in it are
*both* eternal *and* temporal. They are eternal because
they never come to existence in time and never will cease to exist. But
they are temporal because they possess their being only through a
process of change in a sequence of moments. The same holds true for the
psychic realm: all souls are immortal and indestructible; nevertheless,
they are continually undergoing change. Therefore, as Proclus says,
"'perpetuity' (*aidiotes*) is of two
kinds, the one eternal (*aionion*), the other in time;
[...] the one having its being concentrated in a simultaneous
whole, the other diffused and unfolded in temporal extension
(*paratasis*); the one entire in itself, the other composed of
parts, each of which exists separately in a sequence of prior and
posterior." (*Elem. Theol.* SS 55, trans. Dodds,
modified).


#### The eternity of the world




Against Aristotle's critique in *De Caelo* I 10, Proclus
defends the view that the cosmos is "both eternal and generated
(*genetos*)." As a corporeal being, the universe
cannot produce itself and maintain itself in being. It depends for its
existence upon a superior cause, and it is for that reason
"generated." This does not prevent it, however, from
existing for ever, in an infinite time. As we just saw, Proclus
distinguishes between what is eternal in an absolute sense (the
intelligible realm) and what is eternal because it continues to exist
for the whole of time, what Boethius later called
"*aevum*" in distinction from
"*aeternum.*" As Proclus notices, at the end of the
*Physics* (8.10, 266a27-28), Aristotle himself
establishes that no body can possess from itself an unlimited power to
exist. If the world exists eternally, it must have this power from an
incorporeal principle. Therefore, Aristotle too is forced to admit that
the world is somehow generated, though it continues to exist for
eternity. For it always receives from its cause its infinite power and
never possesses it at once as a whole, because it is limited. The world
is eternal, because it has an infinite power *of coming to be*,
not because it exists of infinite power (*In* *Tim*. I
252.11-254.18).




This disagreement between Plato and Aristotle is ultimately due to a
different view about the first principles of all things. Aristotle
denies the existence of Platonic Forms and therefore cannot admit an
efficient or creative cause of the universe in the true sense of the
word. Efficient causality only concerns the sublunary world. The
celestial bodies and the world as a whole have no efficient cause of
their being, but only a final cause. From this misunderstanding about
the first principles follow all the other views that distinguish
Aristotle from Plato. One gets the impression, Proclus says, that
Aristotle, because he could not grasp the first principle of all things
- the One - has always to find an explanation of things on a
lower level:



> 
> 
> Whatever Plato attributes to the One, Aristotle attributes to
> the intellect: that it is without multiplicity, that it is object of
> desire, that it does not think of secondary things. Whatever Plato
> attributes to the demiurgic intellect, Aristotle attributes to the
> heaven and the celestial gods. For, in his view, creation and
> providence come from them. Whatever Plato attributes to the substance
> of heavens [sc. time], Aristotle attributes to their circular motion.
> In all these issues he departs from the theological principles and
> dwells upon the physical explanations beyond what is needed.
> (*In Tim*. I 295.20-27)


#### The celestial bodies and the place of the universe




Related to the eternity of the world is the question of the nature of
the celestial bodies. Aristotle argues in *De Caelo* I 2 that
the celestial bodies, which move with a natural circular motion, must
be made of a simple substance different from the four sublunary simple
bodies (whose natural movements are in a straight line: up or down).
This 'fifth element,' which is by nature imperishable, is
the ether. With this explanation Aristotle seems to oppose the view
Plato defends in *Timaeus* where it is said that the Demiurge
made the divine celestial bodies "mostly out of fire"
(40a2-4). Proclus admits that the heaven is composed out of the
four elements with a preponderance of fire, but he insists that the
elements are not present in the celestial bodies in the same mode as
they exist in the sublunary bodies. Therefore Aristotle is right when
he considers the heavens to constitute a fifth nature besides the four
elements. "For in the heavens the elements are not the same as
they are here, but are rather the summits of them"
(*In* *Tim*. II 49.27-29). If one counts the whole
heaven composed out of the best of the elements as one nature and adds
to it the four sublunary elements, we may speak of five natures
altogether.




