Philosophy Pages

    Dictionary    Study Guide  Logic   F A Q s
  History Timeline Philosophers   Locke

Bonaventure and Aquinas

Reviving the West

During the thirteenth century, Christian Europe finally began to assimilate the lively intellectual traditions of the Jews and Arabs. Translations of ancient Greek texts (and the fine Arabic commentaries on them) into Latin made the full range of Aristotelean philosophy available to Western thinkers. This encouraged significant modifications of the prevalent neoplatonic emanation-theory. Robert Grosseteste, for example, followed Ibn Sina in emphasizing the causal regularity evidenced by our experience of the world, and Siger of Brabant used the commentaries of Ibn Rushd as the basis for his thoroughly Aristotelean views.

In England, Roger Bacon initiated a national tradition of empiricist thinking. Bacon proposed a systematic plan for supplementing our meager knowledge of the external world. Although he granted that consultation of the ancient authorities has some value, Bacon argued that it is even more important to employ individual experience for experimental confirmation. In coming generations, this reliance upon experimental methods would become vital for the development of modern science.

When universities developed in the great cities of Europe during this era, rival clerical orders within the church began to battle for political and intellectual control over these centers of educational life. At Paris during the thirteenth century, two of the newest orders found their most capable philosophical representatives.

The Franciscans, founded by Francis of Assisi in 1209, were initially the philosophical conservatives. As their leader in mid-century, Bonaventure defended a traditional Augustine's theology, blending only a little of Aristotle in with the more traditional neoplatonic elements. In later generations, however, members of this order were leaders in the anti-rationalistic attacks that brought an effective end to scholastic traditions.

The Dominican order, founded by Dominic in 1215, on the other hand, placed great emphasis on the use of reason and made extensive use of Aristotelean materials. Thus, their finest expositor was Aquinas, whose works became definitive of Dominican (and, eventually, of Catholic) philosophy. Later Dominicans, like Savonarola, were more likely to pursue political power than philosophical truth.


After studying in Paris with Alexander of Hales, Bonaventure taught and wrote extensively, leading his Franciscans in the measured defense of the scholastic synthesis of Platonic philosophy with Christian doctrine. Like Anselm, Bonaventure supposed that truth can emerge from rational argumentation only when the methods of philosophy are illuminated by religious faith. Thus, efforts to prove god's existence naturally begin with religious conviction itself, as an internal evidence of creaturely dependence on the deity.

Bonaventure held that the notion of an eternal material order is contradictory, so that reason itself supports the Christian doctrine of creation. Since god is the central being from which all else then emanates, every creature—including even human beings with sinful natures—may be regarded as a footprint (Lat., vestiguum) of the divine reality. Thus, in the language of Christian doctrine, we are made in god's image and likeness; or, as Plato might have put it, we participate (partly) in the Form of the Good. Even matter itself is endowed by the creator with seminal urges by means of which effective causation can proceed from within.

Despite his general commitment to neoplatonic principles and rejection of Aristotelean metaphysics, Bonaventure did accept the notion of human nature as a hylomorphic composite. Although the human soul is indeed the form of the human body, Bonaventure maintained however, it is capable, with the help of god, of continuing to exist after the death of the body. Thus, as always, he accepted the thought of Aristotle only so far as it could be made to conform to his preconceptions about Christian doctrine. As we'll see next time, one of his contemporaries at Paris used a very different approach.

Aquinas: Christian Aristoteleanism

Life and Works
. . Faith & Reason
. . Five Ways
. . Metaphysics
Internet Sources

The most profoundly influential of all the medieval philosophers was the Dominican Thomas Aquinas, whose brilliant efforts in defence of Christian theology earned him a reputation as "the angelic teacher." His willingness to employ rational argumentation generally and the metaphysical and epistemological teachings of Aristotle in particular marked a significant departure from the neoplatonic/Augustinian tradition that had dominated so much of the middle ages. Aquinas showed the church that it was possible to incorporate many of the "new" teachings of "the Philosopher" (Aristotle) without falling into the mistaken excesses of "the Commentator" (Ibn Rushd), and this became the basis for a lasting synthesis.

