## 1. Transmission



Arabic Philosophy was known in the Latin West through translations,
and, to a small degree, through personal contacts between Christians
and Muslims, as in the case of Frederick II Hohenstaufen, who was
directly acquainted with a number of Muslim scholars. A small number
of Christian scholars, such as Ramon Marti and
Ramon Llull, knew Arabic themselves and drew on Arabic sources
when composing Latin works. Translations, however, were far more
influential. The first Arabic-Latin translations to transport
philosophical material into Latin Europe were the translations of
texts on medicine and natural philosophy produced towards the end of
the eleventh century in Italy, most of them by the translator
Constantine the African, who, in contrast to later translators, tried
to disguise the Arabic origin of his texts (Burnett 2006,
22-24). In Spain, in the first half of the twelfth century,
several important astrological texts were translated, such as
Albumasar's *Great Introduction to Astrology*, which
incorporated much material of the Aristotelian tradition (Lemay
1962).



The translations of philosophical texts proper, such as by
al-Kindi, by the anonymous author of the *Liber de
causis*, by al-Farabi, Isaac Israeli,
al-Ghazali and Avicenna, but also of Greek works transmitted
in Arabic, assumed full pace in Toledo in the second half of the
twelfth century, where two very prolific translators worked: Gerard of
Cremona and Dominicus Gundisalvi. It is likely that
al-Farabi's treatise *Enumeration of the
Sciences*, translated twice, by Gerard and Gundisalvi, served as a
model for a coherent translation program. An indication of this is
that later Toledan translators such as Alfred of Shareshill, Michael
Scot and Hermannus Alemannus filled in gaps in
al-Farabi's list of disciplines which the earlier
translators had not covered (Burnett 2001). The translation movement
was also influenced by the philosophical preferences of Jewish
scholars. Gundisalvi worked together with the Jewish scholar Avendauth
when translating Avicenna's *De anima*, which Avendauth
had recommended for translation, and Gundisalvi's other
translations may also go back to such recommendations. The impressive
Spanish translation movement was motivated and fostered by several
factors: the personal interest of individual translators; the demand
for scientific texts by the French schools; the availability of Arabic
manuscripts in cities newly conquered by the Christians; the patronage
of the archbishop of Toledo; and by clerical interests in promoting
Latin scientific culture in an Arabic-speaking Christian environment
(Hasse 2006, 79-84).



The next important phase of the transmission were the translations
made in Sicily and southern Italy by several translators associated
with the Hohenstaufen or the papal court, the most productive of which
were the Averroes translators Michael Scot and William of Luna. It was
only about thirty years after Averroes' death in 1198 that Latin
Averroes translations became available in the newly developing
universities (Gauthier 1982b). In 1255, the statutes of the Parisian
arts faculty declared all known works of Aristotle mandatory reading
for the students - a very influential move, which much
contributed to the rise of Averroes' commentaries as the
principal secondary literature of Latin university culture.



After about 1300, Arabic-Latin translation activities ceased almost
entirely, to resume again after 1480. The Renaissance translations
were mostly produced by Italian Jews from Hebrew versions of Arabic
texts, an exception being Andrea Alpago's Avicenna translations
from Arabic, which were produced in Damascus (Tamani 1992; Burnett
1999; Hasse 2016, ch. 3). The social context of these translations was
the vibrant philosophical culture of Italian universities and
especially of Padua, and the patronage of Italian scholars belonging
to the Italian nobility, who had been educated in these universities. The impact of these Renaissance translations, which is
weaker than that of the medieval translations, remains largely
unexplored. It has aleady been shown that the new translations
influenced the logical and zoological discussions of the sixteenth
century (Perfetti 2000, 106-109; Perfetti 2004,
XVII-XVIII; Burnett 2013). In the second half of the sixteenth
century, interest in Arabic philosophy and sciences declined, and with
it the Arabic-(Hebrew-)Latin translation movement. At the same time,
the new academic study of Arabic culture developed, which was
motivated primarily by historical and philological, but not by
philosophical interests. From the seventeenth century onwards,
translations into vernacular languages gradually replaced Latin
translations from Arabic (Bobzin 1992).



The corpus of Arabic philosophical texts translated into Latin was
substantial: A recent publication lists 131 textual items (Burnett
2005; see Kischlat 2000, 53-54, 196-198 for manuscript
distribution; on Avicenna translations see Bertolacci 2011 and 2013b;
on translator attribution see Hasse & Buttner 2018). The
introduction of Arabic philosophy into Latin Europe led to the
transformation of almost all philosophical disciplines. The influence
is particularly dominant in natural philosophy, psychology and
metaphysics, but is also felt in logic and ethics. The Arabic impact
is particularly strong in the thirteenth century, but some Arabic
traditions, such as Averroes' intellect theory, reach the high
point of their influence in Latin Europe as late as around 1500 (The
influence of Jewish philosophers writing in Arabic, such as Ibn
Gabirol and Maimonides, is not covered in this article).


## 2. Division of the Sciences



Arabic divisions of the sciences influenced the Latin West mainly
through Dominicus Gundisalvi' treatise *Division of
Philosophy* (*De divisione philosophiae*). In this text,
Gundisalvi reuses much material from his own abbreviating translation
of al-Farabi's *Enumeration of the
Sciences* (*Ihsa`
al-'ulum*), of which a second, more literal translation
was produced by Gerard of Cremona. But it was Gundisalvi's own
Arabicized treatise which was the main channel of
al-Farabi's influence. The mostly anonymous
introductory literature for *artes* students of the thirteenth
century draws amply on Gundisalvi's treatise, sometimes
referring to Gundisalvi as "Alpharabius" (Lafleur 1988,
341n). The translator Michael Scot also writes his own Division of
philosophy, in which he adopts substantial material from Gundisalvi,
but arranges it according to his own scheme (Burnett 1997).



Gundisalvi adopts central principles for the division of the sciences
from Avicenna: that the principal criterion of division between the
sciences is their subject matter; that a science cannot demonstrate
the existence of its own subject matter; and that there are two kinds
of subordination of a science: either as a part (*pars*) of
another science, when it studies a part of its subject matter, or as a
species (*species*) of another science, when it studies the
subject matter in a specific respect (Hugonnard-Roche 1984;
Fidora & Werner 2007, 24-35).



Al-Farabi's influence is particularly obvious in
the enumeration of the seven parts of grammar, the eight parts of
natural science (covering the spectrum of Aristotle's *libri
naturales*), and the seven parts of mathematics: arithmetic,
music, geometry, optics, astrology, astronomy, the science of weights,
the science of technical devices (*ingenia*) (see the tables in
Bouyges 1923, 65-69). As to the discipline of logic, Gundisalvi
explicitly embraces al-Farabi's division into
eight parts, following the tradition which makes Aristotle's
*Rhetoric* and *Poetic* parts of logic. The Farabian
division of logic into eight parts reappears, for example, in Roger
Bacon (Maieru 1987) and in Arnoul de Provence's
*Division of the Sciences* (ca. 1250); Arnoul remarks that
neither Aristotle nor common usage includes *Rhetoric* and
*Poetic* among the parts of logic (Lafleur 1988, 342).
Gundisalvi further distinguishes with al-Farabi between
five kinds of syllogistic reasoning, of which demonstration is the
highest. Al-Farabi's emphasis on demonstration as
the pivotal means for the acquisition of certain knowledge is an
important innovation of Arabic philosophy, which reached the Latin
West via Gundisalvi (Fidora 2007).



The influence of al-Farabi's *Enumeration of
the Sciences* extends also to specific areas such as music (Farmer
1934, 31-34). In general, al-Farabi's and
Gundisalvi's works were instrumental in disseminating a
systematic division of the sciences which integrated the full range of
Aristotle's works and a broad spectrum of sciences, many of
which were new to the Latin West (Burnett 2011).