Contrary to Aristotle, Proclus argues that the whole universe (*to
pan*) is in a place (*topos*). He can do this because his
conception of place differs in many respects from Aristotle's own. The
latter defined place as "the unmoved limit of the surrounding
body" (*Physics* IV 4, 212a21-22). From
this it follows as a necessary corollary that the universe as a whole
cannot be in a place, because there is simply nothing outside
it. Aristotle's definition, as we learn from Simplicius' and
Philoponus' *Corollary on Place*, had been criticized by all
later Neoplatonists (Syrianus, Proclus, Damascius, Simplicius, and
Philoponus). It is notable that Proclus' own theory of place, as
reported by Simplicius, differs considerably from other Neoplatonic
theories in that he considered place an immaterial 'body',
namely a special kind of immobile light. As emerges from
Proclus' *Commentary on Plato's Republic*, his theory took
inspiration from the column of light mentioned at
*Republic* X, 616b.


#### Astronomy




Since the heavenly bodies were considered divine, because they are
eternal and living beings, the study of the heavens was of special
importance to Neoplatonists. In the preface to his treatise *On
Astronomical Hypotheses* (a summary and evaluation of astronomical
views of his time), Proclus makes it clear that his approach is based
on Plato's remarks on astronomy (especially in the
*Republic* and in the *Laws*). He feels the need to go
through the different theories, because one can observe a great
disagreement among ancient astronomers on how to explain the different
phenomena (*Hyp*. I SS 33). Fundamental to Proclus'
approach is the distinction between two kinds of astronomy
(*Hyp*. I SS 1-3). The first kind contents itself with
observing the heavenly phenomena and formulating mathematical
hypotheses to explain them and make calculations and prognostics
possible. This is the astronomy as practiced by the most famous
astronomers before Proclus' time (Aristarchus, Hipparchus, and
Ptolemy). The second, which is developed by Plato in the
*Timaeus*, and is confirmed by the tradition of the
"Chaldaeans and Egyptians," investigates into the
intelligible causes of heavenly movements. An example for this approach
can be found in his *Commentary on Plato's Republic*
(*In* *Remp*. II 227.23-235.3). There,
Proclus explains that the seemingly irregular movements of the
planets ought not to be explained by means of Ptolemy's
complicated theory of excentric spheres and epicycles, but are rather
due to the fact that the planets are moved by intelligent souls which
express in the movements of their bodies "the invisible powers of
the Forms" (232.1-4). Yet Proclus appreciates Ptolemy's
astronomy as long as it is seen only as a mathematical-mechanical
construction making it possible to calculate and predict the positions
of planets, and as long as it does not claim to have any real
explanatory value. For the history of astronomy Proclus'
*Astronomical Hypotheses* remains a most valuable document,
since it represents one of the best introductions to Ptolemy's
*Almagest* extant from antiquity and since it explains the most
important ancient astronomical theories, in order finally (in chapter
seven of the work) to evaluate them critically. Proclus'
arguments also played an important role in the scientific discussion of
the Ptolemaic hypotheses in the 16th and 17th
century.


#### Mathematics




Proclus' distinctively non-empirical approach towards physics
and astronomy also influences his philosophy of mathematics, which is
set out in the two prologues to his commentary on the first book of
Euclid's *Elements*. The first prologue deals with the
mathematical sciences in general, while the second prologue focuses on
geometry proper. Proclus argues in great detail that the objects of
mathematical sciences cannot be derived from sensible particulars by
means of abstraction. Because of the imperfect and deficient
character of the sensible objects one cannot derive from them objects
that are as perfect and as precise as mathematical objects are.
Therefore, mathematical objects reside primarily in intellect and
secondarily in souls (as *logoi*). As universal concepts (cf.
3.2) we can grasp mathematical objects by means of recollection
(*anamnesis*). Since geometrical objects are not
universal, but particulars, and since by definition they possess
extension, Proclus argues that their place is human imagination
(*phantasia*). Imagination acts as a mirror and provides the
mathematical objects which are projected into it by the soul with
intelligible matter. By means of the latter geometrical objects gain
extension and particularity. As with physics and astronomy, the
ultimate aim of geometry is not the study of these extended, material
objects. Rather, geometry serves an anagogical task (just as in
Plato's *Republic*), leading the soul upwards to a study
of the true and unextended causes of geometrical objects in the divine
mind (*In* *Eucl*. 54.14-56.22).


