Christian Philosophy?
Since this Thomistic Philosophy website seeks to present “the philosophical methods and principles used or inspired by Aquinas in his explanation of the Catholic faith” it would be well to consider whether and how there might be such a thing as philosophy discoverable within the work of a Catholic theologian. More generally, one must wonder whether a Christian philosophy is even possible, or does the fact that the thought is Christian, and thus dependent on Christian revelation, vitiate its philosophical character as a purely rational enterprise. This charge is typically leveled against medieval thinkers, but especially Thomas Aquinas and those in the Thomistic tradition. It is a serious charge – one that should be handled soberly and fairly by anyone claiming that his or her philosophy is truly rational knowledge and also truly Christian. What follows is a brief exploration of the problem as it is dealt with by prominent historians of theology and philosophy, and Thomists of the 20th and 21st centuries.
Faith and Philosophy
There are in fact two difficulties connected with identifying the philosophy of a believing Christian such as Thomas Aquinas. On the one hand, the Christian may wonder whether the use of philosophy somehow undercuts the authenticity of faith or makes faith superfluous. For if philosophy can prove that God exists, for instance, one need not, indeed it seems, that one cannot, believe (with religious faith) that He exists, since according to the classic definition of Christian faith in Hebrews 11:1, “faith is the substance (or realization (Greek: hypostasis)) of things to be hoped for, the evidence (or proof (Greek: elenchos)) of things not seen.” On the other hand, for the non-Christian, the worry is that the Christian does not admit philosophical conclusions that conflict with his or her faith, but preselects (based on their religious faith) a philosophy and principles that result in “conclusions” compatible with what he or she already believes, such as the existence of God and the immortality of the human soul. Indeed, the theological context of Aquinas’s use of philosophy, it must be acknowledged, is essential to understanding it and his use of it.
Any appropriate formulation [of the question how Aquinas’s philosophy is related his theology] must begin by recognizing that whatever philosophy there is in Aquinas can be approached only through his theology if it is to be approached as he intended it. Indeed, it is very difficult to separate out the philosophical passages in his works. His writings are overwhelmingly on the topics and in the genres of the medieval faculties of theology He wrote almost always in what is self-evidently the voice of a theologian.
Mark Jordan, “Theology and Philosophy,” in The Cambridge Companion to Aquinas, ed. Norman Kretzmann and Eleonore Stump (Cambridge: Cambridge University Press, 1993), p.232.
Thus, the worry is that whatever philosophical arguments a thinker such as Thomas Aquinas produces, precisely because he was a professional theologian and, for the most part, they occur in theological works, they are tainted by the Christian presuppositions and assumptions he is committed to based on his faith, undermining their rational reliability. By producing or adducing only such philosophical arguments as conform to one’s religious beliefs and only admitting “the correct answers,” the Christian runs the risk of producing bad arguments.
Knowing the correct answers in advance is, of course, not a substitute for knowing them through a logical argument based on experience. Unfortunately, having the answers can lead to intellectual laziness. Catholic thinkers must fight the temptation to be satisfied with shoddy arguments when the conclusions of these arguments happen to coincide with what is known with certitude through faith. Indeed, Christian philosophers should rather be doubly careful about their reasoning, for if they offer feeble philosophical arguments in defense of something they know to be true through faith, when a keener thinker comes along and demolishes these arguments, it tends to discredit the truth of the faith.
Marie I. George, “Trust Me. Why Should I? Aquinas on Faith and Reason,” in The Ever-Illuminating Wisdom of St. Thomas Aquinas: Papers Presented at a Conference Sponsored by the Wethersfield Institute (Ignatius Press 1999), p. 48. See also Msgr. William T. Magee, “The Situation: Seminary Education and its Critics,” in George McLean, ed., Christian Philosophy in the College and Seminary, (CUA Press 1966), pp. 86-92.
Such shoddy arguments put forward by Christian philosophers is bad both for philosophy and for the Christian faith out of which it arises and which it is meant to support or defend. But, one may wonder, need the arguments of a Christian philosopher be deficient in this regard?
Nature and Grace
Throughout his career, Thomas Aquinas was concerned with these questions, though, to be fair, he was more concerned with justifying how to incorporate secular, pagan philosophy (mostly that of Aristotle) into Christian theology, which he consistently refers to as Sacred Doctrine (Sacra Doctrina, in Latin). Yet, his concern was also with defending genuine philosophy based on, as he says, the light of natural reason, not some pseudo-reasoning which is really religious belief in rational disguise. His earliest treatment of the subject occurs in his Commentary on Boethius’s On the Trinity, which he wrote around the time he was completing the requirements to become a Master of Theology in finalizing his Commentary on the Sentence of Peter Lombard (which we will also consider below). It seems likely he wrote these early works in 1256 while he was sidelined by the disputes at the University of Paris which were ultimately resolved in Aquinas and Bonaventure’s favor by the Pope Alexander IV and King Louis IX (see Saint Thomas Aquinas biography). (Armand Maurer, Faith, Reason, and Theology (Pontifical Institute of Medieval Studies, Toronto 1987) p. vii.) Aquinas presents several elements of his program of integrating the two disciplines that respects the distinction and autonomy of each, though obviously favoring theology and his Christian faith. Perhaps, most importantly, is his insistence that grace does not destroy nature, but presupposes and builds upon (restores, perfects, and elevates) nature.
