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Medieval Philosophy

Having devoted extensive attention to the development of philosophy among the ancient Greeks, we'll now cover more than a millenium of Western thought more briefly. The very name "medieval" (literally, "the in-between time") philosophy suggests the tendency of modern thinkers to skip rather directly from Aristotle to the Renaissance. What seemed to justify that attitude was the tendency of philosophers during this period to seek orthodoxy as well as truth.

Nearly all of the medieval thinkers—Jewish, Christian, and Muslim—were pre-occupied with some version of the attempt to synthesis philosophy with religion. Early on, the neoplatonism philosophy of Plotinus seemed to provide the most convenient intellectual support for religious doctrine. But later in the medieval era, thanks especially to the work of the Arabic-language thinkers, Aristotle's metaphysics gained a wider acceptance. In every case, the goal was to provide a respectable philosophical foundation for theological positions. In the process, much of that foundation was effectively absorbed into the theology itself, so that much of what we now regard as Christian doctrine has its origins in Greek philosophy more than in the Biblical tradition.

Augustine: Christian Platonism

Life and Works
. . Platonism
. . Human Nature
. . God
. . Freedom
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The first truly great medieval philosopher was Augustine of Hippo, a North African rhetorician and devotee of Manichaeanism who converted to Christianity under the influence of Ambrose and devoted his career to the exposition of a philosophical system that employed neoplatonic elements in support of Christian orthodoxy. The keynote of Augustine's method is "Credo ut intellegiam" ("I believe in order that I may understand"), the notion that human reason in general and philosophy in particular are useful only to those who already have faith.

Thus, for example, Augustine simply rejected the epistemological criticisms mounted by the Academic skeptics. Even if it were true that I am mistaken about nearly everything that I suppose to be true, he argued, one inescapable truth will remain: "Si fallor, sum" ("If I am mistaken, I exist"). [This doctrine is an interesting anticipation of Descartes's later attempt to establish knowledge on the phrase "Cogito ergo sum".] Upon this foundation, Augustine believed it possible to employ human faculties of sense and reason effectively in the pursuit of substantive knowledge of the world.

Human Life

Although Augustine was significantly influenced by the moral philosophy of Cicero, he generally argued that the Stoics were excessively optimistic in their assessment of human nature. One of Augustine's central contributions to the development of Christian theology was his heavy emphasis on the reality of human evil. Each one of us, he believed, is sinful by nature, and the account of his own life provided in the early portions of the Confessions makes it clear that he did not suppose himself to be an exception.

If, as Augustine certainly believed, the world and everything in it is the creation of a perfectly good god, then how can the human beings who constitute so prominent a part of that creation be inherently evil? Like Plato and Plotinus, but unlike the Manichaeans, Augustine now argued that evil is not anything real, but rather is merely the absence of good. Creation of human beings who have the freedom to decide how to act on their own, he maintained, is so vital a part of the divine plan for the cosmos that it outweighs the obvious consequence that we nearly always choose badly.

But if human beings begin with original sin and are therefore inherently evil, what is the point of morality? Augustine held that the classical attempts to achieve virtue by discipline, training, and reason are all boud to fail. Thus, the redemptive action of god's grace alone offers hope. Again using his own life as an example, Augustine maintained that we can do nothing but wait for god to work with us in the production of a worthwhile life. (Our happiness never enters into the picture.)

God's Existence

That there is indeed a god, Augustine proved in fine Platonic fashion: Begin with the fact that we are capable of achieving mathematical knowledge, and remember that, as Plato demonstrated, this awareness transcends the sensory realm of appearances entirely. Our knowledge of eternal mathematical truths thus establishes the immateriality and immortality of our own rational souls. (So far, the argument is straight out of Plato's Phaedo.)

Augustine further argued that the eternal existence of numbers and of the mathematical relations that obtain among them requires some additional metaphysical support. There must be some even greater being that is the eternal source of the reality of these things, and that, of course, must be god. Thus, Augustine endorses a Plotinian concept of god as the central core from which all of reality emanates.

But notice that if the truths of mathematics depend for their reality upon the creative activity of the deity, it follows that god could change them merely by willing them to be different. This is an extreme version of a belief known as voluntarism, according to which 2 + 3 = 5 remains true only so long as god wills it to be so. We can still balance our checkbooks with confidence because, of course, god invariably wills eternally. But in principle, Augustine held that even necessary truths are actually contingent upon the exercise of the divine will.