### 3.6 Theurgy




Relying on Plato, *Theaetetus* 176a-b late Platonists saw the
assimilation to god (*homoiosis* *theoi*) as
the goal (*telos*) of philosophy. Proclus was faithful to this
ideal, as is attested by his biographer Marinus (*Life of
Proclus* SS 25). There was a fundamental discussion in late
Neoplatonism on how this assimilation to the divine was
possible for humans. Damascius (*In* *Phaed*. I SS 172
Westerink) distinguishes two tendencies: Plotinus and Porphyry
preferred philosophy, which makes us understand the divine principles
of reality through rational explication, while others like Iamblichus
and his followers, Syrianus, and Proclus, gave priority to hieratic
practice or theurgy (*theourgia*, *hieratike* [sc.
*techne*]). Their different evaluation of respectively
theory and theurgy as means of salvation may be explained by their
different views on the human soul and its possibilities of ascent to
the divine realm. While Plotinus and Porphyry claimed that the
superior part of the human soul always remains within the intelligible
realm, in touch with the divine principles, and never completely
descends into the body, Iamblichus, followed by Proclus, criticised
such a view. The soul does indeed wholly descend into the body (Steel
1978, 34-51). Hence the importance of theurgic rites established
by the gods themselves, to make it possible for the human soul to
overcome the distance between the mortal and the divine, which cannot
be done through increasing philosophical
understanding. In *Theol*. *Plat*. I 25, Proclus
expresses his great admiration for the power of theurgy, which
surpasses all human knowledge.




Allegedly, Neoplatonic theurgy originated with Julian the theurgist,
who lived in the time of emperor Marcus Aurelius. At first sight,
theurgy seems to share many characteristics with magic (theory of
cosmic sympathy, invocations, animation of statues of gods and demons),
but it is, as far as we can judge from the extant sources, clearly
different from it. In his *De* *Mysteriis* Iamblichus
developed a theology of the hieratic rituals from Platonic principles,
which clearly sets them apart from the vulgar magical practices. While
magic assumes that the gods can be rendered subservient to the
magicians, Platonic philosophers consider this impossible. According to
Plato's principles of theology (*Republic* II and
*Laws* X), the gods are immutable, unchangeable, and cannot be
bribed by means of sacrifices. Proclus' views on theurgy (of which
only some fragments belonging to his treatise *On Hieratic Art*
[i.e., theurgy] survived) are fully in line with these fundamental
Platonic axioms. But how, then, does theurgy work? The theurgists take
up an old belief, shared also by many philosophers, namely the natural
and cosmic 'sympathy' (*sumpatheia*) pervading all
reality. As with an organism, all parts of reality are somehow linked
together as one. Another way of expressing this idea is in the
Neoplatonic principle, going back at least to Iamblichus, that
everything is in everything (*panta*
*en* *pasin*). According to Proclus, all reality,
including its most inferior level, matter, is directed upwards towards
the origin from which it proceeds. To say it in the words of Theodorus
of Asine, whom Proclus quotes in his *Commentary on the Timaeus*
(I 213.2-3): "All things pray except the First." 




As stated before (cf. 3.3), the human soul contains the principles
(*logoi*) of all reality within itself. The soul carries,
however, also *sumbola* or *sunthemata* which
correspond to the divine principles of reality. The same symbols also
establish the secret correspondences between sensible things (stones,
plants, and animals) and celestial and divine realities. Thanks to
these symbols, things on different levels (stones, plants, animals,
souls) are linked in a 'chain' (*seira*) to the divine principle on
which they depend, as the chain of the sun and the many solar beings,
or the chain of the moon. Of great importance in the rituals was also
the evocation of the secret divine names. In his *Commentary on the
Cratylus*, Proclus compares divine names to statues of the gods
used in theurgy (*In* *Crat*. SS 46), pointing to
the fact that also language is an important means in the ascent to the
divine.