Indeed, grace is not meant to do away with human nature, but to raise and perfect it. Grace renders nature more perfect. It does so in agreement with nature’s basic characteristics.
Leo J. Elders, SVD, “Faith and Reason: The Synthesis of St. Thomas Aquinas,” Nova et Vetera, English Edition, Vol. 8, No. 3 (2010), p. 530.
In this, Aquinas’s position is opposed to the view that human nature and reason are inherently evil or irredeemably corrupt, and fundamentally opposed to grace and faith. It is useful, then, to consider the his whole answer in Question 2, Article 3 of his commentary on Boethius’s work:
I answer that it must be said that gifts of grace are added to those of nature in such a way that they do not destroy them, but rather perfect them; thus, even the light of faith, which is infused in us by grace, does not destroy the natural light of reason, given to us from God. And even though the natural light of the human mind is insufficient for the discovery of those truths revealed through faith, nevertheless it is impossible that those truths divinely handed on to us by faith should be contrary to what we are endowed with by nature. One of these would have to be false, but since we have both from God, God would be the author of our error, which is impossible. Rather, since in imperfect things there is found some likeness to the perfect, in those things known by natural reason there are certain likenesses to what is taught by faith.
Now, just as Sacred Doctrine is founded upon the light of faith, so philosophy depends upon the light of natural reason. Thus, it is impossible that things belonging to philosophy be contrary to things belonging to faith; even though they fall short of them. Nevertheless, they contain some likenesses to the latter, and a certain preparation (preambula) for them, just as nature is a preparation (preambula) for grace.
If, however, anything is found in the teachings of the philosophers contrary to faith, this does not belong to philosophy, but rather to an abuse of philosophy arising from a defect of reason. And so it is possible from the principles of philosophy to refute an error of this sort, either by showing it is altogether impossible, or is not necessary. For just as those things which belong to faith cannot be demonstratively proved, so certain things contrary to them cannot be shown demonstratively to be false. But it can be shown they are not necessary.
Thus, in Sacred Doctrine we are able to make a threefold use of philosophy:
- First, to demonstrate what are preambles of faith, which it is necessary for faith to know, such as the truths about God that can be proved by natural reason: that God exists, that God is one, and other such truths about God or creatures proved in philosophy which faith presupposes.
- Second, to better understand what belongs to the faith through certain likenesses, as Augustine in his book, On the Trinity, uses many comparisons taken from the teachings of philosophers to elucidate the Trinity.
- Third, to resist those who speak against the faith, either by showing that their statements are false, or by showing that they are not necessarily true.
Nevertheless, those using philosophy in Sacred Doctrine can err in two ways:
- In one way, by using teachings contrary to faith, which do not belong to philosophy, but are the corruption and abuse of it, as Origen did.
- In another way, by including what belongs to faith within the bounds of philosophy, as if one should be unwilling to believe anything except what could be established by philosophy. On the contrary, philosophy should be brought within the bounds of faith, according to the saying of the Apostle, “bringing into captivity every understanding unto the obedience of Christ” (2 Cor 10:5).
To this point, Aquinas adds in his Reply to Objection 5, “Wherefore those who use philosophical doctrines in Sacred Doctrine in service to the faith, do not mix water with wine, but change water into wine.” We will examine the import of this Biblical analogy in the context of Aquinas’s mature thought below.
For now, it is enough to note that Aquinas, even in this very early work, sees the value and autonomy of philosophy originating, like grace and faith, in God, Who is, as Aquinas will later teach, Truth Itself. (ST I, q. 16, a. 5) Philosophy, then, is useful to theology if, and only if, it is true, and just to the extent it is true.. If a proposition is false, Aquinas writes, it is not philosophy, nor the product of natural reason, but an abuse of these.
Thomas vindicates the autonomy of philosophy, while in theology he uses without any hesitation many philosophical concepts, definitions, principles, and analyses, which he recognizes as true. His certitude concerning their truth is based on their intrinsic evidence and on their astonishing harmony with the doctrine of faith.
Elders, art. cit., p. 540.
A teaching’s truth is its guarantee that it originates in God, and so he is confident that it must be compatible with faith. And since divine grace guarantees that faith and revelation are true, what conflicts with faith cannot be, nor can it truly (pun intended) be philosophy.
By the same token, Aquinas argues, it belongs to philosophy as an exercise in natural reasoning to discover the error in arguments opposed to the faith and correct them, or at least show that the conclusion is not necessary. During his second Paris tenure which began in 1269, Aquinas engaged in these sorts of philosophical exercises to show that Latin Averroist positions mentioned before – e.g., all people having a common intellect – are false and not what Aristotle taught. Similarly, Aquinas argues philosophically that the eternity of the world, which Aristotle did teach, is not a necessary conclusion. He does not try to prove, however, that the universe had a beginning in time, as he believed that that could only be known because God reveals it in Scripture. Both erroneous positions relate to matters of faith in challenging the possibility of life after death and the truth and reliability of Scripture. They also challenge the reputation of Aristotle as a reliable teacher of true philosophy, which Aquinas was likewise eager to defend.
