Faith and Reason, Part 3: Aquinas

Frequent ESN contributor and InterVarsity Christian Fellowship / USA Graduate & Faculty Ministries Staff Mark Hansard returns with Part 3 of a series on faith and reason. As you may remember, Part 1 took a brief look at a Scriptural basis for using reason and logic, and Part 2 explored St. Augustine’s ideas about faith and reason. Today, Mark explores the views of Thomas Aquinas on the issue. 

We’re always happy to share Mark’s thoughtful writings. Interested in reading more by Mark? You can explore his thoughts on learning about godly scholarships through Hebrews, his popular posts on The Fruit of the Spirit in Academia, or all of his literary and theological reflections for ESN.

St Thomas Aquinas is clothed in the Dominican habit.

St Thomas Aquinas is clothed in the Dominican habit. Photo by Lawrence OP

Thomas Aquinas (1225-1274) was a theologian and philosopher who had a tremendous impact on Western philosophy and is still central to Catholic theology and philosophy today. Scholars who study Aquinas are divided about whether he believed that some propositions about God, for example, statements about his existence, can be adjudicated through reason alone, or whether they also require faith. A number of scholars believe that Aquinas thought reason alone could come to certain conclusions about God, while others argue that any statements about God require faith to believe. While this debate is quite complex, we will discuss it in rough outline here. What follows is mainly a summary of a thoughtful article by Roberto Di Ceglie.[1]

Scholars agree that, on the one hand, Aquinas states that reason should be kept autonomous from faith. This is because intellectual inquiry needs evidence, and evidence is adjudicated only through reason. Natural reason provides the “preambles” to faith (the presuppositions of faith), but not faith itself. In other words, “faith presupposes natural knowledge,” as Di Ceglie puts it, and this knowledge is naturally adjudicated through reason.

Reason is separate from faith because faith is moved by God’s love and grace, and reason is natural. This is based on the nature of evidence. Evidence “moves the intellect or senses to knowledge of them,” Di Ceglie summarizes. Thus, evidence is sensory based, reason based, but the object of faith (God or God’s truth) is not “evident” (or “seen”), according to Aquinas. In other words, evidence moves the will in a natural way through reason, but Faith is a movement of the will caused by God’s love and grace, moving the will to believe God’s revelation. As they are different sources of knowledge, they are separate.

But for Aquinas, they are not as separate as at first they might appear. According to John Jenkins, it is important to note that Aquinas’ project was quite different from John Locke’s. Regarding rational discourse, Locke sought to establish neutral propositions, statements understood through reason that were accessible to everyone, believer and unbeliever alike. Thus they did not include propositions of divine revelation or divine experience. But Aquinas had a different project in mind: he was simply attempting to adjudicate the rationality of the Christian faith using all he had at his disposal, including Christian statements of faith.[2] We know this because Aquinas declared that if the propositions discovered by philosophers contradict the faith, we must reject such propositions and then start over with natural reason to adjudicate where such evidence went wrong. Thus, Aquinas brings his faith-based knowledge of revelation into the epistemic question of what we know and how we know it. As well, it is possible to deduce from Aquinas that for him the deliverances of faith are more certain than the deliverances of reason, because the deliverances of faith are infallible, and the deliverances of reason are fallible. Thus, even when the evidence supports Christianity, the certainty comes from faith and not from reason.[3]

Therefore, while for Aquinas faith and reason are more closely related than they are in Locke, we can nevertheless see the beginnings of the split between faith and reason that would come to full fruition with Locke and other Enlightenment thinkers.

