1) Proto-Middle Ages

In many ways, the works of two specific Church Fathers—the North African bishop, Augustine (354–430), and Roman philosopher-stateman, Boethius (480–524)—define the Latin Middle Ages since it was these two authors who established the basic scaffolding of high medieval thought, its basic conclusions, problems, and modes of argument, and its point of comparison as new ideas from the Arabic and Greek worlds entered the Latin West beginning around the twelfth century. Thus, in any history of the Middle Ages, the first period must be the proto-Middle Ages, when—under the shadow of the long-enduring institutions of classical Rome, now slowly losing their hold over western Europe and North Africa—the classical works that would eventually dominate high medieval thinking, were written.

Augustine

St. Augustine (354–430) was born in the town of Thagaste in N. Africa, at the time an important agricultural province of the Roman Empire. His mother, St. Monica, was a Christian, but his father, Patricius, was not. His parents, living on the lower fringes of the upper class of their town and hoping to make a better life for their son, made considerable sacrifices to allow him to study grammar and oratory in the metropolis of central N. Africa, Carthage. Their ambitions for their son are reflected in the name they chose for him, "Augustine," which has something of the force of "Little Emperor"—not a common name at the time (see Lancel, Augustine).

Though Augustine seems to have always been committed to Christianity in some form, as described in his famous spiritual biography, the Confessions, he would undergo a dramatic series of intellectual and spiritual conversions before eventually joining the catholic and orthodox Christian communion. First, he joined the heretical Christian sect, the Manichees, who professed a materialistic dualism in which the two gods, light and dark, were in perpetual warfare and responsibility for sin was attributed to opaque matter. The Manichees attacked the Hebrew scriptures on account of the apparent barbarity of the Hebrew patriarchs and Old Testament, creator god. Reading Cicero—who embraced a moderate form of skepticism (called "Academic" skepticism after the Academy founded by Plato in Athens)—and meeting with one of the luminaries of the Manichaean sect, Augustine became disillusioned with it, but continued to remain in it for social reasons. Finally, after reading some works of the Platonists, Augustine came to admit the existence of certain incorporeal, intellectual, or spiritual realities to which the mind could ascend within itself. 

These transformations in Augustine's thought corresponded to his journey as a teacher of oratory northward from Carthage to Rome and from Rome to Milan, where, under the influence of his mother, who had followed him, he began to listen to the preaching of the former imperial governor turned bishop, St. Ambrose of Milan (339–97), someone who was not only a political giant within the empire, but also, like himself, classically educated and capable of explaining difficult Old Testament passages in an intellectually satisfying way. After a famous conversion experience, involving the reading of Romans 13:13–14, described in his Confessions, he decided to end his relationship to his common law wife with whom he now had a adolescent son, Adeodatus, and, with his son, to enter the catholic Church. He returned to N. Africa, where he intended to live as a monk, but he was eventually compelled to become a priest and, later, bishop. As bishop, he functioned as the leading spokesperson for the bishops of N. Africa.

Augustine's intellectual endeavors as a Catholic came in roughly three overlapping periods of polemic: first, against the Manichees; second, against the Donatists; and third, against the Pelagians and the remaining pagans. The Donatists were a Christian sect in N. Africa, much like the Catholics, who had broken with the catholic communion over the question of how to treat Christians who had fallen away during the pagan imperial persecutions. Augustine's controversy with the Donatists was eventually caught up with such topics as the possibility of rebaptism, the role of priests in the administration of the sacraments, the universality of the Church, and the possibility of state coercion in Church affairs. 

Pelagianism is a loosely defined movement within Christianity associated with the British spiritual master, Pelagius (354–418), popular among the Roman, Christian aristocracy, who came to N. Africa as a refugee after the Visigothic sack of Rome in 410. Though it is difficult to identify a single common body of doctrine among the Pelagians, the debate between them and Augustine, which ended up involving thinkers from across the empire, including two bishops of Rome, centered on questions of grace, free will, original sin, the purpose of baptism, and the possibility of sinlessness. The Pelagians insisted on the possibility of sinlessness through human free will and were somewhat vague about the role of grace in human sinlessness and the reason for the possibility of infant baptism. Augustine insisted on the necessity of grace for upright action and on the necessity of infant baptism to counteract the transmission of Adam's sin by sexual reproduction.