Late in his career, Thomas again returns to the distinction and relation between philosophy and theology in the very first question of the Summa Theologiae, where he explains the nature and method of Sacred Doctrine (Sacra Doctrina), his term for Christian theology (which, as we will see below, seems to include, but extends beyond Sacred Scripture, i.e., the official, public revelation contained in the Bible). His very first article of this question asks “Whether it is necessary to have any doctrine besides philosophy?” Thomas is more concerned with the first of the two concerns about philosophy in the works of a Christian theologian, i.e., whether the use of philosophy within theology takes anything away from theology’s reliance on faith in Scripture, but his treatment of the relationship between the two sciences gives cogent reasons for how and why Christian philosophy, Thomistic philosophy in particular, is legitimately rational and natural (and not inherently religious or supernatural) when considered apart from its admittedly Christian context.
In this first article of the first question of the Summa, Thomas Aquinas endeavors to delineate the difference between philosophy and theology. The article asks whether there is a need for any knowledge beyond philosophy since it investigates everything that exists, even God. Aquinas writes that there is such a need, first because union with God is the goal of human life, and this goal is beyond what reason can grasp (or unaided human effort can achieve). But in order to do what is necessary to attain the goal, people must at least know what it is. “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.” So, theology teaches truths about God and how to achieve salvation which no one could discover by natural reason, unless God revealed them, and as Aquinas will state later (in Article 8, Reply to Objection 2) people accept this revelation in faith. Secondly, while reason can know some things about God through philosophy, this only happens with difficulty. “[T]he 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.” So, God revealed even naturally discoverable truths to allow people to receive salvation “more fittingly and more surely” (et convenientius et certius). He sets the stage, as it were, for his own explanation of how theology contains such naturally knowable truths about God without taking away from faith, and how such philosophical knowledge does not depend on the revelation and faith that characterizes theology. But Aquinas, in his Reply to Objection 2 makes clear, that each intellectual pursuit operates by different lights, i.e., principles and cognitive focus: “philosophical disciplines teach about those things knowable by the light of natural reason that another science (i.e., theology) teaches according as they are known by the light of divine revelation.”
What Scripture Teaches about Philosophy
Some historians argue that Thomas Aquinas’s inclusion of philosophy in his works, especially the Summa Theologiae, is wholly theological. Jaroslav Pelikan, for instance, in the third volume of his series, The Christian Tradition: a history of the development of doctrine contends that Aquinas the theologian employs arguments from natural reason because Christian Scripture indicates that unaided human reason can attain knowledge of God. In particular, because Scripture reveals God’s self-definition “I am who am” (Exodus 3:14) and that “the invisible things of God are clearly seen, being understood through the things that have been made” (Romans I: 20), Aquinas, according to Pelikan, includes philosophical demonstrations as part of his theological works.
That self-definition from Exodus 3:14, in combination with the standard proof text for natural theology from Romans I: 20, provided Thomas Aquinas with the necessary biblical support for undertaking to prove the existence of God by reason. Hence it was by the authority of revelation that the theologian proceeded to argue even apart from revelation that God could be known from his creation.
Jaroslav Pelikan, The Growth of Medieval Theology (600-1300) (Chicago: University of Chicago Press, 1978), 289.
Thus, since Scripture says that reason can know the existence of God, the theologian, Aquinas in this case, tries to show the correctness of scripture by actually producing at least one (or five in the Summa Theologiae I, q. 2, a. 3) proof of God’s existence.
The equation of the God of Abraham, Isaac and Jacob with the first principle of being permitted the theologian, charged as he was with the task of expounding the doctrinal tradition, to engage also in the philosophical enterprise of measuring the capacity of reason to establish the truth of the divine being; and in this sense he was obliged to state a natural theology.
Ibid.
According to Pelikan, the reason Aquinas includes philosophy in a work of theology is that Scripture indicates that reason is sufficient to reach God. Moreover, this indication by Scripture is truly theological since it implies something about the state of man after the Fall of Adam and Eve in the Original Sin. The theologian thus engages in philosophical demonstrations of God’s existence because Scripture says it is within the power of unaided reason.
Evidently Pelikan takes the On the contrary (sed contras) sections of aa. 2-3 of q. 2 as Aquinas stating his magisterial and explicit reason for the inclusion of philosophy in the Summa. Thus, in determining that the existence of God can be demonstrated, the sed contra of q. 2, a. 2 cites Romans I, 20, and as a prelude to the Five Ways in a. 3, that sed contra cites Exodus. However, not many of those familiar with the Summa Theologiae or the medieval quaestio disputata format would give as much weight to sed contras as to arguments for the author’s own position. They merely give an indication that the objections are off target.
Since this part (sed contra) of the development almost always prefigures Aquinas’s reasoned reply, it is often meager in itself, simply reminding the reader that there are good reasons for taking the other side seriously.
Jan Aertsen, in The Cambridge Companion to Aquinas, pp. 18‑19.