## 3. Logic



The Arabic influence in logic is thinner than in other disciplines
(apart from ethics), because only a few works of Arabic logic were
translated into Latin. The most influential translations were the
Isagoge part of Avicenna's summa *The Healing*
(*al-Shifa`*) and al-Ghazali's
*Intentions of the Philosophers*, the first part of which is a
reworking of Avicennian logic. Ramon Llull produced an Arabic
compendium of al-Ghazali's text, which he himself
translated into Latin (Lohr 1965). To these sources one may add
al-Farabi's *Enumeration of the Sciences*,
which transmitted much material on logical disciplines. Hermannus
Alemannus' translation of Averroes' commentary on the
*Poetics* was important because it remained the only source on
Aristotelian poetics available in the Middle Ages and had a rich
manuscript transmission (for its influence on Petrarch's
negative judgement about Arabic poetry see Burnett 1997). Other
translated texts remained largely uninfluential, such as William of
Luna's translations of five commentaries by Averroes on
Aristotle's logical works, or the Averroes translations made
from Hebrew in the Renaissance. In sum, this means that the Latin West
was not aware of the more innovative parts of Arabic logic, such as in
syllogistics and modal logic (Street 2005).



Several particular doctrines of Arabic logic, however, were very
influential. Among them was Avicenna's theory of the subject
matter of logic, with its related doctrine of first and second
intentions. Avicenna's basic claim is that logic deals with
second-order concepts. This is discussed in the logic part of *The
Healing*, but spelled out in technical vocabulary in the
metaphysics part (*Metaphysics* I,2): "The subject matter
of logic is the secondary intelligible concepts
(*al-ma'ani al-ma'qula
al-thaniyya*, *intentiones intellectae secundo*),
which depend on the primary intelligible concepts with respect to the
manner by which one arrives through them at the unknown from the
known". In this sentence, "concept"
(*ma'nan*) is rendered in Latin with the term
*intentio*.



A brief note on this term is at place: In Arabic-Latin translation
literature, *intentio* is very often used to render
*ma nan*, with the consequence that the term
*intentio* took on a similarly broad semantic range as its
Arabic counterpart. In the writings of Avicenna, *ma'nan*
may mean "concept", but also "meaning" of a
word, or something "intelligible" by the intellect, or
"perceptible" by estimation but not by the external senses
(on estimation see section 5.1). In Averroes' epistemology, the
term *ma'nan* has a specific meaning as the object of
memory and a broader meaning as the abstracted content of sensory,
imaginative or intelligible forms (Black 1996, 166).



In Avicenna's theory of logic, second intentions are defined as
the properties of concepts which these concepts acquire when used in
attaining knowledge, for example: being a subject or being a
predicate, being a premise or being a syllogism. Avicenna thus
confirms that logic has a proper subject matter, and hence becomes a
full-fledged part of philosophy, and not only a tool for the
philosophical disciplines (Sabra 1980, 752-753).
Avicenna's definition of logic appears already in Dominicus
Gundisalvi (*De divisione philosophiae* 150). Further Latin
writers to adopt Avicenna's thesis that the subject matter of
logic is second intentions are Roger Bacon and Thomas Aquinas,
followed by many subsequent authors such as Pseudo-Robert Kilwardby,
Radulphus Brito, Hervaeus Natalis, Peter Aureoli, Duns Scotus and
William of Ockham (Knudsen 1982; Maieru 1987; Perler 1994).



It was a matter of dispute how first and second intentions differ,
what they refer to and what their ontological status is, a dispute
bordering on epistemology and the philosophy of mind. Important
participants in this discussion are Roger Bacon, who defines
intentions as intelligible species, that is, mental likenesses of
things, and Hervaeus Natalis and Peter Aureoli, who (apart from
disagreeing on many issues) both hold that intentions are neither
identical with extramental things nor with qualities of the intellect;
they have their own "intentional being" (*esse
intentionale*), which is the result of a cognitive act (Perler
1994). This position was criticized both by nominalists and realists:
the nominalist William of Ockham objected against the reification of
intentions and held that intentions are always natural signs in the
mind; second intentions are natural signs which signify other natural
signs (*Summa logicae* I.12); the realist author Walter Burley
rejects the idea of a special being of intentions and argues that
second intentions are part of extramental reality (Knudsen 1982).
Logic as the science of second intentions continued to be a
philosophical topic well into the sixteenth century, especially among
Thomists and Scotist authors.


## 4. Natural Philosophy



Natural philosophy is the field with the greatest number of
Arabic-Latin translations. In this discipline, Arabic philosophers had
been particularly active, and Latin philosophers were particularly
interested. Arabic natural philosophy reached the Latin West earlier
than the other philosophical disciplines. The medical and astrological
translations of the late eleventh and early twelfth century
transported much philosophical material of the Graeco-Arabic tradition
to the Latin world. Under the influence of these Arabic sources, Latin
authors of the twelfth century explained natural phenomena by recourse
to the four elements, the four qualities, the four humours, the three
*spiritus* (natural, spiritual, animal) and their organs, the
localization of the soul's faculties in different cavities of
the brain, the distinction between the sublunar and the heavenly
universe, the circular movement of the heavenly spheres, and by using
Aristotelian concepts such as matter and form, action and passion,
cause and effect. While many Latin writers of the twelfth century
continued to understand nature in terms of the Latin Christian
tradition, others, in the context of the so-called "school of
Chartres", such as William of Conches, Adelard of Bath, Hermann
of Carinthia and Bernardus Silvestris, drew amply on the new medical
and astrological sources, often combining them with the doctrines of
Plato's *Timaeus* (Burnett 1982, introduction; cf. also
Lemay 1962). Sometimes they did this by openly dividing their
presentation into a section according to the church fathers and a
section according to the philosophers and natural scientists
(*physici*), which integrated material from the Latin and
Arabic philosophical traditions (e.g. the treatises
*Philosophia* by William of Conches and *De natura corporis
et animae* by William of St.-Thierry).



The influence of Arabic in natural philosophy in the later Middle
Ages, that is, after the translations of Avicenna and Averroes, is
particularly strong in psychology (section 5 below). But other
disciplines, such as physics, cosmology, meteorology, or zoology, are
also influenced by Arabic sources (see Mandosio 2018 on meteorology),
in particular by Averroes' commentaries and by his criticisms of
Avicenna (listed in Cerami 2018). Several theses from Averroes'
long commentaries on *Physics* and *De caelo* influenced
the history of medieval Latin physics and cosmology: the explanation
of projectile motion (e.g. of a thrown stone) as the successive motion
of the medium; the thesis that motion and time differ in reality, but
only with respect to the numbering soul; and the theory that the
heavenly sphere is in a place only accidentally, insofar as it moves
around the earth at its center (Maier 1951; Wood 2010; Trifogli 2000;
Trifogli 2010).



One issue on which Avicenna and Averroes disagreed was the "form
of bodiliness" (*sura jismiyya*, *forma
corporeitatis*), which, Avicenna argued, is the common form of
prime matter that underlies all individual bodily forms, whereas
Averroes denied that the "form of corporeality" is a form
in the category of substance; it is only an accident, to be identified
with indeterminate three-dimensionality (Hyman 1965). Thomas Aquinas
rejected the idea that prior to the intellective soul there exists a
substantial form in matter (*Summa theol.* Ia q. 76 a. 4, a.
6). The Avicennian concept was adopted by others, such as Henry of
Ghent and Duns Scotus, and thus served the theory of the plurality of
substantial forms. That prime matter has its own actuality became a
principle identifying the Franciscan party in the doctrinal struggles
with the Dominicans. The discussion of the concept of *forma
corporeitatis* continued well into the sixteenth century (Des
Chene 2000, 81-93).



Three prominent topics of natural philosophy are here singled out for
closer treatment: the eternity of the world, the persistence of
elements in a compound and spontaneous generation.