During Augustine's time, although the empire was officially Christian, the Roman aristocracy still included many powerful pagans. When Rome was sacked by the Visigoths in 410, these pagans blamed the new religion for the city and empire's calamities. Augustine responded by writing his largest work, City of God (De civitate Dei), in which he, first, painstakingly described and attacked the popular form of Roman paganism, the superstitions of the astrologers, and the errors of the pagan philosophers. The remainder of the book was dedicated to expounding the Christian religion and salvation history. The central theme in the book is the duality of the City of God (the Kingdom of Heaven) and the City of Man—the earthly city. This book has always exercised a powerful influence over Western political thought. In the later tradition, there has been much dispute about whether or to what extent Augustine's two cities can be identified with the visible Church and the secular state, respectively.

One of the most influential aspects of Augustine's thought was his sophisticated and highly original psychology. In De magistro, which would be influential not only for medieval theologians, but also for modern philosophers, like Ludwig Wittgenstein, Augustine put forward a theory of divine illumination in which all learning comes from Christ teaching the soul from within. In De libero arbitrio, Augustine builds on his theory of divine illumination to offers an account of the ascent of the mind to God from the knowledge of immutable truths. He also offers a solution to the problem of evil (in particular, how it is that people can sin if all beings are from God, who is good, and the free will is a being), based on his metaphysical understanding of evil as a privation of being, and he provides an account of God's motive for the creation of diverse things and his permission of evil. In Against the Academics, which would be influential on Descartes, Augustine strove to give an answer to the academical skepticism of philosophers, like Cicero, that he had himself embraced in his youth. In De trinitate, Augustine defended the coherence of the orthodox Christian doctrine of the Trinity—namely, that there is only one God, but that God subsists in three persons (the Father, the Son [or the Word], and the Holy Spirit)—by saying that the persons of the Trinity do not differ absolutely, but by their mutual relations. Apart from laying the groundwork for later medieval theories of predication about God (i.e., for theories of how we can use human language to discourse about God), this book also had a foundational role in medieval psychology because of its extensive discussion of the images of the Trinity in the human mind (in human memory, intellect, and will). Especially important would be Augustine's distinction between the "inner word" (i.e., the concept in the mind) and the "outer word," perceived by the ears, which signifies the concept in the mind.

Boethius

Anicius Manlius Severinus Boethius (480–524) was a Roman philosopher and stateman living under the Ostrogothic rule of central Italy at a time when the Ostrogoths and eastern Roman Empire were vying for control of the peninsula. He was educated in Greek and Latin and attempted to preserve classical peripatetic and Platonic philosophy at a time when knowledge of Greek was waning in the West by translating Aristotle's complete works along with commentaries on these into Latin. Unfortunately, Boethius was executed by the Arian, Ostrogothic king, Theodoric, for an alleged plot against the king before he could see this massive translation project to completion. 

The translations, commentaries, and paraphrases he did complete (commentaries and translations of Porphyry's Isagoge and Aristotle's Categories and De interpretatione; paraphrases of parts of Aristotle's Analytics; and commentaries on Cicero's Topics) formed the basis of later medieval education in dialectic or logic. His contribution to medieval education in the liberal arts also included his own logical treatises and a treatise on music. 

Boethius also wrote five short theological tractates and, while in prison awaiting execution, his magnum opus, the Consolation of Philosophy, a dialogue with a personified Philosophy, who instructs him in the midst of his earthly misfortune about true and apparent happiness, fate and divine providence. This dialogue formed the basis for later medieval Christian discussions of the nature of happiness, the nature of divine eternity, and the relation of divine providence to future contingent events and sin. 