More importantly, Pelikan’s argument fundamentally undermines the autonomy of philosophy even while being incorporated into a summary of theology. For if the theologian accepts on faith and as his starting point the claim that the existence of God can be proved rationally, then he is giving to a supposedly philosophical proof a conclusion known through faith. Furthermore, he is making the assertion that the proof will successfully pass from premises to its conclusion and makes this assertion on the basis of faith. However, Aquinas in a later article of Question 1 writes that it is not the job of the theologian to give to philosophy either its premises or its conclusion. “Therefore, it does not pertain to [theology] to prove the principles of other sciences, but only to judge them” (ST I.1.6 reply 2). Rather, as we will see below, Aquinas tells us, theology uses philosophy as a handmaid (ST I.1.5 reply 2) formally incorporating it into itself, yet leaving the independence of its principles and natural light intact. It seems that in order to maintain truly natural knowledge of God within a theology that takes its principles from revelation, there must be another way it is integrated than how Pelikan suggests.
Moment of Discovery and Moment of Truth
John Wippel claims that philosophy in a Christian thinker’s theology may maintain its freedom from theological absorption and so be useful to the non-Christian by limiting the influence revelation exerts on a Christian’s philosophy only to its beginning. Wippel distinguishes two moments in a Christian’s philosophical journey, the “moment of discovery” and “the moment of proof.” The moment of discovery occurs when the philosopher is presented, or presents to him- or herself some aspect of reality to investigate. The moment of proof comes when one has reached a demonstrative conclusion as the result of syllogistic reasoning. The moment of proof is strictly philosophic both in its form and content, for what it knows is learned or demonstrated by unaided, natural reason using purely rational principles. The moment of discovery, however, as merely considering which truths one believes might be susceptible of rational investigation, is philosophic in content, albeit not systematized or tested; i.e., it is not philosophic in form.
As Wippel uses the distinction, the influence of faith upon philosophy is intrinsic in its moment of discovery and extrinsic in its moment of proof. Christian philosophy, that of Aquinas or of other medieval theologians more generally, then, could have been influenced by faith and revelation in its moment of discovery. Wippel readily grants “that a typical Christian medieval thinker was influenced in his original acceptance of a given point by his prior religious belief in the same, or in what might be called the ‘moment of discovery.’” (John Wippel, “Thomas Aquinas and the Problem of Christian Philosophy,” in Metaphysical Themes in Thomas Aquinas (Catholic University Press 1984), p. 23) In contrast to Pelikan who says the Christian philosopher accepts the revelation of Scripture that God’s existence can be proved (e.g., Romans I, 20), Wippel views the Christian philosopher as a philosopher who considers whether what he believes as a Christian as supernaturally revealed, can also be known rationally.
In its moment of proof, however, the philosopher proceeds from principles known to reason alone. Such a medieval thinker could never, of course, admit a revealed premise into his attempted philosophic demonstration of a given conclusion without thereby passing from philosophy to theology. One should not, therefore, refer to philosophy as Christian in its “moment of proof”
Ibid., pp. 23-4.
Wippel thus does not consider philosophy in the moment of proof as susceptible to the appellation Christian. The relationship of faith to philosophy in this initial moment of the philosophical enterprise is entirely extrinsic.
This view acknowledges some point of content between the Christian faith of the one philosophizing, and it attempts to shield the ensuing exercise of natural reason from it. In so doing, it also diminishes the content of the Christian philosophers store of religious tenets believed in, since Aquinas is explicit that one and the same person cannot both believe with religious faith the same truth that one knows as rationally demonstrated. (ST II-II, q. 1, a. 5) Of course Aquinas does allow that what person one may know by demonstration, another may believe with faith. (Reply to objection 3)
Wippel, of course, acknowledges Aquinas’s position on this, (pp. 3-4) yet seems to consider that what is impossible is only that the same truth being both known through reason and believed through faith in the same temporal moment, i.e., “that one cannot believe and know the same thing at the same time.” (Ibid., fn. 8, emphasis mine) One may, it seems, first believe, e.g., that God exists as part of His revelation, and later, come to know the same truth on the basis of rational argument. Indeed, this seems to be the procedure Aquinas envisions for those few Christians who are able to successfully prove God’s existence.
Thus, the moment of discovery does seem to amount to willing suspension of religious belief, but it occurs as an interruption in the subjective life of believing for the Christian philosopher. Nevertheless, when the proof is complete, and what was once believed has become a conclusion of philosophy, the Christian no longer believes with religious faith that tenet, but sees it as true, and knows it scientifically. It should be noted that this contracting of belief by proof only applies to preambles to faith, which Aquinas mentioned in his Commentary on Boethius’s On the Trinity that few, if any, Christians would actually come to know, and only late in life and with great difficulty or uncertainty. (See ST II-II, q. 2, a. 4; see ST, q. 1, a. 1 below). As such, are not central or essential tenets of the Christian faith, but what must be accepted as true in order to accept what is essential. “Those things that can be known through natural reason, granted that not all will arrive at such knowledge, pertain to the faith only in a qualified way.” (George, art. cit., p. 40. Cf. Commentary on the Sentences, Bk. III, d. 24, a. 2, sol. 2.) However, Aquinas allows that engaging in this exercise of proving what one believes may render a person’s faith more valuable (meritorious) if “he loves the truth which he believes, he thinks on it and relishes in finding possible reasons for it,” but if done as a condition of believing other articles of faith, it renders that faith less valuable or meritorious. (ST II-II, q. 2, a. 10 and Replies to objections 1 and 2)
On the other hand, Aquinas, describes how it is possible for different sciences to know a single truth both philosophically and theologically and likens this situation to knowing the same physical fact through different natural sciences or by different rational perspectives. As we noted before, Aquinas teaches that philosophy and theology are distinguished by having different intellectual lights, i.e., principles and subject matters. He says, however, that they may each know the same truths in differing manners, as other purely natural sciences do.