### 4.1 Eternity of the World



The Greek theory of the eternity of the world was a challenge to the
Christian world view, a challenge increased by the fact that the
theory was supported by Arabic sources: by Avicenna, who combined it
with a metaphysical concept of God as the "necessary being in
itself", which is the eternal efficient cause of the existence
of the heavenly and sublunar world (see section 6.4 on the first
cause), and by Averroes, who combined it with a conception of God as
the prime mover, whose existence is proved in natural philosophy. In
Giles of Rome' *Errors of the Philosophers*, Avicenna and
Averroes are accused of many "errors", but the eternity of
the world figures most prominently. Averroes, in particular, is
attacked for opposing "even more vehemently than did the
Philosopher (Aristotle) those who held that the world had had a
beginning" (Giles of Rome 1944, 15). The eternity of the world
and related theses were condemned as heretical in 1270 and 1277 by the
Parisian bishop Etienne Tempier (art. 87, 90, 99, 184)
(Piche 1999).



In the thirteenth century and beyond, the issue was widely discussed
by the scholastics, who arrived at a variety of positions, but
unanimously held that the world was created in time by God, which
means that they never fully shared Avicenna's or Averroes'
position. Many arguments of the scholastic discussion were drawn from
Arabic authorities, in particular from Averroes' long
commentaries on *De caelo* and *Physics* and from
Avicenna's *Metaphysics*. First traces of Arabic
influence can be found in Philip the Chancellor's *Summa de
bono* (dating 1225-8). Thomas of York, for instance, takes
over Averroes' exposition of the four principal views on the
issue (*Comm. magnum De caelo* I.102; Dales 1990, 81). Passages
drawn from Arabic texts were not only employed to defend, but also to
attack the eternity thesis. One particularly often quoted argument
comes from al-Ghazali's *Intentions of the
Philosophers*: If the world was eternal, an infinite number of
(immortal) souls would now exist, which is impossible (Dales 1990, 44,
256). Another very influential source of the Latin debate was
Maimonides' *Guide* *for* *the Perplexed*
(II.13-28); Maimonides argued that both eternity and
non-eternity are possible philosophically.



Thomas Aquinas' *Commentary on the Sentences* (II, d.1
q.1 a.5) is a good example of the impact of Arabic sources. Among the
arguments cited from Averroes in favour of eternity are that there is
always another moment in time before a moment in time; that only
motion can be the cause of a change from rest to motion; that if the
world had a beginning, a vacuum would precede the world (*Comm.
magnum De caelo* III.29, *Comm. magnum Phys.*
VIII.8,9,11,15). Avicenna is cited by Thomas as holding that
God's will is unchangeable and never starts anew (an argument
advanced also by Averroes), and that it is impossible that God
precedes the world in duration, because this implies that time existed
before the world and before movement (*Metaphysics* IX.1).
These arguments clearly influenced Thomas' conclusion that the
eternity thesis is the most probable in philosophical terms. However,
just like creation, eternity escapes full demonstration. From the
standpoint of faith, the eternity of the world is false and heretical.
In his treatise *On the Eternity of the World*, Thomas Aquinas,
in contrast to most of his contemporaries, defends the possibility of
an eternal creation, thus approaching the position of Avicenna and
other Neoplatonic thinkers.



Positions on the eternity of the world by some masters of arts were in
some cases very provocative. In the eyes of Siger of Brabant, the
natural philosopher cannot but conclude that the world is eternally
created, whereas the metaphysician concedes that God's will is
inscrutable and that hence there is no certainty about eternity or
non-eternity (*De aeternitate mundi; Quaest. in tertium De
anima* q.2). For Boethius of Dacia, the natural philosopher has to
infer the eternity of movement from the principles of natural
philosophy, but the metaphysician, even though he can demonstrate the
existence of a first cause, is unable to demonstrate whether the world
is coeternal with the first cause or non-eternal, given the
inscrutability of God's will (*De aeternitate mundi*).
Both authors share the conviction that the natural philosopher is
forced to conclude that the world is eternal, thus provoking
theological opposition. The arguments for this conclusion were largely
furnished by Arabic sources.


### 4.2 The Elements in a Compound



In the Latin West, Avicenna and Averroes were known as the principal
adversaries on a much-discussed question of element theory, especially
in the fourteenth century. Given that all physical substances (apart
from the elements themselves) are mixtures of elements, how do the
elements exist in them? (Maier 1952; Grant 1974, SS77, Eichner
2005, 139-145). Avicenna's answer is that the substantial
forms of the elements remain unaltered when a compound is formed; only
the qualities of the elements are altered and unite to a mean quality
*(qualitas media*), or complexion (*complexio*). The
complexion disposes the matter to receive the substantial form of the
compound from the active intellect, the giver of forms (*dator
formarum*) (*The Healing: Physics* I.10, *On
generation* 6). The problem with this position, as many
scholastics saw, is that several bodies are combined in one, which do
not form a true mixture. Averroes rejects Avicenna's theory and
argues that the substantial forms of the elements are diminished in
the compound (*Comm. magnum De caelo* III.67). The form of the
compound is "composed" of the elementary forms (*Comm.
magnum Metaph.* XII.22). In order not to violate Aristotle's
principle that substantial forms cannot be diminished or augmented (a
man is not more man than another), Averroes argued that elementary
forms are not substantial forms in the full sense.



A third influential alternative was proposed by Thomas Aquinas. Thomas
argued that the substantial forms of the elements are destroyed and
that only the qualities contribute to the mixture. Thomas shares
Avicenna's conviction that every form presupposes a certain
material disposition, which is the mean quality characteristic of the
compound. But he deviates from Avicenna in that the forms of the
elements are not preserved; they are only virtually present in the
compound, in that their powers survive (*De mixtione
elementorum*, cf. *Summa theol.* Ia q. 76 a. 4).
Thomas' position found many adherents. Its problem is that
physical bodies cannot truly be called mixtures of elements.



Avicenna's theory of the permanence of substantial forms was
often mentioned, but rarely accepted in the Latin West.
Averroes' position, that the elementary forms can be diminished
and augmented, found many supporters, among them Henry of Ghent,
Petrus Johannes Olivi, Richard of Middleton, John of Jandun and
several members of the Merton school of the fourteenth century (Maier
1952, 36-46). Many authors accept Averroes' position with
modifications, especially by reinterpreting the thesis of the
intension and remission of elementary forms. Henry Bate and Dietrich
of Freiberg argue that the diminished forms assume the character of
potential forms and thus join the matter of the compound; the form of
the compound is a form added to these diminished forms. For Averroes,
in contrast, the combination of the diminished forms was identical
with the new form of the compound. In the Renaissance, the issue
continued to be discussed. There was disagreement even among the
followers of Averroes. Some, as Marcantonio Zimara, held that the form
of the compound was added to the other forms, others, as Jacopo
Zabarella, argued against such addition (Maier 1952, 46-69).


### 4.3 Spontaneous Generation



Spontaneous generation, that is, the generation of life without their
being any parents, as when worms grow in decay, is a much discussed
issue of medieval physics and metaphysics. The conflicting
explanations of the phenomenon by Avicenna and Averroes much
determined the Latin discussion until the sixteenth century. While
Avicenna holds that spontaneous generation depends upon ever more
refined mixtures of elementary qualities which trigger the emanation
of forms from the active intellect, the giver of forms (*The
Healing: Meteorology* II.6: *On Floods*), Averroes explains
it with the influence of certain celestial constellations which
actualize potential forms in water or earth. Avicenna and Averroes
also disagree about the special case of the spontaneous generation of
human beings, which Avicenna finds possible, whereas Averroes does
not. For Averroes, all spontaneously created animals are not true, but
abnormal, monstrous animals (*Comm. magnum Metaph.* II.15,
VII.31, XII.13,18) (Bertolacci 2013a).