Proclus evokes the Platonic background of his theurgical beliefs,
namely his theory of love (*eros*) as expressed in
the *Symposium* and the *Phaedrus*, in his
treatise *On Hieratic Art*:



> 
> 
> Just as lovers move on from the beauty perceived by the
> senses until they reach the sole cause of all beautiful and
> intelligible beings, so too, the theurgists (*hieratikoi*),
> starting with the sympathy connecting visible things both to one
> another and to the invisible powers, and having understood that all
> things are to be found in all things, established the hieratic
> science. (trans. Ronan, modified)




In the wake of an article of Anne Sheppard (1982), scholars usually
distinguish between three kinds of theurgy in Proclus. The first kind,
as described in the above quoted treatise *On Hieratic Art*, was
mainly concerned with animating statues (in order to obtain oracles or
to evoke divine apparitions) or, in general, with activities related to
physical phenomena or human affairs (influencing the weather, healing
illnesses etc.) (see *Life of Proclus* SS 28-29). As emerges
from our sources, it is this kind of theurgy that involved much
ritualistic practice, including hymns and prayers. The second kind of
theurgy makes the soul capable of ascending up to the level of the
hypercosmic gods and the divine intellect. This second kind too
operates by means of prayers and invocations and it seems especially
characteristic of Proclus' *Hymns*. And finally, the third
kind of theurgy establishes unity with the first principles, that is
the One itself. This third kind corresponds to the level of the highest
virtues (i.e., 'theurgic virtues') in the scale of virtues.
It is not clear whether some form of ritual is involved here at all.
For this last stage of the Platonic *homoiosis*
*theoi* the following elements are of major importance:
negative theology (culminating in the negation of the negation), mystic
silence and the intriguing notion of faith (*pistis*), which
thus enters with a non-Platonic meaning - though even for the latter
notion Proclus will search for confirmation in the Platonic
dialogues.



> 
> 
> Those who hasten to be conjoined with the Good, do no longer
> need knowledge and activity, but need to be established and a stable
> state and quietness. What then is it which unites us to the Good? What
> is it which causes in us a cessation of activity and motion? What is it
> which establishes all divine natures in the first and ineffable unity
> of goodness? [...] It is, in short, the faith (*pistis*) of
> the Gods, which ineffably unites all the classes of Gods, of daemons,
> and of blessed souls to the Good. For we should investigate the Good
> not through knowledge (*gnostikos*) and in an
> imperfect manner, but giving ourselves up to the divine light, and
> *closing* *the* *eyes*, to become thus established
> in the unknown and occult unity of beings. For such a kind of faith is
> more venerable than cognitive activity, not in us only, but with the
> Gods themselves. (Proclus, *Platonic* *Theology*,
> I 25, trans. Th. Taylor, modified).


## 4. Influence




In his *Lectures on the History of Philosophy*, in the
chapter on Alexandrian Philosophy, Hegel said that "in Proclus we
have the culminating point of the Neo-Platonic philosophy; this method
in philosophy is carried into later times, continuing even through the
whole of the Middle Ages. [...] Although the Neo-Platonic school
ceased to exist outwardly, ideas of the Neo-Platonists, and specially
the philosophy of Proclus, were long maintained and preserved in the
Church."