Sciences are differentiated according to the different ways that things are knowable. For the astronomer and the physicist both may prove the same conclusion, for instance that the earth is round: the astronomer by means of mathematics, i.e., abstracting from matter, and the physicist by means of matter itself. Hence nothing prevents the things which philosophical disciplines teach by the light of natural reason being the same as what another science [theology] teaches according as they are known by the light of divine revelation.
ST I, q. 1, a. 1, reply 2
Clearly, Aquinas is writing about these various sciences in general as organized bodies of knowledge, but what he teaches here would seem to apply to the sciences as habits of knowing in the souls of practitioners of these disciplines. So, just one and the same thinker can engage in both sciences of astronomy and physics, and thus know the truth of that the earth is a globe mathematically and materially (through the shadow the earth casts during a lunar eclipse), though admittedly not at the same time, so too, one single thinker can know philosophically that God exists and believe the same on the basis of revelation. Étienne Gilson, whose views we will examine in more detail below, seemed convinced that Aquinas would admit as much, based on what people are bound to believe for salvation. “According to Thomas Aquinas, everybody is held explicitly and always to believe that God is, and that he aims at the good of man.” (Étienne Gilson, “What is Christian philosophy?” in A Gilson Reader, A. Pegis, ed., (Image Books 1957) pp. 181-82, and p.190, n 4.) He then cites Aquinas in Disputed Questions on Truth, q.14, a. 11: “Therefore, everyone in every age is bound explicitly to believe that God exists and has providence over human affairs.” Thus, this obligation would continue to apply to the Christian philosopher who has proven rationally (to himself, at least) that God exists and cares for human affairs.
Wippel comments:
Gilson observes that “there is no reason to think that Thomas is rejecting his other thesis that one cannot believe and know the same thing at the same time.” … As Gilson sees it, God’s existence must be accepted on faith by those who have not yet attained to demonstrative knowledge of it. … Then he goes on to suggest that it might be compatible with Thomistic teaching to say that in one sense the existence of God as known by us is not identical with the existence of God as believed by us. … For the affirmation of God by faith is specifically distinct from the affirmation of God by philosophical reason. Belief in God is the first real grasp of that God who is the author of the economy of salvation and the first step on the path leading to man’s ultimate supernatural end in the beatific vision.
Wippel, op. cit.. p. 4, fn. 8.
In this vein, George writes, “Aquinas acknowledges that it can be known through natural reason that divine providence governed the world. Still, a person who did know this could believe in the providence of God as revealed by the faith” (George, art. cit., fn. 57, p. 56.) Gilson, Wippel, and George all seem to suggest that one and the same person can, in respect of the preambles to faith, both know by rational demonstration that God exists and is provident of the human race, on the one hand, and believe with religious faith these same truths because, as grace builds on nature, so faith in supernatural revelation adds the perspective that our happiness will be found in knowing and loving Him in heaven, and that attaining this ultimate end is beyond man’s natural ability. (Cf. ST II-II, q. 1, a. 7.)
For Aquinas, it seems after all, that the Christian need not suspend one’s faith while considering, or indeed proving, some religious tenets in philosophy, since the cognition of the same truth takes on different forms as the mind knows it two different ways, by two different ‘lights.’ Furthermore, while as a Christian, such a philosopher has believed and continues to believe on the basis of faith such a tenet, she may know rationally that the argument is sound: that its premises are true, and its form is valid. There is no reason to believe that a Christian’s ability to fairly evaluate philosophical arguments would be affected at all by her faith, and this ability can and should be applied to arguments about any philosophical topic whatsoever.
Whether Aquinas truly or consistently taught that belief is restricted by proof only applies to the preambles to faith. Aquinas presents much more philosophy in his theological works than proofs for God’s existence, even though this is what he is most known for.
Wippel ultimately contends that there really should not be any question that Aquinas wrote genuine philosophy on the basis of natural, rational argumentation in his small works (opuscula) on natural and metaphysical subjects: On the Principles of Nature, On Being and Essence, Commentary on the Book of Causes among others, as well as commentaries on many of Aristotle’s natural works. As such, there is no question that even the non-Christian may benefit philosophically from these works of Aquinas.
[T]he philosophical opuscula are surely philosophical works. Moreover, they are important sources for Thomas’s personal philosophical views. Granted that the De ente, for instance, is an early work, one already finds therein many of the essential features of the mature Thomistic metaphysics.
Ibid., 26
Moreover, even explicitly theological treatises contain extended passages of a purely natural, rational nature.
To the extent that these are self-contained philosophical discussions, one can free them from the theological context and the biblical and patristic references found in their videturs and sed contras and use them as valuable sources for Thomas’s thought. … In sum, therefore, it would seem that any and all of Thomas’s writings, to the extent that clearly employ metaphysical argumentation, may be regarded as legitimate sources for recovering his metaphysical [i.e., purely philosophical] thought.