In the Latin West, Averroes' explanation dominated the
discussion for several centuries (Hasse 2007a). Thomas Aquinas argues that there is
no need to assume the existence of an Avicennian giver of forms to
explain spontaneous generation, since the celestial power suffices for
producing ordinary animals from matter. More complex beings, however,
such as horses and human beings, cannot be produced by the celestial
power alone without the formative power of the semen (*Quaest. de
potentia*, qu. 3 a. 8,9,11). Thomas' position was called the
*media via* by later authors, that is, the middle way between
Avicenna and Averroes, since Thomas rejected Avicenna's theory,
but also modified Averroes' position in treating spontaneous
generation as a natural, and not a miraculous phenomenon.



Averroes' theory of celestial influence and Thomas
Aquinas' *media via* became mainstream in the Latin
middle ages. A few authors, however, followed Avicenna in allowing for
the spontaneous generation of human beings, among them Albertus
Magnus, Blasius of Parma, and, in the Renaissance, Pietro Pomponazzi,
Paolo Ricci and Tiberio Russiliano. Pomponazzi makes the spontaneous
generation of human beings dependent upon the conjunction of the
superior planets Jupiter and Saturn, and thus introduces another
Arabic theory into the discussion: Albumasar's astrological
theory of the great conjunctions (Nardi 1965).



A modified version of Avicenna's theory of the giver of forms
appears in John Buridan, who deviates from the dominant position that
the form of human beings comes from without, i.e. from God, whereas
that of animals is educed from matter. In contrast, Buridan holds that
*all* forms are given by a separate incorporeal substance,
which he calls God. The phenomenon of spontaneous generation supports
this view, since it cannot be explained with the influence of the
stars, which is too weak and imperfect to generate animals (*In
Metaphysicen Aristotelis* lib. 8 q. 9). What does not appear in
Buridan, is Avicenna's theory of the subsequent mixtures of
elementary qualities.


## 5. Psychology



In Latin psychology, the influence of Arabic works is particularly
strong and lasted well into the sixteenth century. Avicenna and
Averroes, the most influential philosophers, presented the West with a
faculty psychology in the tradition of Aristotle and enriched by
Graeco-Arabic medical doctrines, such as about the cavities of the
brain, the nerves, and the spirits which transport information in the
body. From about 1220 onwards, the full range of Avicennian faculties
(vegetative, external and internal senses, the motive faculties,
practical and theoretical intellect) appears in Latin treatises by
masters of arts and theologians. This system of faculties remains, by
and large, standard for a long time in philosophical handbooks, from
the anonymous *Philosophy of the Simple* (*Philosophia
pauperum*) and Vincent of Beauvais' *Mirror of
Nature* (*Speculum naturale*) in the thirteenth century up
to the *Philosophic Pearl* (*Margarita philosophica*) of
the 1490s. Also influential was Avicenna's definition of the
soul as a separate substance (Hasse 2008) and his thought experiment of the
"Flying Man" (Hasse 2000, 80-92).



Averroes disagreed with Avicenna on a number of topics concerning
faculty psychology, for example: on the organ and medium of touch, on
the material or immaterial transmission of odors, and on whether human
beings have an estimative faculty or not. These controversies were
continued in the Latin tradition. The most influential pieces of
psychological doctrine imported from the Arabs probably were
Avicenna's theory of estimation (*wahm*), his theory of
potential, acquired and active intellects, and Averroes' thesis
that there is one intellect for all human beings.


### 5.1 Estimation



Avicenna had argued in his *On the Soul* (the *De anima*
part of *The Healing* I.5 and IV.3) that human beings and
animals share an internal sense called estimation (*wahm*,
*aestimatio*), which perceives so-called
"intentions" (*ma'anin*,
*intentiones*) in an object, such as hostility and
friendliness: The sheep perceives hostility in the wolf and judges
that the wolf is to be fled from. The basic ingredients of this theory
were adopted by many scholastic writers. There was disagreement,
however, over several issues: Firstly, Averroes and Thomas Aquinas (in
contrast to Avicenna, Albertus Magnus and others) argued that
estimation existed in animals only, but not in human beings. To
explain instinctive reactions in human beings, it is not necessary,
they argue, to assume the existence of a faculty besides the
cogitative faculty, or *ratio particularis*, as Thomas calls it
(*Summa theologiae* Ia 81.3c). Secondly, scholastic writers
were divided over whether the intentions are perceived in the object,
as Avicenna and Thomas Aquinas say (cf. also John Blund, *Tractatus
de anima*, ch. 19), or abstracted from sensory forms, as for
instance Albertus Magnus and John Buridan argue (Albertus, *De
anima* II.4.7; Buridan, *Quaestiones de anima* II.22)
(Black 2000; Hasse 2000, 141-153; cf. also Black 2011). Thirdly,
there was disagreement about the notion of "animal
judgement" propagated by Avicenna. Nominalists such as Adam
Wodeham argue that judgements always involve the formation of a
complex sentence, which presupposes linguistic capabilities; animals,
therefore, never truly judge (Perler 2006).


### 5.2 Active Intellect



Typical for Arabic intellect theory is the distinction between several
degrees or levels of intellect, from an entirely potential intellect
up to a perpetually active intellect, and the assumption, taken over
from later Greek philosophers, that the active intellect is an entity
separate from the human being. Al-Farabi, Avicenna and
Averroes identify the active intellect with the lowest of the
cosmological intelligences, and argue that the human intellect is able
to conjoin with the active intellect. The great majority of scholastic
writers teach that potential and active intellect are parts of the
soul, but there also existed a current adopting the Arabic idea of a
separate active intellect (e.g. Dominicus Gundisalvi and Petrus
Hispanus). Several scholastic authors identify the active intellect
with God on the authority of Avicenna and Augustine - a position
which modern scholars have labeled "Augustinisme
avicennisant" (Gilson 1926/27, 102). Among the earliest
exponents of the doctrine is Jean de la Rochelle, whose psychological
works were written in the 1230s. He teaches that the term
"active intellect" refers either to God or to the
angels' intellect or to the internal light of human beings,
depending upon which intellectual objects are grasped by the human
intellect (*Summa de anima* 116). This doctrine reappears in
the 1240s in the *Summa fratris Alexandri*, and in Vincent of
Beauvais. Later adherents are Roger Bacon, John Pecham, Roger Marston,
Vital du Four, and also Henry of Ghent (though only in parts of his
work). But other scholastics disagree. Adam of Buckfield, Bonaventure
and Thomas Aquinas criticize unnamed theologians for identifying the
active intellect with God. As philological evidence shows, they refer
to the above-mentioned current which begins with Jean de la
Rochelle. Thomas rejects the thesis because he interprets it in
illuminationist terms and finds it incompatible with his own
epistemology of abstraction (*Summa contra gentiles*
II.74). One should note, however, that Avicenna's epistemology
combines both abstractionist and emanationist aspects and that his
theory of abstraction also attracted Latin readers (Hasse 2001, but
cf. McGinnis 2007, and Black 2014).


### 5.3 The Four Intellects



Avicenna distinguishes four different states of the human intellect,
which are not different faculties of the soul, but different phases of
intellection: three potential intellects, called material, *in
habitu*, *in effectu*, and one actually thinking intellect,
the "acquired intellect" (*al-'aql
al-mustafad*, *intellectus adeptus*). The first
potential intellect is pure potentiality to know anything; the second
potential intellect knows axioms such as "The whole is bigger
than the part"; the third has already acquired conclusions
through syllogistic reasoning and the intuition of middle terms, but
does not consider them at the moment; the "acquired
intellect" comes about when the human intellect connects with
the active intellect (*De anima* I.5). This theory exerted a
profound influence on scholastic intellect theory, especially in the
period from Dominicus Gundisalvi to Albertus Magnus. The scholastics
inherited from Avicenna the principal idea that the activity of the
human intellect can be differentiated into different phases of gradual
development and into different acts of syllogistic reasoning (Hasse
2000, ch. II.6).