Hi Contra Eutychen (a treatise against the heresies of Eutyches and Nestorius) he discusses the hypostatic union—that is, composition of the person of Christ, the second person of the Trinity, out of two natures, human and divine. This treatise begins with a very influential section in which he explained the correspondence between basic terminology in Greek and Latin philosophy, relevant to discussions of the hypostatic union, for instance, the meaning of the words "nature" (natura), "substance" (substantia), "hypostasis" (hypostasis), "essence" (ousia), "person" (prosopon), and so on.

His theological treatise De trinitate—a treatise against the Arians, showing the possibility of three persons in one God—apart from providing a basic Augustinian model for later Trinitarian theology, stimulated medieval discussions of the problem of individuation (how there can be multiple individuals of the same kind; e.g., multiple individual humans, who are alike in species) and the problem of divine predication and simplicity (how we can attribute to God multiple non-synonymous predicates given that God is perfectly simple). 

His treatise De hebdomadibus (Quomodo substantiae), which aims to show how creatures can be good in their very substance without being God himself, who is substantial goodness itself, stimulated later medieval discussions of the transcendentals (i.e., the common attributes of every being, such as goodness, truth, and unity) and of divine simplicity and creaturely complexity. Especially important was his claim that every composite thing is composed of what it is (quod est) and its being (esse), but that in every simple thing (and he is clear God alone is simple), these two are the same. Jan Aertsen has argued that a unifying theme through all medieval philosophy is speculation about the transcendentals, the attributes common to all being.

In the High Middle Ages, an apparent (arguably not real) discrepancy between Boethius's assertions about created incorporeal substances (e.g., the human soul and angels) in De trinitate and Contra Eutychen contributed to debates about whether spiritual substances (angels) are pure forms or whether, on the contrary, they are composed of spiritual matter (i.e., matter without corporeal dimensions) and form. The latter position is known as universal hylomorphism. Likewise, an apparent discrepancy between De trinitate and Consolation of Philosophy, on the one hand, and Boethius's long commentary on the Isagoge, on the other, helped to catalyze perhaps the most well-known and highly sophisticated medieval dispute—that of the problem of universals. What is signified by common terms, like "man" or "red"? Do these terms signify real things that are themselves common to multiple individuals—to multiple humans or red things? If so, what are these common things or "universals"? Are the ideas in the mind of God (divine ideas), creatures, mere objects of thought, constructed by our mind's activity, real accidents in our intellect, or something else? The problem of universals is closely tied to the problem of individuation, closely tied to Boethius's De trinitate and Aristotle's Metaphysics VII (Z). This problem concerns the causal principle explaining the possibility of a multiplicity of individuals of the same specific kind. What accounts for the fact that Cicero and Cato are two distinct individuals if both are essentially the same thing, a man? Is it their place, their matter, their quantity, some mysterious individuating property, nothing at all, or some combination of these?

Although Boethius, unlike Augustine, is not a canonized saint in the Catholic Church, in 1883, the Sacred Congregation of Rites approved a customary local cult of Boethius in Pavia (Turner, "Anicius Manlius Severinus Boethius," in Catholic Encyclopedia, 1907).

2) Early Middle Ages

A Note on the "Fall" of Rome

In conventional histories, the Middle Ages began with the "fall" of the Roman Empire due to German barbarian invasions, the sorry state of Roman morals, and the pacifistic character of Christianity—all of which combined to produce a long "dark age." In particular, traditional histories highlight the year 476 as the official date of the fall of Rome. In this year, the Germanic Odoacer sacked Rome, deposing the last Western emperor, fittingly named Romulus Augustulus. This version of history is now known to be deeply misleading (see esp. Peter Brown, Rise of Western Christendom; Francis Oakley, The Medieval Experience).

• For one thing, the Roman Empire as such did not collapse during the fifth century. What collapsed—if anything—was the Roman Empire's control over western Europe (Gaul, Italy, Spain). Even this is overstating matters. The Roman Empire, for which Constantinople (in modern-day Türkiye) had long-since been the primary capitol, continued to exercise sporadic control over parts of the western European Mediterranean for hundreds of years, sometimes to the dismay of the native population. The Roman Empire itself survived until 1453, when Constantinople finally fell to the Ottoman Empire after centuries of glacial decline due to a variety of factors—the bubonic plague of the sixth century; the disastrous wars with the Persian, Arabic, and then Ottoman Empires; and the conquest of Constantinople by Franks and Venetians (1204) (Latin Byzantine Empire: 1204–1261). Though we often refer to the Roman Empire after the fall of the empire in the West as the "Byzantine Empire," this is a retrospective label. When the Ottomans overthrew the Byzantines, they understood themselves as overthrowing the "Romans."