Ibid., p. 28-29.
Moreover, the subjective, epistemological status of the individual Christian’s beliefs is not what is at issue, but the lights by which two different disciplines proceed. What these two lights are, and how one, theology, may make use of the other, philosophy, without overwhelming it or undermining its rational independence remains to be seen. The only real question is how might explicitly Christian theological works, such as the Summa Theologiae and Summa contra Gentiles, present and contain truly philosophical insights and arguments that do not depend on the revelation that is fundamental to Aquinas’s whole enterprise in writing these works, while remaining true to his intent and self-understanding as a Christian theologian.
Revealed and Revealable
In the first chapter of The Spirit of Medieval Philosophy, Étienne Gilson claims that there is in theological works of Aquinas a true Christian philosophy that has an intrinsic relationship to faith and revelation beyond being related extrinsically, as facilitating religious belief by giving a non-believer rational evidence that Christianity is true, or as corrective of philosophical errors by removing obstacles to faith which allege to “prove” Christianity must be false.
This effort of truth believed to transform itself into truth known, is truly the life of Christian wisdom, and the body of rational truths resulting from the effort is Christian philosophy itself. Thus the content of Christian philosophy is that body of rational truths discovered, explored or simply safeguarded, thanks to the help reason receives from revelation.
Etienne Gilson, The Spirit of Medieval Philosophy, (University of Notre Dame Press 1994), p. 35.
The Christian philosopher asks “whether among those propositions which by faith he believes to be true, there are not a certain number which reason may know to be true” (P. 36) The discovery of what reason can know in and among what faith believes is the birth of philosophy. When the Christian finds among the truths of his faith
…some that are capable of becoming objects of science then he becomes a philosopher, and if it is to the Christian faith that he owes this new philosophic insight, he becomes a Christian philosopher.
Ibid.
The insight provided by faith, then, seems to consist in making available for rational discovery what is susceptible of philosophical investigation in the content of the faith. For Gilson, Aquinas so engages in genuine philosophical arguments proceeding by natural reason, not faith and revelation, wherein the faith of the one considering philosophical arguments need not, nor ever is, suspended. For Aquinas, Gilson argues, philosophy is intrinsically incorporated into his genuinely theological writings because it is virtually or potentially contained within Scripture and revelation (received in faith) which defines the content and method of theology. As Aquinas writes,
Therefore, because Sacred Scripture considers things under the formality of being divinely revealed (revelata), whatever things are revealable (revelabilia) possesses the one formality of the object of this science; and therefore they are included under Sacred Doctrine as under one science.
ST I, 1, a. 3
Gilson claims that Aquinas is here making a distinction between revelata (things that God has actually revealed, e.g., that Jesus is the Son of God, that God is a Trinity of persons) and revelabilia (things which belong to theology but which reason can know). Revelabilia further divides into two classes: those things which God has revealed and which philosophy can prove (e.g. that God exists, that he is all-knowing) and those things which philosophy can prove but which God did not reveal even though they contribute to men attaining heaven (e.g. that the soul is immortal, that there is not one intellect for all humans). (R. E. Houser, “Trans-forming Philosophical Water into Theological Wine: Gilson and Aquinas,” Proceedings of the American Catholic Philosophical Association 69 (1995), p. 105.)
The knowledge which natural reason can attain, God and the blessed (angels and saints) in heaven know, and consequently could have been revealed. Since these naturally knowable philosophical truths are part of God’s knowledge (which encompasses all truth), the theologian has license to engage in philosophy as philosophy. “Thus, related to the knowledge which God has of Himself, and, as it were, glorified by its theological assumption, philosophy eminently deserves the attention of the Christian Doctor….” (Etienne Gilson, The Christian Philosophy of St. Thomas Aquinas, trans. L. K. Shook (New York: Random House, 1956), 14.) Unlike Pelikan who claims that Aquinas included philosophical proofs for God, for example, because Scripture declares on divine authority that such is possible, Gilson sees such proofs as part of God’s knowledge which revelation could have disclosed.
R E. Houser, in examining Gilson’s argument in detail, notes both its logical as well as textual difficulties. First, Houser notes that the logic of the argument “opens theology too wide, for every truth discoverable by the human mind could be revealed by God…” (Houser, art. cit., p. 106.) Gilson, in making mere possible revelation the rationale for philosophy’s inclusion in theology, has no way to keep any of philosophy, or indeed any human science whatsoever, out of theology. Since God knows everything, and he has (or might have) revealed any truth, any truth might be a properly, intrinsically, theological truth. Aquinas himself, however, recognizes the limits and limitations of various sciences, including theology, and does not advocate for all truth being the domain of Sacred Doctrine founded on faith in God’s revelation.
Houser goes on to show that Aquinas’s inclusion of what philosophy knows by natural reason under what God could have revealed (revelabilia) as distinct from what he does supernaturally reveal (revelata) is not a distinction that Aquinas actually makes. Rather it is a product of the Thomistic commentary tradition. (Ibid., p. 106) Houser thus translates ST I, q. 1, a. 3
Therefore, because sacred scripture considers things as they are divinely revealed (revelata), as has been said, all things which are divinely revealable (revelabilia) communicate in one formal aspect of the object of this science.