An important step in the reception of the doctrine is the anonymous
treatise *De anima et de potentiis eius* by a Parisian master
of arts of ca. 1225 (Gauthier 1982a, 53). This author adopts from
Avicenna the first three levels of intellect, the first being pure
potentiality, the second knowing first propositions, the third
conclusions, and combines it with teachings from Aristotle's
*Posterior Analytics* (I.3 and II.19) about the intellect
knowing axioms and principles. Jean de la Rochelle continues this line
and calls the second intellect *intellectus principiorum*, the
third *intellectus conclusionum*, and uses a Boethian term for
the axioms of the second intellect: "common notion of the
mind" (*communis animi conceptio)*, thus combining the
Avicennian doctrine with Latin axiomatic theory (*Tractatus de
divisione multiplici potentiarum animae* II.18).



In the writings of Albertus Magnus, the influence of Avicenna is
combined with that of Averroes, who distinguishes two intellects apart
from the separate active intellect: the material intellect, which is
pure potentiality (and unique, see section 5.4 below) and the
speculative intellect, which is the actuality of the grasped
intelligible. Averroes and Avicenna both teach that the human and
active intellect conjoin in the moment of intellection. Averroes, in
particular, claims that a perfect conjunction with the active
intellect results in God-like knowledge and that such a conjunction is
possible in this life (*Comm. magnum De anima* III.5 and
III.36).



Albertus Magnus, in his early *De homine* (qu. 56 a. 3), adopts
the Avicennian doctrine of three potential intellects in his
scholastic reformulation, but in his later works, under the influence
of Averroes, transforms it into a theory of intellectual ascension.
The highest level of the human intellect is called "acquired
intellect" (*intellectus adeptus*) and results from the
conjunction between the potential and the active intellect, both parts
of the human soul. In this stage, the intellect is able to grasp all
intellectual knowledge, and does not need to have recourse to the
senses again. In virtue of this intellect, a human being becomes
God-like (*De anima* 3.3.11) (de
Libera 2005, 325-327). Thomas Aquinas sharply disagrees. The
intellect can never dispense with the senses, since it needs the
phantasms for conceiving an intellectual form. This is why perfect
intellectual knowledge is not possible in this life (*Summa
theol.* Ia q. 84 a. 7).


### 5.4 Averroes' Unicity Thesis



Averroes' best known philosophical doctrine holds that there is
only one intellect for all human beings. The doctrine is sometimes
labelled "monopsychism", but this is a problematic term,
since Averroes' unicity thesis concerns the intellect, not the
soul. Averroes' theory has an epistemological and an ontological
purpose. On the one hand, Averroes wants to explain how universal
intelligibles can be known, on the other hand, he wants to account for
Aristotle's claim that the intellect is pure potentiality and
unmixed with the body (*Comm. magnum De anima* III.5). Many
scholastic readers were troubled by the problem of whether the
material (or potential) intellect, if it is one, can be the form of
the body. This problem was not directly addressed by Averroes himself,
but by many of his Latin partisans.



Modern scholarship is still divided about the significance of the
current of Averroism in the thirteenth century (for the more recent
discussion see Imbach 1991; Hayoun/de Libera 1991; Bianchi 1993;
Niewohner/Sturlese 1994; Kuksewicz 1997; Brenet 2003,
21-22; Coccia 2005, 20-53; Hasse 2007b; Martin 2007; Calma
2010, 11-20, 367-373; Martin 2013; Akasoy & Giglioni 2013).
It was argued, for instance, that the "radical
Aristotelians" of the thirteenth century were not
"Averroists" in a strict sense (Van Steenberghen 1974,
531-534). But that much is clear: there existed at least four
groups of authors who explicitly adopted the unicity thesis in one of
their writings: Siger of Brabant and possibly other masters of arts in
later thirteenth-century Paris; a second Parisian group in the early
fourteenth century around Thomas Wilton, John of Jandun and John
Baconthorpe; several Italian masters of arts at Bologna university in
the fourteenth century; and a larger group of authors in Renaissance
Italy and especially in Padua.



When the medievals used the Latin term *averroista*, they
referred to authors belonging to these groups. The term
*averroista* came into use in the later thirteenth century, but
on rare occasions. The first appearance, as we can see today, is in
Thomas Aquinas' treatise *On the Unicity of the
Intellect* (*De unitate intellectus*). The additional title
phrase *contra averroistas* appears only in the later
manuscript tradition and is unlikely to be authentic. It was in the
decades around 1500 that the term was used most frequently.
*Averroistae* were associated mainly with the unicity thesis,
but also with theories about the eternity of the world, God's
knowledge of the world, prime matter and happiness (Kuksewicz 1997,
93-96; Calma 2010). In the
Renaissance, *averroista* was also used, with a positive
connotation, to refer to experts on Averroes (Martin 2007; Martin
2013). A sensible historiographical usage of the term
"Averroism" should be tied to the medieval and Renaissance
usages. In particular, two senses of the term "Averroism"
seem historically legitimate: as meaning a current of followers of
Averroes who hold theologically controversional doctrines, or as
meaning a current of experts on Averroes. The first sense has a longer
tradition in the Middle Ages and in modern scholarship and is
therefore to be preferred generally. Some modern historians use the
term "Averroism" in a much broader sense for all
influences of Averroes' thought (e.g. Gauthier 1982,
334-335; Calma 2010, 368-369); so-called
"Averroisms" would then be found, for instance, in almost
all Latin Aristotle commentaries of the later Middle Ages. This usage,
however, ignores the historical roots of the meaning of the term.



Siger of Brabant (d. 1284) and John of Jandun (d. 1328) were the best
known and most influential Averroists. Siger, in his first and most
explicitly Averroistic work on the soul, argues that the separate and
eternal intellect is united to the body only in an operational union
and that the true form of the body is the sensitive soul (*Quaest.
in tertium de anima*, esp. q. 3 and 9). Under the influence of
Thomas Aquinas and others, Siger later revised his position. For John
of Jandun, the intellective soul, which in itself is one and separate,
operates within the body. It is united to the body only through the
assistance of the phantasmata (Brenet 2003). The Renaissance
Averroists Agostino Nifo and Luca Prassicio argued that Siger and John
of Jandun professed conflicting views: they interpreted Siger as
holding that the unique intellect can be united to the body as form
and John of Jandun that it cannot. Another influential Averroist was
John Baconthorpe (d. 1345/48): He developed the theory of the
so-called "double conjunction" (*copulatio
bifaria*) between intellect and bodily phantasms: one
epistemological, one ontological. The ontological conjunction
presupposes a union of unique intellect and human being in a way that
the intellect becomes a human faculty (Etzwiler 1971, 266-269).
Among the most explicit and outspoken Averroists of the Renaissance
were Nicoletto Vernia (d. 1499) and Luca Prassicio (d. 1533). The
unicity thesis was successful among Latin authors not only because
Averroes as *the* commentator had become an exceptional
authority of university education, but also because it was attractive
philosophically: it explained the possibility of the knowledge of
universals and it ensured that the intellective soul, as demanded by
Aristotle (*De anima* III.4, 429a22-25), was not mixed
with the body.



The unicity thesis was included among the doctrines condemned in 1270
and 1277 in Paris (art. 32) and in 1489 in Padua by the local bishops.
From a theological vantage point, its main drawback was its conflict
with the doctrine of individual immortality. The principal
philosophical counter-argument, first presented by Averroes himself
(*Comm. magnum De anima*, 393) and powerfully formulated by
Thomas Aquinas, was that the unicity thesis could not account for the
fact that "this individual man thinks", as Thomas puts it
("hic homo singularis intelligit", *De unitate
intellectus* III) (Black 2004). The standard reply by Averroes and
his followers was that the intelligible form is joined to the
individual human being through the actualized imaginative form, which
is particular. This way, individual knowledge of universal forms is
possible.