• Secondly, the German cultures on the frontiers of the Roman Empire were agricultural in character and not terribly distinct from Roman culture. While contemporary moralists attributed their calamities to invading, uncivilized barbarians and decadent Roman morals, this version of events was more imagined than real.

• The "invasions" of the western Roman Empire (especially in Gaul and Italy) were really minor, local events, mostly occasioned by Roman generals themselves, who recruited German mercenaries during the Roman civil wars.

• Fourth, the "fall" of the Roman Empire in the West in the fifth century did not result in an immediate collapse in Roman culture there, but to a decentralization of Roman culture and governance such that the Roman Empire in the West devolved into a collection of local Roman-nesses, gradually evolving independently of each other. This significantly lessened the tax burden on the peasant and laboring classes (making it something of a golden age for them), but also contributed to a dramatic drop in the wealth of the higher ranks of society, on which the great intellectual and artistic monuments of a civilization depend. This is why we get the sense that this was the start of a sort of "dark age." The civilization was poorer, but the laborers and peasants were not.

• Finally, much of what was once thought to be a forced importation of Germanic culture on former Roman subjects—such as the militarization of the ruler class (who started to wear swords on their hips), the swearing of homage and fealty oaths, et cetera—in fact, reflected the mostly voluntary subsumption of the general Roman imperial populace or ruling class into a Roman-army culture that had been forced on the German mercenaries during the civil wars. Due to the decentralization of Roman governance, the Roman ruling class in the West, which had not previously been militaristic, came to take on the culture of the former Roman army, a culture now found among the German tribes, which offered protection and political stability in a newly fragmented world.

Early Medieval Philosophy as Such

With all these caveats in place about the "fall" of the Roman Empire, we can recognize a long and fairly heterogeneous period in medieval philosophy (called laconically the "Early Middle Ages") stretching from the fall of the Roman Empire in the West to the second half of the eleventh century, when a series of new factors—marked population growth, the rise of the Norman states, the papal and monastic reform movements, and the first crusade (1095–1099)—combined to usher in a new era in Western thought. 

Most histories of the Middle Ages pass very briefly over this long, second period, which produced the great encyclopedic and commentarial works of Isidore (560–636) and Bede (672–735) as well as the Neoplatonic speculations of John Scottus Eriugena (800–877). It was also during this period that two of the Greek-speaking authors who would have a tremendous influence on later Latin thought lived (or probably lived). First, there was the unknown Greek-speaking author of the Corpus Dionysiacum Areopagiticum ("Pseudo-Dionysius"), whose works were translated by Eriugena. Second, there was the Greek-speaking, Syrian Christian monk, John Damascene (675/6–749), whose theological encyclopedia, De fide orthodoxa, translated into Latin in the twelfth century, paralleled the efforts of Isidore on the other side of the Mediterranean.

4) Late Middle Ages

By the arrival of the Black Death in Europe in 1347, the principal schools and basic methods of medieval philosophy and theology had all been established. With the death of Ockham that same year, all the most famous of the medieval thinkers (Bede, Bernard, Abelard, Lombard, Bonaventure, Albert, Thomas, Scotus, and Ockham) had come and gone. Owing to the bubonic plague (1346–1353), the papal exile in Avignon (1309–1376) and Great Western Schism (1378–1417), the devastating Hundred Years War between France and England (1337–1453), the influx of new Greek texts from the Council of Florence (1431–1449) and the fall of Constantinople to the Ottomans (1453), and the introduction of the commercial printing press (1454), in the tumultuous span of about one century, Europe was violently thrust into a new era of its intellectual history. The dramatic population growth of Europe since the turn of the millennium was suddenly and catastrophically reversed, with the population being halved by the end of the fourteenth century. Likewise, the stable international order under the leadership of the bishop of Rome, so essential to the intellectual culture of the High Middle Ages, as well as the international prestige of the University of Paris, were dealt devastating blows by the Hundred Years War and Great Western Schism from which they would never recover. (For an excellent cultural history of the fourteenth-century, see Barbara Tuchman, A Distant Mirror: The Calamitous 14th Century [Alfred Knopf, 1978]).

