Medieval philosophy

St. Augustine

During these centuries philosophy was heavily influenced by Neoplatonism; Stoicism—the Hellenistic school of thought founded by Zeno of Citium (c. 335–263 bce)—and Aristotelianism played only a minor role. Augustine was awakened to the philosophical life by reading works of the Roman statesman Cicero (106–43 bce), but the Neoplatonists most decisively shaped his philosophical methods and ideas. To them he owed his conviction that beyond the world of the senses there is a spiritual, eternal realm of Truth that is the object of the human mind and the goal of all human striving. This Truth he identified with the God of Christianity. Human beings encounter this divine world not through the senses but through the mind—and, above the mind, through the intelligible light. Augustine’s demonstration of the existence of God coincides with his proof of the existence of necessary, immutable Truth. He considered the truths of both mathematics and ethics to be necessary, immutable, and eternal. These truths cannot come from the world of contingent, mutable, and temporal things, nor from the mind itself, which is also contingent, mutable, and temporal. They are due to the illuminating presence in the human mind of eternal and immutable Truth, or God. Any doubt that humans may know the Truth with certainty was dispelled for Augustine by the certitude that, even if they are deceived in many cases, they cannot doubt that they exist, know, and love.

Augustine conceived of human beings as composites of two substances, body and soul, of which the soul is by far the superior (see mind-body dualism). The body, nevertheless, is not to be excluded from human nature, and its eventual resurrection from the dead is assured by Christian faith. The soul’s immortality is proved by its possession of eternal and unchangeable Truth.

Augustine’s Confessions (c. 400) and De Trinitate (400–416; On the Trinity) abound with penetrating psychological analyses of knowledge, perception, memory, and love. His De civitate Dei (413–426; The City of God) presents the whole drama of human history as a progressive movement of humankind, redeemed by God, to its final repose in its Creator.

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Boethius

One of the most important channels by which Greek philosophy was transmitted to the Middle Ages was Boethius. He began to translate into Latin all the philosophical works of the Greeks, but his project was cut short by his imprisonment and execution by order of Theodoric, king of the Ostrogoths and the ruler of Italy from 493 ce. Boethius finished translating only the logical writings of the Syrian Neoplatonist philosopher Porphyry (c. 234–c. 305) and Aristotle. These translations and his commentaries on them brought to the thinkers of the Middle Ages the rudiments of Aristotelian logic. They also raised important philosophical questions, such as those concerning the nature of universals (terms or entities used to explain what it is for things to share a certain feature, attribute, or quality). Do universals exist independently, or are they only mental concepts? If they exist independently, are they corporeal or incorporeal? If incorporeal, do they exist in the sensible world or apart from it? Medieval philosophers debated at length these and other problems relating to universals. In his logical works, Boethius presents the Aristotelian doctrine of universals: that they are only mental abstractions. In his De consolatione philosophiae (c. 525; Consolation of Philosophy), however, he adopts the Platonic notion that they are innate ideas, and their origin is in the remembering of knowledge from a previous existence. This book was extremely popular and influential in the Middle Ages. It contains not only a Platonic view of knowledge and reality but also a lively treatment of providence, divine foreknowledge, chance, fate, and human happiness.

Church Fathers and Erigena

Another stream from which Greek philosophy, especially Neoplatonic thought, flowed into the Middle Ages was patristic literature, or the writings of the Fathers of the Christian church (the bishops and other teachers who expounded the orthodox Christian faith in the early centuries of the religion), notably including Origen (c. 185–c. 254), St. Gregory of Nyssa (c. 335–c. 394), Nemesius of Emesa (flourished 4th century), Pseudo-Dionysius the Areopagite (flourished c. 500), and St. Maximus the Confessor (c. 580–662). In the 9th century John Scotus Erigena (810–c. 877), a master at the Carolingian court of Charles II the Bald (823–877), translated into Latin some of the writings of these theologians, and his own major work, De divisione naturae (862–866; On the Division of Nature), is a vast synthesis of Christian thought organized along Neoplatonic lines. For Scotus, God is the primal unity, unknowable and unnameable in himself, from which the multiplicity of creatures flows. He so far transcends his creatures that he is most appropriately called superreal and supergood. Creation is the process of division whereby the many derive from the One. The One descends into the manifold of creation and reveals himself in it. By the reverse process, the multiplicity of creatures will return to their unitary source at the end of time, when everything will be absorbed in God.