The decades around 1500 saw the high tide of the Averroist current, as
far as we can discern today (Schmitt 1979; Akasoy & Giglioni
2013). This is indicated by several pieces of evidence: the frequent
usage of the term *averroista*; the significant number of
authors who adopt the unicity thesis in one of their works; the
composition of super-commentaries on Averroes' commentaries;
and, finally, the fact that the correct interpretation of
Averroes' philosophical position became a matter of dispute
among his partisans (e.g. between Nifo, Trombetta, Zimara, Pomponazzi
and Prassicio). The unicity thesis lost its appeal as late as in the
middle of the sixteenth century, with the advent of new trends of
Aristotelianism that gave alternative explanations of universal
intellection (e.g. by Melanchthon, Zabarella and Suarez) (Hasse 2016,
ch. 5).


### 5.5 Naturalistic Theories of Prophecy



The philosophical interpretation of prophecy and miracles is a typical
feature of Arabic philosophy. The Latin West was not acquainted with
al-Farabi's concept of the philosopher-prophet,
the leader of the excellent city, but with parts of
al-Kindi's and Avicenna's theories. The general line
of Avicenna's naturalistic theory of prophecy, which describes
prophecy as resulting from extraordinary faculties of the soul, was
criticized by Thomas Aquinas. Thomas admits that there is also
"natural prophecy" which results from the contact of human
imagination and intellect with the celestial bodies and angels, but
"divine prophecy" is entirely dependent upon God, and not
upon the preparedness of the human soul (*Quaest. de veritate*,
q. 12, a. 1 and 3).



Among the specifics of prophecy theory, the working of miracles
received most attention in the Latin West. al-Kindi's and
Avicenna's explanation of miracles is naturalistic in the sense
that neither theory involves divine factors. al-Kindi argues in
*On Rays* (*De radiis*, extant only in Latin) that if a
person conceives a corporeal image in his imagination, the image
assumes a material existence in the *spiritus* that belongs to
the faculty. The *spiritus* in turn sends out rays, which alter
objects in the external world (d'Alverny & Hudry 1975,
230-1). An alternative to this extramission theory is formulated
by Avicenna, who claims that persons who have perfected their body and
soul are able to affect directly the external matter of the world and
may produce rain, fertile seasons, and the like - by sheer power
of the will. Avicenna arrives at this conclusion by generalizing the
principle that there are psychic causes for material effects (*De
anima* IV.4).



Albertus Magnus rejects Avicenna's long-distance theory because
it breaks with the Aristotelian rule that there is no efficient
causation without material contact (*De sensu et sensato*
1.10). Thomas Aquinas follows a third alternative: that psychic powers
can move the intervening medium, and so indirectly act on external
objects, which explains the damage caused by an evil eye. Thomas
borrows from a passage in Aristotle's *On Dreams*, in
which air is moved and affected by the eyes of menstruating women
(459b23-60a24). True miracles, however, are always produced by
God (*Summa theol.* Ia q.117 a. 3). In the later Middle Ages,
the Aristotelian theory of the movable medium proved more successful
than the extramission and action-at-a-distance theories of
al-Kindi and Avicenna. An exception is Roger Bacon, who teaches
that some persons are able to send out "powers, forms, and
heat" in order to alter bodies outside. Bacon employs
al-Kindi's theory of extramission in order to explain magic
as a purely natural phenomenon (in *De secretis operibus artis et
naturae*).



The high time for Arabic theories of miracles came in the Renaissance
(Hasse 2007c, 121-125). Marsilio Ficino in his *Platonic
Theology* (*Theologia platonica* XIII.4.8-9) explains
long-distance effects such as the evil eye with an extramission model
reminiscent of al-Kindi: The evil eye is explained with vapors
being emitted from the sorcerer's eyes which reach and afflict
the victim. True miracles, however, cannot be achieved without
God's assistence. Andrea Cattani (d. 1506) explicitly adopts
Avicenna's theory that noble souls are able to influence the
external world without mediation, but ties this extraordinary capacity
to inspiration by the Holy Ghost. Such reservations do not appear in
adoption of the theory by Pietro Bairo (d. 1558). Pietro Pomponazzi
(d. 1525) discusses Avicenna's position, but favours an
extramission theory: He explains a contemporary miracle in the town of
Aquila with the transmission of vapors which are issued from the eyes
of the observers (in *De naturalium effectuum causis sive de
incantationibus*, 237-8).


## 6. Metaphysics



The two most important Arabic sources of medieval Latin metaphysics
are the metaphysics part (*Ilahiyyat*) of
Avicenna's philosophical summa *The Healing*
(*al-Shifa`*), here referred to as his
*Metaphysics* (Hasse & Bertolacci 2012) and Averroes'
*Long Commentary on the Metaphysics* (Bertolacci 2009).
Avicenna's treatise presented metaphysics as a fully systematic
discipline and combined Aristotelian and Neoplatonic traditions.
Averroes' commentary proved an indispensable tool for
understanding Aristotle's text and offered an alternative to
Avicenna's position on several important issues.
Al-Ghazali's *Intentions of the Philosophers*
also contributed much to the dissemination of Avicennian metaphysics
in the Latin West (Minnema 2014; Minnema 2017). Another very
influential text was the *Discourse on the Pure Good (Kalam
fi mahd al-khayr*, *Liber de pura
bonitate)*, known in Latin also as *The Book of Causes (Liber
de causis)*. The anonymous Arabic author of the treatise
rearranged passages from Proclus' *Elements of Theology*
from a monotheistic, creationist and Plotinian perspective, and
combined them with doctrines from Plotinian and Aristotelian sources.
In 1255, the Latin text became part of the required curriculum of
study in the Faculty of Arts in Paris, together with the works of
Aristotle, with the effect that the text received many commentaries
and enjoyed an extraordinary transmission in more than 237 manuscripts
(Taylor 1983). The *Liber de causis* was long considered to be
an authentic text by Aristotle. When William of Moerbeke in 1268
translated Proclus' *Elements of Theology* into Latin,
Thomas Aquinas was able to identify Proclus as the main source of the
text. The *Liber de causis* remained popular, however. At least
74 commentaries from the twelfth to fifteenth centuries testify to its
great influence (d'Ancona Costa 1995, 195-258;
Fidora/Niederberger 2001, 205-247; Calma 2016, I,
20-21).


### 6.1 The Subject of Metaphysics



It was well known among the scholastics that Avicenna and Averroes
disagreed about the subject matter of metaphysics. In the two opening
chapters of his *Metaphysics*, Avicenna argues that no science
can demonstrate the existence of its proper subject, and that hence
God, whose existence is proven in metaphysics, cannot be its proper
subject. The subject (*mawdu', subiectum*) of
metaphysics is being as being. What is sought after
(*matlub*, *quaesitum*) in metaphysics, is
that which unconditionally accompanies being: such as the causes of
being, among which God is the first. Averroes countered that the
existence of the first principle cannot be demonstrated in
metaphysics, since such a proof can only begin with God's
effects and with movement in particular. This is why the proof of God
belongs to physics. The subject matter of metaphysics is separable
beings, among which counts God, as Averroes argues in the *Long
Commentary on the Physics* (ch. I.83, but in other works he
assigns this function to being as being; see Bertolacci 2007).