The final phase of the Middle Ages (the “Late Middle Ages”) stretches vaguely outward with no clear terminus from the traumatic events of the mid-fourteenth century. Wherever and to whatever extent a combination of the old scholastic institutions and methods, which reached maturity in the thirteenth century, lived on, so too, in a way, did the Middle Ages. Yet, the center of gravity of the Late Middle Ages is roughly the period from the onset of the Black Death (1347) to the onset of the Protestant Reformation (1517). Arguably, the late Middle Ages includes such scholastic thinkers as John Wycliffe (d. 1384), Jean Gerson (1363–1429), Paul of Venice, OSA (1369–1429), John Capreolus, OP (1380–1444), Juan de Torquemada, OP (1388–1468), Gabriel Biel (1425–1495), Girolamo Savonarola, OP (1452–1498), Thomas de Vio, OP (“Cajetan”) (1469–1534), Francis de Vitoria, OP (1483–1546), Dominigo de Soto, OP (1494–1560), Domingo Báñez, OP (1528–1604), Robert Bellarmine, SJ (1542–1621), Francisco Suárez, SJ (1548–1617), and John of St. Thomas, OP (“Poinsot”) (1589–1644). 

Apart from the other aspects of the political and demographic turmoil of the century from the onset of the Black Death (1347) to the fall of Constantinople (1453), the Great Western Schism was particularly devastating to the scholastic tradition, which, centered on the University of Paris, depended on a relatively peaceful European international order, headed by the bishop of Rome. The Hundred Years War and Great Schism marked a transitional phase from a more international European confederation of weak feudal states, collectively headed in some degree by the bishop of Rome, to a more fragmented Europe, composed of strong, centralized nation states. With this political shift, European intellectual life also began to shift from the University of Paris to the Italian and Iberian Peninsulas. 

The decline in scholasticism was paralleled by the rise in two rather difficult to define, but closely associated ressourcement movements: “humanism” and the “Renaissance.” Among the historical catalysts for the Renaissance and Humanism were the efforts of individual scholars, such as Francis Petrarch (1304–1374) to find and recover previously neglected texts from classical antiquity in the libraries of Europe; a new interest in the classical and early Christian artifacts in Italy, especially Rome; a sudden influx of new Greek texts (as well as Greek tutors) into western Europe thanks to the Council of Florence (1431–1449) and the Ottoman conquest of the Byzantine Empire (1453); the commercial use of the printing press (beginning 1453), which, for the first time, allowed for standard editions of texts and the science of textual criticism; and the unprecedented wealth brought to Italy by the Medici Bank (founded 1397) and, later, the papal discovery of alum (1461), much of which was converted into patronage for scholarship and the arts.

The Renaissance

Though it used to be common to speak of the Renaissance as a specific period in time after the Middle Ages, this practice has justly gone out of favor. The Renaissance is now, correctly viewed as, first and foremost, a movement in literature and the fine arts, overlapping with both the late Middle Ages and early modernity, characterized by an attempt to recover literary and artistic works or methods from classical Greek and Roman antiquity as well as a fascination with Christian antiquity, its martyrs, catacombs, and lesser-known patristic writings. In neither secular nor sacred art and literature was the Renaissance purely antiquarian. Poets (e.g., Dante Alighieri [1265–1321], Giovanni Bocaccio [1313–1373], and Geoffrey Chaucer [d. 1400]) and artists (e.g., Fra Angelico [1395–1455], Filippo Lippi [1406–1469], Domenico Ghirlandaio [1448–1494], Filippino Lippi [1457–1504], Leonardo da Vinci [1452–1519], Michelangelo [1475–1564], and Raphael [1483–1520]), tried to outdo their classical counterparts. Dante, for instance, thinks he surpasses Virgil in poetry. In sacred art, the Renaissance was most novel in its attempt to depict and emphasize the humanity of Christ (and the saints) through the perfection of classical naturalistic techniques and application of these to sacred subjects. The spirituality of St. Francis (1181–1226), with its emphasis on the humanity of Christ, the empiricism of Aristotle, incorporated into scholastic theology in the thirteenth century, and the rediscovery of classical pagan models in Italy might have all contributed to this new trend in art.

