Athens and Jerusalem: Thomas Aquinas and the Medieval Synthesis of Reason and Faith


The beautiful St. Giles’ Cathedral in Edinburgh, Scotland


… Sacred doctrine is food and drink since it feeds and gives drink to the soul.  For the other sciences only illumine the intellect, but this illumines the soul.”

(Aquinas, Commentary on Hebrews 5:12)

Philosopher Peter Kreeft notes that “the medievals had a passion for order, because they believed that God had a passion for order when He designed the universe.”[1] Medieval scholars were preoccupied with discovering this order and then synthesizing it with the truths of Scripture. Because of the common grace spoken of in texts such as Romans 1 and Acts 17, all truth was God’s truth to them, even that which comes from pagan philosophers and poets. The medieval theologian Thomas Aquinas epitomized this “inclusive habit of mind” that sought to bring back into Christendom all that is good, true, and beautiful.[2]  In particular, Aquinas excelled at harmonizing human reason and divine faith, displaying a keen intuition as to where they stand apart and where they overlap. Kreeft notes that he “combined faith and reason, without confusing them” by establishing that there “are some truths that are known by faith alone, like the Trinity, and some that are known by reason alone, like natural science, and some that can be known by both faith and reason, like the existence of God and the freedom of the will and the immortality of the soul.”[3] Not unlike today, the challenge was defining the boundary line between Divine Scripture and human philosophy, a challenge made all the more difficult by the inevitable fallibility of the ones surveying their borders. In his book A Shorter Summa, Peter Kreeft writes that in a humble style that comes directly to the point, with logic that is refreshingly clear and grounded in common experience, Aquinas “fulfilled more than anyone else the essential medieval program of a marriage of faith and reason, revelation and philosophy, the Biblical and the classical inheritances.”[4] As mentioned, one such synthesis is represented in Aquinas’s resolution to the apparent paradox between the existence of human free-will and the divine sovereignty of the Unmoved Mover. The way in which he was able to resolve the riddle without compromising either shows us that Aquinas’s spiritual sight was truly stereoscopic: he was able to see “two different pictures at once” without sacrificing one for the other.[5]  As a result, Thomas Aquinas was able to see more while remaining within orthodoxy’s borders. Through him, our sight is likewise broadened in that he shows us a way forward in resolving our own conflicts between faith and reason.

Fueled by the rediscovery of the works of Aristotle, the marriage between the faith and reason was as threatened then as it is today as debate raged within the medieval church between “fearful, heresy-hunting … traditionalists, and the fashionable compromising of modernists.”[6] There is nothing new under the sun. In his biography on Aquinas, G.K. Chesterton contends that one could view the rediscovery of Aristotle as something of a grace, for, in its humanness, the medieval church had developed a disordered love for the philosophy of Plato. The heavenly chariot of orthodoxy was reeling from the strain and in danger of being toppled. He writes that “the Greek element in Christian theology tended more and more to be a sort of dried up Platonism; a thing of diagrams and abstractions; to the last indeed noble abstractions, but not sufficiently touched by that great thing that is by definition almost the opposite of abstraction: Incarnation.”[7] Christianity was losing sight of the fact that Jesus bridged the gap between the abstractions of the Divine Essence, forever beyond human comprehension, and the Creator God whose right hand held men fast in the darkness.[8] Its most radical of all claims – that God had become man and in doing so had declared Creation worth saving – was increasingly threatened. Aquinas was made for such a moment, it seems, for he “thought it right to correct Plato by an appeal to Aristotle; Aristotle who took things as he found them, just as Aquinas accepted things as God created them.”[9] Part of the correction involved restoring human reason to its rightly ordered place within Creation.