Most scholastic authors favoured Avicenna's position over
Averroes's, but within this mainstream position there was
disagreement about the manner in which God relates to the subject of
metaphysics, being as being. Albertus Magnus defends Avicenna against
Averroes' criticism. Being as being is the subject of
metaphysics, whereas the divisions and accidents (*passiones*)
of being are what is sought after, among them God and the separate
divine beings (*Metaph.* I.2, *Phys.* I.3.18). Thomas
Aquinas' position is again much influenced by Avicenna: The
subject of metaphysics is being as being (or *ens commune*),
whereas God is that which is aimed at in this science, insofar as he
is the cause of all being (*In Metaph.*, prooem.). But, other
than Avicenna, Thomas argues that God is the proper subject of a
different science, the principles of which are given in revelation:
theology (*Summa theol.* Ia q.1).



There were three principal positions on the issue in the Latin West
(Zimmermann 1998): Albertus and Thomas make God a subject of
metaphysics only as cause of the subject; a second group, among them
Roger Bacon and Giles of Rome, holds that God is one of several
subjects of metaphysics; a third group argues that God is part of the
subject of metaphysics. The latter position was influentially
formulated by Henry of Ghent (Pickave 2007), and taken up by
many other authors, among them Duns Scotus. Scotus develops his own
standpoint against the authorities of Avicenna, Averroes and Henry of
Ghent. He agrees with Avicenna that being as being is the subject and
that the notion of being includes all being, be it material or
immaterial. For Scotus, this notion of being explicitly includes God
within the subject of metaphysics (Zimmermann 1998,
294-329).


### 6.2 Primary Concepts



In chapter I.5 of his *Metaphysics*, Avicenna argues that just
as there are first and self-evident sentences, there are also
fundamental, first known, self-evident concepts, which are common to
all beings: "the existent", "the thing",
"the necessary". It was due to Avicenna that the
*primum cognitum*, the first object of knowledge became a
central topic of medieval Latin metaphysics. The question of the
*primum cognitum* was variously answered. For Guibert of
Tournai, Bonaventure and Henry of Ghent, God is the *primum
cognitum* (Goris 1999), for Thomas Aquinas and Duns Scotus being
(*ens*), for Berthold of Moosburg the good (*bonum*). An
example of a *primum cognitum* theory influenced by Avicenna is
Thomas Aquinas'. There cannot be an infinite regress, neither in
the order of demonstration, nor in the order of definition, Thomas
argues. This is why there is a first concept: "being". It
is what is first grasped by the mind, and it is unrestrictedly
universal. It is specific for Thomas, however, that the order of
definition and of demonstration are not on the same level. The
principle of contradiction rests (*fundatur*) on a conceptual
basis, since it can be reduced to the terms out of which it is
composed, among which "being" is the first (*In
Metaph.* IV.6; Aertsen 1996, 146-151).



Avicenna's theory of primary concepts was an important source
for the theory of transcendental concepts, which scholastic
philosophers developed in the thirteenth century, taking their cue
from Aristotle, Avicenna and the Dionysian tradition (Aertsen 2008;
Aertsen 2012; Pini 2012). Avicenna bequeathed to the discussion of the
transcendentals not only specific teachings about the notions
"being", "one" and "thing", but
also the general idea that, ontologically, the primary concepts are
most common since they are true of everything, and that,
epistemologically, they are first known since they are self-evident
and not reducable to prior concepts.


### 6.3 Essence and Existence, Universals and Individuals



Among the most influential philosophical doctrines of Arabic origin is
the distinction between essence (*mahiyya*,
*essentia*) and existence (*wujud*, *ens*),
which the Latin West got to know from Avicenna's
*Metaphysics*, chapters I.5 and V.1-2. The distinction
was very influential historically: it found adherents among
philosophers and theologians of the Arabic, Hebrew and Latin
cultures. The essence-existence distinction was used by Avicenna in
several metaphysical contexts, i.e., in the discussion of primary
concepts, of universals and of the first cause. The following
presentation focuses on the context of universals. Avicenna's
core idea was to differentiate between two components of universals:
essence and universality. The essence of "horseness", to
use Avicenna's example (*Metaphysics* V.1), is in itself
neither universal nor particular. Only existence, which in itself is
distinct from essence, adds universality or particularity, depending
upon whether "horseness" exists in the mind, that is, as a
universal, or in the exernal world, that is, as a particular. In some
of his writings, Avicenna emphasizes that there is universality only
if the essence is found in several objects in the external world
(Marmura 1979, 49).



Thomas Aquinas adopts Avicenna's distinction already in his
early *On Being and Essence* (*De ente et essentia* IV).
Essence can be considered either in itself or with respect to its
existence in the soul or in the particular things. Universality and
particularity are accidents of essence, which in itself is neither
universal nor particular. Thomas Aquins adopts the expression
"accidents of essence" from Averroes (*Comm. magnum
Metaph.* IV.3). The universal, according to Thomas, is a
*natura communis*, which has existence only in the intellect.
Individuals are essences individuated by matter with quantitative
dimensions, but only at the time of their origin; later individuation
is due to the form. In later writings, Thomas develops his concept of
essence and existence so that existence is that which actualizes
essence (*Summa theol.* Ia q. 3 a. 4) (Wippel 1990; Black
1999).



An influential defender of the real distinction between essence and
existence was Giles of Rome. Since he uses the terminology of
"thing" (*res*) for both concepts, he was
criticized for turning "existence" into a thing, which
itself exists only if another thing "existence" is added,
and so on ad infinitum. This argument was voiced against the real
distinction by Siger of Brabant and Godfrey of Fontaines (Wippel
1982), but it originally comes from Averroes, who flatly rejects
Avicenna's distinction in his *Long Commentary on the
Metaphysics* (IV.3).



While some authors take the extreme position that there is only a
mental distinction between essence and existence, Henry of Ghent
develops a modified version of Avicenna's theory. He
distinguishes between essence in itself and as existing, that is,
existing in the mind or in the external world. But he attributes a
specific kind of existence to the essence in itself
(*Quodlibet* I, 9 and III, 9): *esse essentiae*
("essential being"), which is the essence's eternal
relation to God as its cause. The *esse existentiae*, in
contrast, is the essence's actual existence. Henry thus develops
a theory of how essences exist prior to their actual existence in the
mind or in the world, enlarging on a brief and tentative reference in
Avicenna's *Metaphysics* I.5 to the "proper
existence" (*esse proprium*) of the essences.



Duns Scotus is also inspired by the Avicennian idea that the common
nature (*natura communis*), as Scotus calls it, is neither
truly universal nor truly particular in itself and that it is
universal only as an object of the intellect. But Scotus'
account of individuation differs: The common nature is particular only
because of a second "reality" in the object, a principle
of individuation or contracting difference, which by later authors was
called *haecceitas* ("thisness"). The distinction
between the two "realities" nature and thisness is not
real, but formal in the sense that the two are different, but never
exist apart from each other (*Ordinatio* II, d. 3, p. 1, q.
6).



The influence of Arabic metaphysics is much more extensive than these
brief references to a few well-known thinkers suggest. The influence
of Avicenna and Averroes, especially on the subject of metaphysics and
on essence and existence, extends to many authors and over many
centuries, up to sixteenth-century Jesuit authors such as Benedictus
Pereira, Pedro da Fonseca and Francisco Suarez (Leinsle 1985,
ch. 2)


### 6.4 The First Cause and the Emanation of the Intelligences



The influence of Avicenna's concept of the first cause as the
only necessary being in itself (*wajib al-wujud
bi-datihi*, *necesse esse per se*) and of
his theory of emanation is apparent already in the twelfth century.
Dominicus Gundisalvi, the Avicenna translator, distinguishes in his
*Procession of the World* (*De processione mundi*)
between the first cause, which is the "necessary being"
(*necesse esse*), and the created beings, which in themselves
are only possible beings. The entire universe proceeds from the first
cause. The principles first created, however, are not the
intelligences, as in Avicenna's metaphysics, but the material
and formal principles of the things (Jolivet 1988, 138-140;
Polloni 2017, 532-538).