Human Freedom

This emphasis on the infinite power of god's will raises a significant question about our own capacity to will and to act freely. If, as Augustine supposed, god has infinite power and knowledge of every sort, then god can cause me to act in particular ways simply by willing that I do so, and in every case god knows in advance in what way I will act, long before I even contemplate doing so. From this, it would seem naturally to follow that I have no will of my own, cannot act of my own volition, and therefore should not be held morally responsible for what I do. Surely marionettes are not to be held accountable for the deeds they perform with so many strings attached.

Augustine's answer to this predicament lies in his analysis of time. A god who is eternal must stand wholly outside the realm of time as we know it, and since god is infinitely more real than we are, it follows that time itself does not exist at the level of the infinitely real. The passage of time, the directionality of knowledge, and all temporal relations are therefore nothing more than features of our limited minds. And it is within these limitations, Augustine supposed, that we feel free, act on our volitions, and are responsible for what we do. God's foreknowledge, grounded outside the temporal order, has no bearing on the temporal nature of our moral responsibility. Once again, a true understanding of the divine plan behind creation resolves every apparent conflict.

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Philosophical Ethics
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The End of Hellenism

European culture developed only very slowly after the collapse of the Roman Empire in 427. Theological controversies and narrow-minded defenses of traditional doctrine and practice were the sole pre-occupations of educated clergy. During these "Dark Ages," concern with the necessities of life and anti-intellectual sentiment in the church did little to encourage philosophical speculation. Although many nameless individuals worked to preserve the written tradition of what had gone before, there were few genuine high points in our philosophical history for a few hundred years.

An anonymous Christian writer of the fifth or sixth century (later designated as the pseudo-Dionysius) distinguished between two distinct approaches that human beings might take in their efforts to understand god. The via positiva is the method of reasoning analogically from the perceived nature of existing objects through successive layers of causal emanations until we arrive at some conception of the divine essence from which all flows. The via negativa, on the other hand, denies the literal truth of any comparison between natural things and god and relies instead upon mystical consciousness as the only possible source of genuine knowledge. Thus, in good neoplatonic fashion, god's unity and goodness are contrasted with the degenerate plurality and evil of the created order.


As classical scholarship began to wane, preservation of the philosophical tradition required capable translation of the central works from Greek into Latin. This labor was the great contribution of Boethius, whose translation of Aristotle's logical works provided the standard set of Latin terms for the logic of the middle ages. Moreover, Boethius's Commentary on the Isagoge of Porphyry focussed medieval attention on a metaphysical problem that arises from the simple fact that two or more things may share a common feature. The President of the United States and my youngest child, for example, have something in common, since they are both human beings.

The problem of universals asks the metaphysical question of what in reality accounts for this similarity between distinct individual substances. When we predicate of each substance the name of the species to which they both belong, what kinds of entities are truly involved? If the species itself is a third independently existing entity, then we must postulate the existence of a separate sphere of abstract beings like the Platonic forms. If, on the other hand, what is shared by both substances is nothing more than the name of the species, then our account of resemblances seems grounded on little more than linguistic whim. The difficulty of providing a satisfactory account of the predication of shared features provoked intense debate throughout the middle ages. As we'll soon see, the variety of positions adopted with respect to this metaphysical issue often served as a litmus test of academic loyalties.

Since his own life lead to imprisonment and execution, Boethius also gave careful consideration to the intellectual and ethical principles of living well. In De consolatione philosophiae (The Consolation of Philosophy), he maintained that commitment to rational discourse and decision-making is vital to the successful human life, even though it offers little prospect of avoiding the personal disasters fate holds for many of us.

John Scotus Erigena

During the ninth century, a British thinker named John Scotus Erigena applied the via negativa along with Aristotelean logic in order to develop a more carefully systematic description of the nature of reality in the neoplatonic view. Noting the crucial distinction between active (or creative) beings on the one hand and what they produce (the created) on the other, Erigena proposed that all of reality be comprehended under four simple categories:

Thus, Erigena completes the logically tidy picture with a fourth category of existence that contradicts yet must be identified with the first, emphasizing the view that only mystical consciousness can even try to grasp the nature of god. Each human being is a microcosm in whom analogues of these four fundamental elements combine to produce a dynamic whole whose existence and activity mirror those of the universe.

Few of Erigena's contemporaries appreciated the subtlety and logic of this view, however. Subordinating dialectical reasoning to the presumed dictates of revealed religion at every opportunity, many medieval writers defended and even encouraged the kind of deliberate ignorance that results from an unwillingness to question prevailing opinion. The Socratic spirit nearly disappeared.

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History of Philosophy
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Last modified 12 November 2011.
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