St. Anselm

Although the Carolingian dynasty collapsed in the 10th century and intellectual speculation was at a low ebb in western Europe, signs of revival appeared almost contemporaneously. Political stability was achieved by Otto I (912–73), and Benedictine monasteries were revitalized by reform movements begun at Cluny and Gorze. In the next century, reformers such as St. Peter Damian combined the ascetic and monastic traditions and laid the foundation for the vita apostolica (“apostolic life”). Like the Christian writer Tertullian (c. 155/160–after 220), Damian mistrusted secular learning and philosophy as harmful to the faith. Other monks showed a keen interest in dialectic and philosophy. Among the latter was Anselm (1033/34–1109), an Italian theologian and philosopher who became abbot of the French monastery of Bec and later archbishop of Canterbury (1093).

Like Augustine, Anselm used both faith and reason in his search for truth. Faith comes first, in his view, but reason should follow, giving reasons for what human beings believe. Anselm’s monks asked him to write a model meditation on God in which everything would be proved by reason and nothing on the authority of Scripture. He replied with his Monologion (1077; “Monologue”). It contains three proofs of the existence of God, all of which are based on Neoplatonic thought. The first proof moves from the awareness of a multiplicity of good things to the recognition that they all share or participate more or less in one and the same Good, which is supremely good in itself, and this is God. The second and third proofs are similar, moving from an awareness of a multiplicity of beings that are more or less perfect to the recognition of that through which everything exists, which itself is supremely perfect.

Anselm’s later work, the Proslogion (1077/78; “Address” or “Allocution”), contains his most famous proof of the existence of God. It begins with a datum of faith: humans believe God to be the being than which none greater can be conceived. Some say there is no God, but even a fool, on hearing these words, understands them, and what he understands exists in his intellect, even though he does not grant that such a being exists in reality. But it is greater to exist in reality and in the understanding than to exist in the understanding alone. Therefore, it is contradictory to hold that God exists only in the intellect, for then the being than which none greater can be conceived is one than which a greater can be conceived—namely, one that exists both in reality and in the understanding. Philosophers still debate the meaning and value of this so-called ontological argument for God’s existence.

Bernard de Clairvaux and Abelard

Anselm’s inquiry into the existence and nature of God, as also his discussions of truth, love, and human liberty, aimed at fostering monastic contemplation. Other monks, such as the Cistercian St. Bernard de Clairvaux (1090–1153), were suspicious of the use of secular learning and philosophy in matters of faith. Bernard complained of the excessive indulgence in dialectic displayed by contemporaries such as Peter Abelard (1079–1142). He himself developed a doctrine of mystical love, the influence of which lasted for centuries.

The monks of the Parisian abbey of Saint-Victor were no less intent on fostering mystical contemplation, but they cultivated the liberal arts and philosophy as a means of furthering that goal. In this spirit, Hugh of Saint-Victor (1096–1141) wrote his Didascalicon (c. 1127; “Teaching”), a monumental treatise on the theoretical and practical sciences and on the seven liberal arts—the trivium (grammar, rhetoric, dialectic) and the quadrivium (arithmetic, music, geometry, astronomy). During the same period the School of Chartres, attached to the famous Chartres Cathedral near Paris, was the focus of Christian Neoplatonism and humanism.

Urban development in the 12th century shifted the centre of learning and education from monasteries to towns. Abelard founded and taught in several urban schools near Paris. A passionate logician, he pioneered a method in theology that contributed to later Scholasticism. His Sic et non (1115–17; Yes and No) cites the best authorities on both sides of theological questions in order to reach a correct solution. In philosophy his main interest was logic. On the question of universals, he agreed with neither the nominalists nor the realists of his day. His nominalist teacher Roscelin (c. 1050–c. 1125) held that universals, such “human” and “animal,” are nothing but words, or names. Abelard argued that this view does not take into account the fact that names have meaning. His realist teacher William of Champeaux (c. 1070–1121) taught that universals are realities apart from the mind. For Abelard, only individuals are real; universals are names or mental concepts, but they have meaning because they refer to individuals. They do not signify an essence common to individuals, as the realists maintained (e.g., the essence “humanity” shared by all human beings), but signify instead the individuals in their common condition, or status, of being in a certain species, which results from God having created them according to the same divine idea.