The anonymous author of *The Book of First and Second Causes (Liber
de causis primis et secundis)*, which dates from the turn of the
thirteenth century, does not adopt the distinction between necessary
and possible beings, but describes the process of emanation in
strongly Avicennian terms: From the first cause issues a first created
being, an intellect. From this intellect, in turn, emanates a series
of intelligences, the lowest of which is the active intellect.
Emanation happens in triads: From an intelligence emanates, in virtue
of its intellectual activity, the form of a celestial sphere, the body
of a sphere, and another intelligence (ch. 4). The anonymous author
also draws on the *Book of Causes* (see the beginning of
section 6 above), for instance when describing the hierarchy of
intelligences as a decrease in power and unity (ch. 6).



William of Auvergne (d. 1249) is much attracted by Arabic metaphysical
and pyschological theories (which he often indiscriminately attributes
to "Aristotle and his followers") and discusses them at
length, but often rejects them in the end as conflicting with
Christian faith. In *On the Universe* (*De universo*
II.1), William discusses and rejects the Avicennian emanation system:
the necessity of causation through the first cause; the emanation of
the intelligences from the first intelligence down to the active
intellect; the active intellect as the efficient cause of human souls.
He nevertheless tacitly adopts the metaphysical principle "From
one arises only one" (*de uno non nisi unum*) from
Avicenna (Teske 1993), in particular within the context of Trinitarian
theology (Fischer 2015), and describes the first cause as the
"being necessary through itself" (Teske 2002, Fischer
2018).



Thomas Aquinas adopts from Avicenna the description of God as the
necessary being, whose essence is its own existence (*Summa contra
gentiles* I.22). Avicenna's influence is also apparent in a
well-known passage: the "five ways" (*quinque
viae*) of proving God's existence in the *Summa
theologiae* (Ia q. 2 a. 3). The third proof advances via
"the possible and the necessary": It establishes the
existence of something necessary in virtue of itself. The proof is
much coloured by Avicennian metaphysics, but its direct source is
Maimonides' *Guide for the Perplexed* (II.1), from which
it deviates only in minor respects. A conspicuous element of
Maimonides' and Thomas' proof is the premise, not
explicitly formulated by Avicenna, that, in an eternal world, every
possibility is eventually realized, which is a version of the
so-called "principle of plenitude" (Davidson 1987,
378-388). Thomas, however, rejects the Avicennian theory of
emanation. The creation of the world is not a necessary process, and
it does not occur through intermediaries, that is, intelligences or
angels. He also rejects Avicenna's theory of a separate active
intellect as the giver of the forms of the sublunar world and as the
ontological place of the intelligibles, a theory against which Thomas
advances epistemological arguments in the first place (*Summa
contra gentiles* II.42 and II.76). Albertus Magnus, in contrast,
tacitly adopts much of the *dator formarum* theory in several
of his writings, even though he often voices his criticism of it
(Hasse 2012).



The attraction of Avicenna's position is evident in the work of
Siger of Brabant. In some of his writings, Siger teaches that God as
the first being creates only one being immediately, the first
immaterial substance, from which emanate the other intelligences, the
celestial spheres and finally the sublunar world, in an eternal and
necessary process. The necessity is not universal, however, but finds
its limits in the contingency and in the free will which exists in the
sublunar world (*De necessitate et contingentia causarum*; Van
Steenberghen 1991, 346). Duns Scotus, in contrast, is very critical of
Avicenna's theory of necessary causation through the first
cause. He advances several reasons against it, the most important
being that there can only be contingency in the world if the first
cause does not act by necessity (*Ordinatio* I d. 8 p. 2 q.
un).



Several theses on the first cause and the intelligences which are
inspired by Avicenna are condemned by the Parisian bishop in 1277,
among them: that God is the first necessary cause of the first
intelligence and of the celestial movements (art. 58 and 59), that God
does necessarily what is immediately produced by him (art. 53), that
the active intellect is a substance separate from the human intellect
(art. 123), that the rational souls are created by the intelligences
(art. 30). Avicenna's theory of the first cause nevertheless
continued to influence the scholastic discussion. This is true, for
instance, of the proof for the existence of God, which had been cited
by Thomas Aquinas. Peter of Auvergne, Henry of Ghent and Duns Scotus
too draw on Avicenna's argument from the possible and necessary
being (Druart 2002; Janssens 2003; Pickave 2007, ch. 6).



The 1270 and 1277 condemnations were also directed against another
theory based on Arabic sources: astrological determinism (art. 143,
161, 167, 195, 206, 207). The condemnations do not testify to the
influence of Arabic philosophers proper: Avicenna was critical of
astrology for epistemological reasons and Averroes embedded
astrological doctrines in Peripatetic mainstream theories about the
influence of the stars. Rather, the condemnations indicate that Arabic
astrologers such as Albumasar and Alcabitius were very influential in
the Latin West already in the thireenth century.


## 7. Ethics



The influence of Arabic ethical and political writings is thin, partly
because Arabic philosophers were less productive in these fields, and
partly because important works were not translated at all (such as
al-Farabi's *Principles of the Citizens of the
Perfect State*) or as late as in the sixteenth century (such as
Averroes' *Commentary on Plato's Republic*).
Nevertheless, Arabic philosophers, via their teaching on the
intellect, exerted an important influence on the border area between
ethics and psychology, and on the discussion of human happiness in
particular.



Al-Farabi, Avicenna and Averroes share the view that
happiness is reached through the conjunction of the human intellect
with the separate active intellect. They also share an epistemological
optimism that for specifically gifted people, which they described as
philosophers or philosopher-prophets, a perfect conjunction is
possible in this life. Albertus Magnus's theory of happiness is
much influenced by these Arabic theories. As was mentioned above, he
adopted from Avicenna and Averroes the concept of an "acquired
intellect" (*intellectus adeptus*) as the highest level
of conjunction between possible and active intellect. Only in this
stage, a human being truly becomes a human being. Through the
conjunction with the active intellect the human intellect contemplates
the separate substances, and in this consists the "theoretical
happiness" of man (*felicitas contemplativa)*, a
happiness which is possible in this life (*De anima* III.3.12)
(Muller 2006; on Albertus' influence see de Libera 2005,
329-361). Thomas Aquinas disagrees with the epistemological
premisses and the ethical conclusion of this position: Since human
knowledge is bound to the senses, knowledge of the immaterial
substances is not possible in this life, and neither is perfect human
happiness (*Summa theol.* Ia IIae q.3 a.2). But Thomas, when
explaining beatific vision and human happiness in the afterlife,
adopts from Averroes the idea that a separate substance is conjoined
with the human intellect as its form (*Comm. on the Sentences*
IV, d.49 q.2 a.1; see Taylor 2012)



In 1277, several philosophical theses concerning human happiness and
the good life were condemned: that happiness is to be had in this life
and not in another (art. 176), that there is no better state (of life)
than studying philosophy (art. 40). These articles were apparently
directed at masters of arts at the university of Paris, among them
Siger of Brabant and Boethius of Dacia. As we know from fragments of
Siger's treatise *On Happiness* (*De felicitate)*,
he embraces Averroes' thesis that all intellects are made
blessed through the conjunction with the active intellect. In
Siger's interpretation, human beings in such a state think God
by an intellection which is God himself. There are many indications
that Siger was convinced that the knowledge of the separate substances
and thus the attaining of human happiness is possible in this life
(Steel 2001, 227-231). Boethius of Dacia is also convinced that
human happiness can be reached in this life, which is a happiness
proportioned to human capacities, whereas the highest kind of
happiness as such is reserved to the afterlife (in his treatise *De
summo bono)*. Boethius appears to be inspired by Arabic theories
of intellectual ascension, but does not endorse a theory of
conjunction, as does Siger. His conviction that the
philosopher's life is the only true life echoes the very
self-confident and elitist stance taken by the major Arabic
philosophers.