Ibid., p. 107.
In context, Aquinas makes clear that what is revealable parallels the sensible, and Houser notes, something is sensible when an animal or human has the passive capacity to be affected by an object with actual sense qualities.
Far from separating revelata and revelabilia, Aquinas’s analogy with sensation identifies the two. Sensata and sensibilia do not signify different classes of things, but refer to the same things. They are called sensata because they actually cause cognition, and sensibilia because they are objects of cognitive power. Likewise, revelata and revelabilia do not signify different things but have the same referent – what has actually been revealed by God. Revelata signifies those things which have been revealed in respect of actually having come from the divine author, from the perspective of their efficient cause. Revelabilia signifies things revealed as objects of the knowledge the theologian can have of them.
Ibid.
Thus, the revealable is what a Christian may understand of even a naturally knowable object in light of what God has revealed about its relation to Him. What precisely the relation to Himself that God reveals, and how it applies to philosophical truths, Aquinas develops through the following articles of Question 1 of the Summa. A brief survey of these texts confirms that he does not specify the formal object of theology only in terms of revelation, but also in terms of what he calls the ‘divine light.’
Divinely Revealed
As noted at the beginning of our discussion of the relationship between philosophy and theology, in the very first article of the first question of the Summa Theologiae, Aquinas writes that Sacred Doctrine exists to enable people to fulfill the goal for which God created human beings, vis., to achieve union with God, a goal beyond what reason can grasp (or unaided human effort can achieve) by revealing and informing them what their goal is. So, theology teaches truths about God and how to achieve salvation which no one could discover by natural reason, unless God revealed them. And even naturally discoverable truths “would only be known by a few, and that after a long time, and with the admixture of many errors,” so God revealed these too to allow people to receive salvation “more fittingly and more surely” (et convenientius et certius). Thus, not only is theology characterized by what is in Scripture and revelation which Christians accept in faith, but also the purpose for which God reveals both naturally and supernaturally knowable truth, i.e., for the sake of human salvation. For it is by sharing in this one goal of revelation, more than what revelation itself contains, which makes possible and legitimate for Aquinas the use of genuine rational philosophical knowledge within Sacred Doctrine.
In article 2, Aquinas describes the formality or light of Sacred Doctrine as the knowledge (scientia) that God and the saints and angels in heaven possess this knowledge, held or acquired by direct vision of God himself, and that God subsequently communicates through revelation.
So it is that Sacred Doctrine is a science because it proceeds from principles known by the light of a higher science, namely, the science of God and the blessed. Hence, just as the musician believes the principles handed on to him by the mathematician, so Sacred Doctrine believes principles revealed by God.
Aquinas in Article 3, as we noted above, writes that everything taught in Sacred Doctrine shares in one common formality, that of being divinely revealed and revealable (in Scripture), and in Reply 2 of this article, he again describes the one formality of Sacred Doctrine as revealable.
Similarly, Sacred Doctrine, precisely as a single science, is able to consider, under one rational formal aspect, namely insofar as they are divinely revealable (sunt divinitus revelabilia), objects which are treated by different philosophical sciences.
Finally, in Article 5, Reply 2, Aquinas writes that Sacred Doctrine “accepts its principles not from other sciences, but immediately from God through revelation.”
Divine Light
Aquinas also describes the one formality that unites Sacred Doctrine as one science, not in terms of revelation, but of vision and divine light.
In Article 3, Reply 1, Aquinas describes this formality as the aspect of relating to God in himself and as he is creation’s origin and goal.
Sacred Doctrine does not teach about God and creatures equally, but about God primarily, and creatures only so far as they are referrable to God as their beginning or end.
In Article 4, Aquinas describes the formality without mention of revelation:
Sacred Doctrine, being one, extends to things which belong to different philosophical sciences because it considers in each the same formal aspect, namely, so far as they can be known through divine light.
Aquinas says in Article 6 that the knowledge of God that Sacred Doctrine attains is of two sorts: First “it treats of Him … as He can be known through creatures…” This sort of knowledge is “what the philosophers knew” (quod philosophi cognoverunt). Second, Sacred Doctrine treats of God “so far as He is known to Himself alone and revealed to others.”
In Article 7, the description of the formality of Sacred Doctrine does not mention revelation, but is given again in relation to God:
But in Sacred Doctrine all things are treated under the rational aspect of God, either because they are God Himself, or because they are referred to God as to their beginning and end.” and “so far as they are ordered to God.”
As this brief survey of these texts shows, and as Houser convincingly argues, revelation as such, whether explicit in Scripture or virtual and implicit in what could be revealed, is not (or is not simply (simpliciter)), in fact, the unifying principle of Sacred Doctrine for Aquinas. It is rather the goal, or end to which God intends revelation to lead, a goal ultimately realized in heaven in the happiness of knowing God Himself and seeing Him face to face. Throughout his career Aquinas taught that serving the end of theology, and that alone, is what justifies making use of philosophy, and that that use is made within theology itself. (Ibid., p. 111.) All teaching undertaken for this purpose, which very purpose itself is something that God reveals, places that teaching formally within Sacred Doctrine. This applies, too, to theology’s use of philosophy: by thus sharing in the end of theology, philosophy is incorporated into theology and the theologian as such is able to make legitimate use of philosophy.