That Proclus, who set up his elaborate *Platonic*
*Theology* in an attempt to rationally justify a pagan religious
tradition whose existence was threatened by the upcoming Christian
civilization, would have had such an influence in Christian medieval
thought might seem surprising. His influence, however, is mainly
indirect, as his ideas circulated under the names of other
philosophers. There was, of course, a direct confrontation with the
works of Proclus in the later Neoplatonic school (via Damascius and
Ammonius, 5th-6th century) and in Byzantium. In the
11th century, Michael Psellus studied Proclus intensively
and even preserved fragments of his lost works. One of his disciples
was the Georgian Ioanne Petritsi, who translated Proclus'
*Elements* into Georgian and composed a commentary on it
(Gigineishvili 2007). In the 12th century, bishop Nicolaus
of Methone wrote a Christian reply to Proclus' *Elements*,
thus showing indirectly that the work was still attracting interest.
Moreover, Isaac Sebastocrator (11-12th century) produced a
Christian adaption of the *Tria opuscula.* Around 1300 Proclus
attracted the interest of the philosopher George Pachymeres, who
prepared an edition of Proclus' *Commentary on
the Parmenides*, which was only preserved in a very corrupt
tradition, and even composed a commentary to the last part of the
dialogue where Proclus' commentary was lacking. Cardinal
Bessarion was an attentive reader of Proclus' works and possessed
several manuscripts. We owe to the interest of scholars such as
Psellus, Pachymeres, and Bessarion, the preservation of the work of the
pagan Proclus, who had not such a good reputation in theological
circles in Byzantium. And yet, the number of direct readers of Proclus
before the Renaissance was very limited.




During the Middle Ages Proclus' influence was mainly indirect, above all
through the writings of the Christian author Dionysius the Areopagite
and the Arabic *Liber de causis*. Dionysius was a Christian
author writing around 500, who was deeply fascinated by Proclus. He
fully exploited Proclus' works - which he must have read
intensively -- to develop his own original Christian Platonic theology.
He presented himself as a disciple of Saint Paul, a pretence which was
generally accepted until the late 19th century, thus giving
his works, and indirectly Proclus' theology, an almost apostolic
authority. As Dodds 19632, xxviii, has nicely put it:
"Proclus was [...] conquering Europe in the guise of an
early Christian." The well known *Book of Causes* is an
Arabic adaption of the *Elements of Theology*, made in the
9th century. Translated in the 12th century, the
*Liber de causis* circulated in the Middle Ages under the name
of Aristotle, and was considered as a complement to the
*Metaphysics*, offering a treatise on the divine causes. The
text entered the corpus of Aristotelian works and was intensively
studied and commented at the universities. Thomas Aquinas is the first
to have discovered that this work derived in fact from Proclus'
*Elements of Theology*, of which he had obtained a Latin
translation made by his Dominican confrere William of Moerbeke in 1268
(see Thomas Aquinas, *Commentary on the Liber de causis*,
introduction). Moerbeke also translated the *Tria*
*opuscula* and the huge commentary on the *Parmenides*,
but these works had almost no readers in the Middle Ages. Berthold of
Moosburg wrote in the 14th century a comprehensive
commentary on the Latin *Elements of Theology* . The real
rediscovery of Proclus started in the Italian Renaissance, mainly
thanks to Marsilio Ficino who followed Proclus' influence in his
Platonic commentaries and even composed, in imitation of Proclus, a
Christian *Platonic Theology* on the immortality of the soul.
Before Ficino, Nicolaus Cusanus had already intensively studied
Proclus in translations. Proclus continued to enjoy wide interest at
the turn of the 18th century. Thomas Taylor (1758-1835)
translated all of Proclus' works into English (reprinted by the
Prometheus Trust [London]) and tried to reconstruct the lost seventh
book of the
*Platonic* *Theology.* Victor Cousin (1792-1867) aimed at
a complete edition of his preserved work. At the beginning of the
20th century we have the great editions of commentaries in
the Teubner collection. Renewed philosophical interest in Proclus in
the last century started with the edition of the *Elements of
Theology* by Eric Robertson Dodds, and carried on with the edition of the
*Platonic Theology* by Henry Dominique Saffrey, Leendert
Gerrit Westerink and, not least, in Germany with the works of Werner
Beierwaltes.



Lists of Proclus' works are available in the two supplements on 



> 
> Proclus' main extant works
> 


and



> 
> Proclus' complete works (extant, lost, and spurious).
>