Aquinas’ View of Faith

What exactly was Aquinas’ view of faith? In the Summa Theologica he declared that it is “an act of the intellect assenting to the Divine Truth at the command of the will moved by the grace of God.”[4] In other words, it’s an act of the intellect and of the will, as the will moves the intellect to believe. The will is moved by God. Aquinas went on to discuss faith in three senses: “believing in a God,” (credere Deum), “believing God” (credere Deo), and “believing in God” (credere in Deum).[5]

The first sense, “believing in a God,” refers to the intellectual aspect of faith, an act of intellect that assents to God’s truth. In the second aspect, “believing God,” the person who exercises faith is God-dependent, because there is nothing to believe without Divine revelation. In other words, God must reveal what is to be believed to the believer (thus the dependence). In the third aspect, “believing in God,” Aquinas emphasizes that the object of our faith, God, is himself the end, or ultimate goal, of our faith. That is, as God is the ultimate Good, he is the goal of all mental and physical activity; thus the “proper task of the will,” the goodness of God, leads the person to “give assent to the revealed truth.”[6]

What this means is that faith is much more than mere intellectual assent to divine truth. It certainly includes this, but goes much further, as it “is an act intrinsically determined by affective elements.”[7] Determined, that is, by the love and pursuit of God in the believer. As well, God is not just the object of faith, he is its source. He is to be believed in, and he is the source of the revelation to be believed, thus there is a dependence on him as that source. For Aquinas, then, the things of faith “surpass human reason,” because they are supernatural in origin—people cannot believe unless God reveals his truth to them. Faith requires a “supernatural principle moving him inwardly, and this is God.”[8] But the things of faith are not contrary to human reason, they are merely above them.[9]

Thus, for Aquinas, the core of faith is the love of God. God loves people and gives them free will, yet he moves their will to “partake of him” by “generating the desire to love him more and more and believe what he has revealed.”[10] The love of God moves believers to know him and his works—in other words, all that exists.[11] And, very importantly, this love from God cannot be shelved when investigating evidence, since everything that exists comes from him, and all that comes from him is of interest since he is the object of our love. Reason investigates “reality in itself,” while faith investigates “all things as they are related to God.”[12]

Finally, Di Ceglie proposes a theory which brings reason and faith together in Aquinas. He says that according to Aquinas:

Believers’ love for God and the consequent certainty they feel about his revelation constitutes the orientation of their rational inquiry, which they develop as further confirmation of the revealed truths and as a means to clear away objections and criticisms. At the same time believers take the truth believed and loved as a criterion of their speculative investigation, since it is on the basis of the agreement or disagreement with such truth that they either accept or reject reason’s conclusions.[13]

Thus, we see with Aquinas that natural reason and faith constitute different ways of obtaining knowledge, with the supernatural movement of God in the process of faith being the superior way which brings certainty. But even though they are separate processes, they are not truly separate because the believer’s love for and pursuit of God includes all things that are related to him, which of course, means all that exists. Nevertheless, faith and reason are separate enough in Aquinas to open a crack between the two which would be widened in later centuries during the Enlightenment.


[1] Roberto Di Ceglie, “Faith, Reason, and Charity in Thomas Aquinas’s Thought,” International Journal for Philosophy of Religion (2016) 79: 133-146.

[2] John Jenkins, “Faith and Revelation,” in Philosophy of Religion: A Guide to the Subject, edited by B. Davies (Washington D.C.: Georgetown University Press, 2007), 223. Cited in Di Geglie, 137.

[3] Di Ceglie, 137.

[4] Aquinas, Summa Theologica, II-II, q. 2., a. 9.

[5] Di Ceglie, 138.

[6] Ibid., 139.

[7] P. Riga, “The act of faith in Augustine and Aquinas,” The Thomist (1971) 35: 168. Cited in Di Ceglie, 139.

[8] Aquinas, Summa Theologica, II-II, q. 6, a. 1.

[9] Bruno Niederbacher, S.J., “The Relation of Reason to Faith” in The Oxford Handbook to Aquinas (Oxford: Oxford University Press, 2012), 339.

[10] Di Ceglie, 140, summarizing Riga, 168.

[11] Di Ceglie, 140.

[12] Ibid., 141.

[13] Ibid., 144, emphasis in the original.

Print Friendly, PDF & Email

Mark Hansard

Mark is on staff with InterVarsity Christian Fellowship in Manhattan, Kansas, where he ministers to Faculty at Kansas State University and surrounding campuses. He has been in campus ministry 25 years, 14 of those years in faculty ministry. He has a Master's degree in philosophy and theology from Talbot School of Theology, La Mirada, CA, and is passionate about Jesus Christ and the life of the mind. Mark, his wife and three daughters make their home in Manhattan.

More Posts

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.