For Aquinas, theology is a science in which careful application of reason will yield the demonstrative certainty of theoretical knowledge. Of course it is possible to accept religious teachings from revealed sources by faith alone, and Aquinas granted that this always remains the most widely accessible route to Christian orthodoxy. But for those whose capacity to reason is well-developed, it is always better to establish the most fundamental principles on the use of reason. Even though simple faith is enough to satisfy most people, for example, Aquinas believed it possible, appropriate, and desirable to demonstrate the existence of god by rational means.

Five Ways to Prove God's Existence

Anselm's Ontological Argument is not acceptable, Aquinas argued, since we are in fact ignorant of the divine essence from which it is presumed to begin. We cannot hope to demonstrate the necessary existence of a being whose true nature we cannot even conceive by direct or positive means. Instead, Aquinas held, we must begin with the sensory experiences we do understand and reason upward from them to their origin in something eternal. In this vein, Aquinas presented his own "Five Ways" to prove the existence of god.

The first three of these ways are all variations of the Cosmological Argument. The first way is an argument from motion, derived fairly directly from Aristotle's Metaphysics:

  1. There is something moving.
  2. Everything that moves is put into motion by something else.
  3. But this series of antecedent movers cannot reach back infinitely.
  4. Therefore, there must be a first mover (which is god).
The first premise is firmly rooted in sensory experience, and the second is based on accepted notions about potentiality and actuality. In defence of the third, Aquinas noted that if the series were infinite then there would be no first, and hence no second, or third, etc. The second way has the same structure, but begins from experience of an instance of efficient causation, and the third way relies more heavily upon a distinction between contingent and necessary being.

In all of its forms, the Cosmological Argument is open to serious challenge. Notice that if the second premise is wholly and literally true, then the conclusion must be false. If, on the other hand, it is possible for something to move without being put into motion by another, then why might there not be hundreds of "first movers" instead of only one? Besides, it is by no means obvious that the Aristotelean notions of a "first mover" or "first cause" bear much resemblance to the god of Christianity. So even if the argument succeeded it might be of little use in defence of orthodox religion.

Aquinas's fourth way is a variety of Moral Argument. It begins with the factual claim that we do make judgments about the relative perfection of ordinary things. But the capacity to do so, Aquinas argued, presupposes an absolute standard of perfection to which we compare everything else. This argument relies more heavily on Platonic and Augustinian notions, and has the advantage of defending the existence of god as moral exemplar rather than as abstract intitiator of reality.

The fifth way is the Teleological Argument: the order and arrangement of the natural world (not merely its existence) bespeaks the deliberate design of an intelligent creator. Although it is an argument by analogy which can at best offer only probable reason for believing the truth of its conclusion, this proof offers a concept of god that most fully corresponds to the traditional elements of medieval Christian theology. Since its empirical basis lies in our understanding of the operation of nature, this line of reasoning tends to become more compelling the more thorough our scientific knowledge is advanced.

The Created World

Since the nature of god can be known only analogically by reference to the created world, Aquinas believed it worthwhile to devote great attention to the operation of nature. Here, of course, the basic approach is that of Aristotle, but the commentaries of Ibn Rushd provide a reliable guide as well.

Although we cannot rationally eliminate the possiblity that matter itself is co-eternal with god, Aquinas held, that undifferentiated prime matter can be nothing but pure potentiality in any case. It is only through god's bestowal of a substantial essence upon some portion of prime matter that a real material thing comes into existence. Thus, everything is, in some sense, a hylomorphic composite of matter and form for Aquinas, and god is the creator of all.

But, of course, human beings are a special case. As Aristotle had supposed, the human soul is the formal, efficient, and final cause of the human body. But in this one special instance, Aquinas held that god can add existence directly, without any admixture of prime matter, thus making possible the immortality of disembodied human souls.

Even in this life, Aquinas argued, the intellect is a higher faculty than the will in virtue of its greater degree of independence from the body. As the agent of knowledge, the human intellect comprehends the essences of things directly, making use of sensory information only as the starting-point for its fundamentally rational determinations. Although not all of Aquinas's contemporaries recognized, understood, or accepted this view of human knowledge, it provided ample room for the development of empirical investigations of the material world within the context of traditional Christian doctrine.

. . . . .
History of Philosophy
Previous Next

Creative Commons License
The Philosophy Pages by Garth Kemerling are licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
Permissions beyond the scope of this license may be available at

©1997, 2011 Garth Kemerling.
Last modified 12 November 2011.
Questions, comments, and suggestions may be sent to:
the Contact Page.