Humanism

Late medieval humanism was characterized by an antagonism to the by-then-established Aristotelian methods of formal disputation in the universities and preference for newly discovered antique Latin, Greek, and Hebrew literature, outside the Aristotelian tradition—for instance, from the Greek patristic, Epicurean, Pythagorean, Hermetic, Platonic, or cabalistic traditions. Not all humanists, of course, embraced all newly recovered non-Aristotelian traditions. For instance, Erasmus and Thomas More did not think much of the hermetic or magical ressourcement of the likes of Ficino and Pico della Mirandola. Humanism was also closely associated with the so-called "devotio moderna" (exemplified in Thomas à Kempis's Imitation of Christ), a movement in Catholic devotion, which emphasized the internal and spiritual aspects of devotion over and against the external and emotional ones. It was critical of the excesses of contemporary academic theology and of popular lay devotions, such as pilgrimages, indulgences, and rote prayers.

While humanism as a movement was generally characterized by varying degrees of antagonism to scholasticism, some leading humanists—such as the bishop of Rochester and martyr, St. John Fisher, and the Spanish reformer, Cardinal Francisco Jiménez de Cisneros—combined scholastic learning with the new ressourcement of Greek and Hebrew literature. Eventually, as, in the sixteenth and seventeenth centuries, knowledge of Greek came to be the norm for scholars (and even knowledge of Hebrew quite common), and as the practice of speculative grammar and terminist logic started to decline, the distinction between scholastic and humanist mostly faded away.

Some representative humanists include Francis Petrarch (1304–1374), Giovanni Boccacchio (1313–1375), Lorenzo Valla (1407–1457), Nicolas of Cusa (1401–1464), Giovanni Pico della Mirandola (1463–1494), Marsilio Ficino (1433–1499), Francisco Jiménez de Cisneros (1436–1517), John Fisher (1469–1535), Thomas More (1478–1535), and Desiderius Erasmus (1466–1536). 

Ficino was a central figure in the newly founded "Platonic Academy" in Florence, which benefited from the patronage of Cosimo de’ Medici. Though Plato's works were relatively unknown in the Middle Ages, mostly known only through portions of Plato's cosmogonical work, Timaeus, and second-hand reports in other authors, especially Aristotle, Ficino translated Plato's complete dialogues. 

Lorenzo Valla, apart from his extensive work as translator and biblical commentator, was a pioneer and iconoclastic figure in the burgeoning field of textual criticism—taking on the authenticity of the Donation of Constantine and of Corpus Dionysiacum Areopagiticum (then treated as the deutero-canonical work of St. Paul's disciple from Athens, Dionysius) and challenging the apostolic origins of the Apostles' Creed. Though his works sparked controversy, he was buried in the papal cathedral, St. John Lateran. 

Valla's work had a significant impact on the thought of Erasmus, who was the first to publish in print the complete Greek text of the New Testament along with a new translation of it into Latin (1516)—although the Complutensian Polyglot Bible, New Testament, complete with Greek, Hebrew, and Latin, produced by Spanish scholars with the backing of the Spanish humanist, Cardinal Cisneros, had been prepared for publication, but not actually published by 1514. Despite some important scholarly flaws in its production, Erasmus's edition of the Greek Bible became the standard Greek text for generations. Apart from his work as a translator, Erasmus also wrote extensive Biblical commentaries, moralistic works, polemical treatises, and, with Thomas More, helped to pioneer a rebirth of the satirical genre.