Islamic thought

Among the works to be translated from Arabic were some of the writings of Avicenna (980–1037). This Islamic philosopher had an extraordinary impact on the course of Scholasticism. His interpretation of Aristotle’s notion of metaphysics as the science of ens qua ens (Latin: “being as being”); his analysis of many metaphysical terms, such as being, essence, and existence; and his metaphysical proof of the existence of God were often quoted, with approval or disapproval, in Christian circles. Also influential were his psychology, logic, and natural philosophy. His Al-Qānūn fī al-ṭibb (Canon of Medicine) was authoritative on the subject until modern times. The Maqāṣid al-falāsifah (1094; “The Aims of the Philosophers”) of the Islamic theologian al-Ghazālī (1058–1111; referred to in Latin as Algazel), an exposition of Avicenna’s philosophy written in order to criticize it, was read as a complement to Avicenna’s works. The anonymous Liber de causis (“Book of Causes”) was also translated into Latin from Arabic. This work, excerpted from Proclus’s Stiocheiōsis theologikē (Elements of Theology), was often ascribed to Aristotle, and it gave a Neoplatonic cast to his philosophy until its true origin was discovered by St. Thomas Aquinas (c. 1224–74.

The commentaries of the Islamic philosopher Averroës (1126–98) were translated along with Aristotle’s works. As Aristotle was called “the Philosopher” by medieval philosophers, Averroës was dubbed “the Commentator.” The Scholastics often attacked Averroës as the archenemy of Christianity for his rationalism and his doctrine of the eternity of the world and the unity of the intellect for all human beings—i.e., the doctrine that intellect is a single, undifferentiated form with which individuals become reunited at death. This was anathema to the Christian Scholastics because it contravened the Christian doctrine of individual immortality.

Jewish thought

Of considerably less influence on the Scholastics was medieval Jewish thought. Ibn Gabirol (c. 1022–c. 1058), known to the Scholastics as Avicebron or Avencebrol, was thought to be an Arab or a Christian, though in fact he was a Spanish Jew. His chief philosophical work, written in Arabic and preserved in toto only in a Latin translation titled Fons vitae (c. 1050; The Fountain of Life), stresses the unity and simplicity of God. All creatures are composed of form and matter, either the gross corporeal matter of the sensible world or the spiritual matter of angels and human souls. Some of the Scholastics were attracted to the notion of spiritual matter and also to Ibn Gabirol’s analysis of a plurality of forms in creatures, according to which every corporeal being receives a variety of forms by which it is given its place in the hierarchy of being—for example, a dog has the forms of a corporeal thing, a living thing, an animal, and a dog.

Moses Maimonides (1135–1204), or Moses ben Maimon, was known to Christians of the Middle Ages as Rabbi Moses. His Dalālat al-hāʾirīn (c. 1190; The Guide for the Perplexed) helped them to reconcile Greek philosophy with revealed religion. For Maimonides there could be no conflict between reason and faith because both come from God; an apparent contradiction is due to a misinterpretation of either the Bible or the philosophers. Thus, he showed that creation is reconcilable with philosophical principles and that the Aristotelian arguments for an eternal world are not conclusive because they ignore the omnipotence of God, who can create a world of either finite or infinite duration.

Robert Grosseteste and Roger Bacon

The newly translated Greek and Arabic treatises had an immediate effect on the University of Oxford. Its first chancellor, Robert Grosseteste (c. 1175–1253), commented on some of Aristotle’s works and translated Aristotle’s Nicomachean Ethics from Greek to Latin. He was deeply interested in scientific method, which he described as both inductive and deductive. By the observation of individual events in nature, human beings advance to a general law, called a “universal experimental principle,” which accounts for these events. Experimentation either verifies or falsifies a theory by testing its empirical consequences. For Grosseteste, the study of nature is impossible without mathematics. He cultivated the science of optics (perspectiva), which measures the behaviour of light by mathematical means. His studies of the rainbow and comets employ both observation and mathematics. His treatise De luce (1215–20; On Light) presents light as the basic form of all things and God as the primal, uncreated light.