Aquinas’s Summa Theologiae was one such attempt at restoration. Formulated as a debate with the best objections to his arguments, Kreeft notes that Aquinas’s style of refutation in the Summa reveals an important lesson that moderns can learn from the scholastics. He writes that “a ‘scholastic disputation’ was not a personal contest in cleverness,” rather it was more like a “shared journey” towards finding truth.[10] Here again, we see a greater generosity with secular ideas and a refreshing lack of the self-conscious defensiveness that plagues our modern disputes. For medieval scholastics such as Aquinas, objections were not a threat to be taken down, but “live options to be considered and learned from.”[11] Kreeft notes that Aquinas “almost always finds some important truth hidden in each objection, which he carefully distinguishes from its error.”[12] He had great respect for the Imago Dei, and indeed, this is seen in how he used Aristotle’s philosophy to reestablish the dignity of the created order and effect a return to common sense, things that had been lost in the church’s overemphasis on asceticism and Platonism. In respecting mankind’s ability to reason, Aquinas was able to “recover what was, in essence, the body of Christ itself” and the incarnational pulse of Christianity.[13] Chesterton writes that though Aquinas was “taking the lower road when he walked in the steps of Aristotle … So was God, when He worked in the workshop of Joseph.”[14]  A contemporary and friend of Aquinas, St. Bonaventura, “complained that Aquinas’s use of Aristotle diluted the wine of the Gospel by the water of pagan philosophy. Aquinas replied, ‘No, I am transforming water into wine.’”[15]

Aquinas created a synthesis of faith and reason without confusing the two because, as Chesterton contends, he understood “what may be called subordinate sovereignties or autonomies.”[16] Here again is the assumption of an inherent hierarchy in the created order that undergirded and enlivened the entire medieval synthesis: “A place for everything and everything in the right place,” including human reason.[17] It was never a more certain (and easier) ‘either/or’ when it came to reason and faith for Aquinas, but a ‘both/and’ predicated on this ordering principle.

Aquinas’s belief in the existence of these “subordinate sovereignties and autonomies” can be seen in his resolution to the “thorny problem of reconciling human free will with divine causality.”[18] His response to the question “Whether Man Has Free-Will” begins with the obvious. “I answer that,” he writes, “Man has free-will: otherwise counsels, exhortations, commands, prohibitions, rewards, and punishments would be in vain.”[19] Indeed, and one might observe that the New Testament itself assumes this in that it counsels, exhorts, commands, prohibits, and so on, ostensibly appealing to the will of the Christian. Rather than stop there, Aquinas then uses Aristotle’s concept of teleology to describe the activity of intellect and will within the created order. In his book Aquinas, Thomist philosopher Ed Feser writes that for St. Thomas the will was simply “a power to be drawn towards (or away from) that which is apprehended by the intellect …to be good or bad, respectively.”[20] The amount of will a creature has is dependent upon its intelligence. Feser writes that Aquinas’s “answer is that though God [as the Unmoved Mover] does move the will, ‘since he moves every kind of thing according to the nature of the moveable thing … he also moves the will according to its condition, as indeterminately disposed to many things, not in a necessary way.’”[21] Aquinas writes,

God, therefore, is the first cause, Who moves causes both natural and voluntary. And just as by moving natural causes He does not prevent their acts being natural, so by moving voluntary causes He does not deprive their actions of being voluntary: but rather is He the cause of this very thing in them; for He operates in each thing according to its own nature.[22]

In other words, Kreeft writes, “If God’s being the first cause of the nature of dogs makes dogs doggy and not un-doggy, then God’s being the first cause of human freedom makes freedom free, not un-free.”[23] In this we see that, through a synthesis of faith and reason, Aquinas was able to find in “the Aristotelean doctrine of final causes” or “the inclination or tendency towards an end [that] pervades the natural order” the means by which he could retain human moral responsibility and the sovereignty of God without compromising either.[24] The consequences of this synthesis are far-reaching.

Again, as Chesterton notes, we see Aquinas “defending the independence of dependent things,” and that a faculty like human free will “could have its own rights in its own region.” [25] This is only possible from within the confines of the ordered hierarchy that the medievals took as foundational. In the end, “a place for everything and everything in the right place” turns out to be one of those “limitations that do in fact preserve and perpetuate an enlargement.”[26],[27] When moral responsibility and God’s sovereignty are ordered correctly, both are retained and enlarged. Compare this to our modern predicament where human free will is either crushed into a deterministic oblivion or is viewed as the sole ground of meaning. Either way, what can be known of God’s nature and mankind’s moral responsibility are distorted to our detriment. Instead, Aquinas was able to rescue our intuitions without diminishing God’s glory and, in the end, he revealed that there is another level of grandeur in the cathedral of our Creed.

