1.2 Aquinas’s Writings
I have mentioned some of Aquinas’s writings while sketching his biography. At this point, however, I should say something about them as a whole and something about Aquinas’s thinking in general.12
An important point to note is that Aquinas wrote voluminously and in works with different structures and purposes.
We have from him short philosophical treatises, like De Principiis Naturae and De Ente et Essentia. But Aquinas liked to write commentaries on various texts. So we derive a number of biblical commentaries from him: on Isaiah, Jeremiah, Job, Psalms, Matthew, John, and several letters of St. Paul.13
Then, there are a number of commentaries on works by Aristotle, such as the Sententia Libri De Anima (on Aristotle’s De Anima [On the Soul]), the Sententia Super Physicam (on Aristotle’s Physics), the Expositio Libri Perihermeneias (on Aristotle’s On Interpretation), the Expositio Libri Posteriorum (on Aristotle’s Posterior Analytics), the Sententia Libri Ethicorum (on the Nicomachean Ethics), and the Sententia Super Metaphysicam (on Aristotle’s Metaphysics).
Aquinas also wrote more than one commentary on Boethius and a commentary on Pseudo-Dionysius’s The Divine Names.14 He also commented on the Liber de Causis (The Book of Causes).15 And he produced a number of Disputed Questions. He wrote his De Veritate during his first teaching period in Paris, but he went on to edit a number of other Disputed Questions, including De Potentia (On the Power of God), De Anima, and De Malo (On Evil).
In addition to all of this we have what Jean-Pierre Torrell calls “theological syntheses.”16 These include Aquinas’s commentary on the Sentences of Peter Lombard, the Summa Theologiae, and (so I would say, though Torrell does not), the Compendium Theologiae (Compendium of Theology).17 Aquinas’s theological syntheses also include the Summa Contra Gentiles.
Aquinas produced more than the foregoing works, but you will get a sense of the range of his writing interests from what I have been saying.18 They are those of someone concerned to engage in both philosophy and theology.
Some have argued that Aquinas was not really a philosopher since his thinking is always theological, and this position is defensible for a number of reasons. Aquinas never formally taught philosophy and never describes himself as a philosopher. He would have understood the word “philosopher” to signify a pagan thinker, not a Christian, and certainly not someone functioning as a Master of Theology or a teacher of Dominicans. Again, almost all of Aquinas’s writings are heavily influenced by the Bible, from which he frequently quotes while also making numerous respectful allusions to classical Christian theologians such as Augustine of Hippo, St. Gregory the Great (540–604), and St. Jerome (347–420). Aquinas often refers to “the articles of faith,” which he takes to derive from biblical teaching and to amount to the content of Christian documents such as the Apostles’ Creed and the Nicene Creed.19 And it is the articles of faith that Aquinas is constantly trying to clarify and reflect on in many of his writings, including the SCG. So there can be no doubt that Aquinas was primarily a theologian. He takes himself to be chiefly concerned with Christian faith. In this connection, I should emphasize that Aquinas does not believe that Christian faith can be derived from purely philosophical reasoning or that it has to be. He consistently denies that the articles of faith can be philosophically proved to be true. Again, in his study of Boethius’s De Trinitate he roundly declares: “Someone may err by making reason precede faith when it comes to matters of faith rather than making faith precede reason, as when someone is willing to believe only what that person is able to discover by reason. It should in fact be just the other way around.”20
On the other hand, though, Aquinas writes a lot of what most contemporary philosophers would recognize as philosophy, even if they disagree with it. In his commentaries on Aristotle, he aims to elucidate and reflect on the work of a highly influential philosopher. Again, he spends a lot of time dealing with traditional philosophical questions such as “What are human beings?” “Can reason unaided by revelation demonstrate that God exists?” “Can we take language used to talk about God as making sense?” “What are the basic constituents of things in the spatiotemporal world?” and “Can we give people reasons for acting virtuously?” Aquinas evidently believes that he has true answers to some of these questions even before he proceeds to discuss them, answers to be found in the teachings of some distinguished Christian thinkers. Yet Aquinas also believes that he can go a long way to defending these answers without invoking the articles of faith as premises in his arguments. As I will show, Aquinas maintains that “there is a twofold mode of truth in what we profess about God.” Some of this “exceeds all the ability of the human reason,” but “there are some truths which the natural reason also is able to reach.”21 So, Aquinas holds that reason without revelation can arrive at truth about God, and he thinks the same when it comes to certain truths concerning what is not divine.22 In this sense, Aquinas is perfectly prepared to engage in philosophy, considered as a matter of rational evaluation and argument not presupposing the truth of any theological doctrine. And never more so than in the SCG.
This is obviously the work of a Christian theologian. But it is the work of one anxious to think philosophically about some key religious beliefs, especially ones about the existence and nature of God. Aquinas begins the SCG by quoting Proverbs 8:7, and biblical quotations are plentiful as the SCG proceeds, though their number increases in book 4. Yet three of the SCG’s four books consist of arguments that Aquinas offers for conclusions concerning God that he takes to be defensible without invoking the authority of the Bible, great as he takes this to be. So, three of the SCG’s four books amount to an extended essay in what is often called “natural theology.”
I take natural theology to be any attempt to reason about the existence and nature of God without dependence on purportedly divine revelation.23 Natural theology is a philosophical enterprise. Without employing theological premises, it seeks to show that we have good reason to believe that God exists and that something can truly be said when it comes to what God is. And much of the SCG offers natural theology on this understanding of it. So, as Norman Kretzmann nicely puts it, in books 1–3 of the SCG Aquinas presents “theology from the bottom up.”24 Book 4 finds Aquinas explicitly drawing on “the articles of faith” as he adds to the contents of SCG 1–3. Be that as it may, however, the bulk of the SCG is a sustained essay in natural theology.
I am told that the great twentieth-century theologian Karl Barth (1886–1968) was asked in 1962 to summarize what he said in his many writings. He is said to have replied: “Jesus loves me, that I know, for the Bible tells me so.” This story might be apocryphal, though it fits in with the drift of Barth’s theology. The point I want to stress now, however, is that, though Aquinas is in agreement with Barth when it comes to the importance of revelation, he thinks, as Barth did not, that philosophy can be quite a useful aid to theologians.25 This fact is very evident from the text of the SCG.