Grosseteste’s pupil Roger Bacon (c. 1220–92) made the mathematical and experimental methods the key to natural science. The term experimental science was popularized in the West through his writings. For him, human beings acquire knowledge through reasoning and experience, but without the latter there can be no certitude. Humans gain experience through the senses and also through an interior divine illumination that culminates in mystical experience. Bacon was critical of the methods of Parisian theologians such as St. Albertus Magnus (c. 1200–80) and Aquinas. He strove to create a universal wisdom embracing all the sciences and organized by theology. He also proposed the formation of a single worldwide society, or “Christian republic,” that would unite all humankind under the leadership of the pope.

William of Auvergne

At the University of Paris, William of Auvergne (c. 1180–1249) was one of the first to feel the impact of the philosophies of Aristotle and Avicenna. As a teacher and then as bishop of Paris, he was concerned with the threat to the Christian faith supposedly posed by pagan and Islamic thought. He opposed the Aristotelian doctrine of the eternity of the world as contrary to the Christian notion of creation. His critique of Avicenna emphasized the latter’s conception of God and creation. Against the God of Avicenna, who creates the universe eternally and necessarily through the mediation of 10 intelligences, William defended the Christian notion of a God who creates the world freely and directly. Creatures are radically contingent and dependent on God’s creative will. Unlike God, they do not exist necessarily; indeed, their existence is distinct from their essence and accidental to it. God has no essence distinct from his existence; he is pure existence. In stressing the essential instability and temporality of the world, William attributed true existence and causality to God alone. Although a follower of St. Augustine, William, like others of his time, was compelled to rethink the older Augustinian notions in terms of the newer Aristotelian and Avicennian philosophies.

St. Bonaventure

The Franciscan friar St. Bonaventure (c. 1217–74) reacted similarly to the growing popularity of Aristotle and his Islamic commentators. He admired Aristotle as a natural scientist, but he preferred Plato and Plotinus, and above all St. Augustine, as metaphysicians. His main criticism of Aristotle and his followers was that they denied the existence of divine ideas. As a result, Aristotle was ignorant of exemplarism (God’s creation of the world according to ideas in his mind) and also of divine providence and government of the world. This involved Aristotle in a threefold blindness: he taught that the world is eternal, that all people share one agent intellect (the active principle of understanding), and that there are no rewards or punishments after death. Plato and Plotinus avoided these mistakes, but because they lacked Christian faith, they could not see the whole truth. For Bonaventure, faith alone enables one to avoid error in these important matters.

Bonaventure did not confuse philosophy with theology. Philosophy is knowledge of the things of nature and the soul that is innate in human beings or acquired through their own efforts, whereas theology is knowledge of heavenly things that is based on faith and divine revelation. Bonaventure, however, rejected the practical separation of philosophy from theology. Philosophy needs the guidance of faith; far from being self-sufficient, it is but a stage in a progression toward the higher knowledge that culminates in the vision of God.

For Bonaventure, every creature to some degree bears the mark of its Creator. The soul has been made in the very image of God. Thus, the universe is like a book in which the triune God (the God of the Trinity) is revealed. His Itinerarium mentis in Deum (1259; The Soul’s Journey into God) follows Augustine’s path to God, from the external world to the interior world of the mind and then beyond the mind from the temporal to the eternal. Throughout this journey, human beings are aided by a moral and intellectual divine illumination. The mind has been created with an innate idea of God so that, as Anselm pointed out, humans cannot think that God does not exist. In a terse reformulation of the Anselmian argument for God’s existence, Bonaventure states that if God is God, he exists.

St. Albertus Magnus

The achievement of the Dominican friar St. Albertus Magnus was of vital importance for the development of medieval philosophy. A person of immense erudition and intellectual curiosity, he was one of the first to recognize the true value of the newly translated Greco-Arabic scientific and philosophical literature. Everything he considered valuable in it he included in his encyclopaedic writings. He set out to teach this literature to his contemporaries and in particular to make the philosophy of Aristotle, whom he considered to be the greatest of all philosophers, understandable to them. He also proposed to write original works in order to complete what was lacking in the Aristotelian system. In no small measure, the triumph of Aristotelianism in the 13th century can be attributed to Albertus Magnus.