The way in which Aquinas resolves the problem of human free will is characteristic of his approach with a myriad of other theological questions such as the problem of evil, God’s omnipresence, biblical hermeneutics, and more.  In the end, the very style of his Summa, with its painstakingly stated objections that avoid oversimplifications, its clarity of style, and its generous responses, reveals a refreshing respect for truth, regardless of its source. The key for Aquinas was that though God’s essence could never be completely known by man, He could be known through the works of His hands – the book of revelation and the book of nature. When exploring the relationship between faith and reason, philosophy and divine revelation, Aquinas gives us the following advice, both eminently reasonable and practical, that affirms Reason while putting it in a subordinate position with respect to Faith:

It was necessary for man’s salvation that there should be a knowledge revealed by God besides philosophical science built up by human reason. Firstly, indeed, because man is directed to God, as to an end that surpasses the grasp of his reason: ‘The eye hath not seen, O God, besides Thee, what things Thou hast prepared for them that wait for Thee’ (Isaiah 64:4). But the end must first be known by men who are to direct their thoughts and actions to the end. Hence it was necessary for the salvation of man that certain truths which exceed human reason should be made known to him by divine revelation. Even as regards those truths about God which human reason could have discovered, it was necessary that man should be taught by a divine revelation; because the truth about God such as reason could discover, would only be known by a few, and that after a long time, and with the admixture of many errors. Whereas man’s whole salvation, which is in God, depends upon the knowledge of this truth. Therefore, in order that the salvation of men might be brought about more fitly and more surely, it was necessary that they should be taught divine truths by divine revelation. It was therefore necessary that besides philosophical science built up by reason, there should be a sacred science learned through revelation.[28]

Peter Kreeft notes that “if there’s a common theme to most modern philosophies it’s the crisis of reason, the questioning of reason itself.”[29] Common sense is no longer common and not only do modern philosophies (and theology) suffer, so does the culture that is downstream from them. Reason needs to be returned to its rightful place within the created order. Thomas Aquinas can show us the way.


Peter Kreeft, The Modern Scholar: The Philosophy of Thomas Aquinas – Lectures on Audible

Peter Kreeft, A Shorter Summa

Ed Feser, Aquinas: Beginner’s Guide


St. Giles’ Cathedral, Edinburgh, Scotland

[1] Peter Kreeft, A Shorter Summa (San Francisco: Ignatius Press, 1993), 17.

[2] Peter Kreeft, The Modern Scholar: The Philosophy of Thomas Aquinas (New York: Recorded Books, 2009), pdf.

[3] Peter Kreeft, The Modern Scholar: The Philosophy of Thomas Aquinas, pdf.

[4] Peter Kreeft, A Shorter Summa, 15.

[5] G.K. Chesterton, Orthodoxy (Peabody, MA:  Hendrickson Publishers, 2006), 23.

[6] Peter Kreeft, A Shorter Summa, 15.

[7] G.K. Chesterton, St. Thomas Aquinas, 47.

[8] Psalm 139, NET.

[9] G.K. Chesterton, 48.

[10] Peter Kreeft, A Shorter Summa, 16

[11] Ibid., 16.

[12] Ibid.

[13] G.K. Chesterton, 17.

[14] Ibid.

[15] Ibid.

[16] Ibid.

[17] C.S. Lewis, The Discarded Image (Cambridge: Cambridge University Press, 2013), 10.

[18] Peter Kreeft, 113

[19] Ibid., 111.

[20] Edward Feser, Aquinas: Beginner’s Guide (London: OneWorld, 2009), 149.

[21] Ibid.

[22] Peter Kreeft, 113.

[23] Ibid.

[24] Ed. Feser, 149

[25] G.K. Chesterton, 15.

[26] C.S. Lewis, 15.

[27] G. K. Chesterton, The Everlasting Man (Tacoma, WA: Angelico Press, 2013), 79.

[28] Peter Kreeft, 40.

[29] Peter Kreeft, The Modern Scholar: The Philosophy of Thomas Aquinas, pdf.

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