Albertus Magnus’s observations and discoveries in the natural sciences advanced botany, zoology, and mineralogy. In philosophy he was less original and creative than his famous pupil Aquinas. Albertus Magnus produced a synthesis of Aristotelianism and Neoplatonism, blending together the philosophies of Aristotle, Avicenna, and Ibn Gabirol and, among Christians, Augustine and Pseudo-Dionysius.

St. Thomas Aquinas

Albertus Magnus’s Dominican confrere and pupil St. Thomas Aquinas shared his master’s great esteem for the ancient philosophers, especially Aristotle, and also for the more recent Islamic and Jewish thinkers. He welcomed truth wherever he found it and used it for the enrichment of Christian thought. For him, reason and faith cannot contradict each other, because they come from the same divine source. In his day, conservative theologians and philosophers regarded Aristotle with suspicion and leaned toward the more traditional Christian Neoplatonism. Aquinas realized that their suspicion was partly due to the fact that Aristotle’s philosophy had been distorted by the Islamic commentators, so he wrote his own commentaries to show the essential soundness of Aristotle’s system and to convince his contemporaries of its value for Christian theology.

Aquinas’s own philosophical views are best expressed in his theological works, especially his Summa theologiae (1265/66–1273) and Summa contra gentiles (1258–64; Summa Against the Gentiles). In these works he clearly distinguished between the domains and methods of philosophy and theology. The philosopher seeks the first causes of things, beginning with data furnished by the senses; the subject of the theologian’s inquiry is God as revealed in sacred scripture. In theology, appeal to authority carries the most weight; in philosophy, it carries the least.

Aquinas found Aristotelianism and, to a lesser extent, Platonism useful instruments for Christian thought and communication, but he transformed and deepened everything he borrowed from them. For example, he adopted Aristotle’s proof of the existence of a primary unmoved mover, but the primary mover at which Aquinas arrived is very different from that of Aristotle; it is in fact the God of Judaism and Christianity. He also adopted Aristotle’s teaching that the soul is the human being’s form and the body the human being’s matter, but for Aquinas this does not entail, as it did for the Aristotelians, the denial of the immortality of the soul or the ultimate value of the individual. Aquinas never compromised Christian doctrine by bringing it into line with the current Aristotelianism; rather, he modified and corrected the latter whenever it clashed with Christian belief. The harmony he established between Aristotelianism and Christianity was not forced but achieved by a new understanding of philosophical principles, especially the notion of being, which he conceived as the act of existing (esse). For him, God is pure being, or the act of existing. Creatures participate in being according to their essence; for example, human beings participate in being, or the act of existing, to the extent that their humanity, or essence, permits. The fundamental distinction between God and creatures is that creatures have a real composition of essence and existence, whereas God’s essence is his existence.

Averroists

A group of masters in the faculty of arts at Paris welcomed Aristotle’s philosophy and taught it in disregard of its possible opposition to the Christian faith. They wanted to be philosophers, not theologians, and to them this meant following the Aristotelian system. Because Averroës was the recognized commentator on Aristotle, they generally interpreted Aristotle’s thought in an Averroistic way. Hence, in their own day they were known as “Averroists”; today they are often called “Latin Averroists” because they taught in Latin. Their leader, Siger de Brabant (c. 1240–c. 1281), taught as rationally demonstrated certain Aristotelian doctrines that contradicted the faith, such as the eternity of the world and the oneness of the intellect. The Latin Averroists were accused of holding a “double truth”—i.e., of maintaining the existence of two contradictory truths, one commanded by faith, the other taught by reason. Although Siger never proposed philosophical conclusions contrary to faith, other members of this group upheld the right and duty of the philosopher to follow human reason to its natural conclusions, even when they contradicted the truths of faith.

This growing rationalism confirmed the belief of theologians of a traditionalist cast that the pagan and Islamic philosophies would destroy the Christian faith. They attacked these philosophies in treatises such as Errores philosophorum (1270; The Errors of the Philosophers) by Giles of Rome (c. 1243–1316). In 1277 the bishop of Paris condemned 219 propositions based on the new trend toward rationalism and naturalism. These included even some of Aquinas’s Aristotelian doctrines. In the same year, the archbishop of Canterbury made a similar condemnation at Oxford. These reactions to the novel trends in philosophy did not prevent the Averroists from treating philosophical questions apart from religious considerations. Theologians, for their part, were increasingly suspicious of the philosophers and less optimistic about the ultimate reconciliation of philosophy and theology.