It is in terms of sharing in the end of revelation, that Aquinas, as we saw before in his Commentary on De Trinitate q. 2, a. 3, Reply to Objection 5, likens philosophy in the service of the faith to transubstantiated wine. “Those who use the works of philosophers in sacred doctrine, by bringing them into the service of faith, do not mix water with wine, but rather change water into wine.” Houser explains:
What has transubstantiated philosophical water into theological wine is ‘service to faith.’ … What makes all scientific conclusions fully theological is that they lead to, not where they come from; their end not their premises.
Ibid.
Even philosophical science which proceed by natural reason can also be theological if they are of service to faith and lead or are directed to the goal which, and for which, God revealed his own science of Himself. That goal is, in fact, God Himself, by which humans attain salvation and eternal happiness in the contemplation of God’s own essence in the Beatific Vision.
Revelation through Scripture (whether revealed (revelata) or revealable (revelabilia)) is not the most central aspect to the subject of Sacred Doctrine. Rather originating from and being oriented toward God is the formal aspect under which Sacred Doctrine focuses on whatever it considers. Things besides God are known by Sacred Doctrine in terms of their relation to Him. Nevertheless, revelation is still important for Sacred Doctrine, but not because everything it deals with is either actually or virtually contained in it. Rather, for Aquinas, Sacred Doctrine shares in the one formal aspect by which revelation itself operates, i.e., the formality of what Scripture contains and why, which is to disclose God as man’s last end, a goal that exceeds what reason alone could discover.
Aquinas thus brings the lower philosophical sciences into theology without overwhelming the light of reason by which they know. In themselves, philosophical sciences know things for their own sake (speculatively) or for the sake of human action, and natural human happiness (Aristotle’s fulfillment or flourishing(eudaimonia)). But such natural knowledge can be taken up into theology insofar revelation illumines it by referring it to God as origin and goal, according as He is known to Himself alone, shared in by the blessed in heaven, and which relation He reveals in Scripture for the salvation of people.
Handmaids: Preserving the Integrity of Philosophy
Yet, while serving the end of faith and theology may make philosophy useful to the theologian, it also seems to overwhelm the natural, rational character of philosophy, transforming the philosophy so used into theology, and making it fit for no one who does not share that same faith. For Aquinas, however, coming to share only in the end of theology, not being explicitly or implicitly revealed or revealable, actually preserves the integrity of philosophy within his theological works and makes it useful and informative to those non theists and non-Christians.
The end of an argument does not affect the principles from which it flows. Purely rational principles make the arguments of Christian philosophy philosophical; their faith-given end makes them theological. This is what ensures that the philosophy within theology is fully philosophical “in essence” and “in method,” while fully theological in purpose.
Ibid., p. 112.
Thankfully, Thomas Aquinas elaborates on the relationship of philosophy to theology in a way other than as transubstantiated water into wine, a way that preserves the integrity and autonomy of philosophy when considered and used by his students who do not share his Christian faith. In his Sentences commentary, Aquinas likened theology’s use of philosophy to a feudal lord directing his vassal, and to ordering and subordinated sciences and arts.
[Sacred Doctrine] itself makes use of all the other sciences in their service (obsequium) to it, as though they were its vassals. This is clear in all the ordered arts, where the end of one is under the end of another. For example, the end of the art of ointments, which is the production of medicines, is ordered to the end of medicine, which is health; this is why the physician directs the ointment-maker and uses the ointments he makes for his own end. So too, since the end of the whole of philosophy is under the end of theology, and is ordered to it, theology ought to direct other sciences and use what is taught in them.
Commentary on the Sentences, Book I, Prologue, q. 1, a. 1.
Aquinas notes the parallel between the end or goal of the art of ointment making in concocting medicine being subservient to the end of medicine, i.e., health of the body, and the end of theology, seeing God face to face in heaven, using and directing philosophy. (Houser, art. cit., p. 110) There are limits however, to this direction which Aquinas will make clear in other texts that elaborate on this sort of relationship between ordering and subordinated sciences. Even in this text, though, Aquinas seems to recognize that the physician must respect the art of ointment making, and cannot direct the herbalist to produce an elixir that his art deems herbally impossible. Nor can theology direct philosophy to prove what cannot be proven. The subordinated art or science must and can only operate according to reality and the truth of things as they are (and, the theologian knows, as God made them).
In Article 5, Reply to Objection 2 of Question 1 the Summa, Aquinas invokes the same analogy to describe more precisely the relationship between natural and supernatural knowledge in the study of theology. Sacred Doctrine, he says, includes and employs philosophy in the manner that architectonic sciences order and organize others in accomplishing their own larger goals and purposes, e.g., as political theory makes use of military studies. He explains in his Commentary on Aristotle’s Metaphysics the “arts are called architectonic which direct other subserving arts, just as the captain of a ship directs shipbuilders, and the military [directs] horsemanship.” (Book 5, Lecture 1, no. 758.) Thus, Sacred Doctrine takes natural philosophical sciences into itself by directing them to accomplish its own end that lies beyond their ability. Philosophical disciplines thus serve as handmaids to theology.
This science is able to take something from the philosophical disciplines, not as though it requires them of necessity, but only for the greater clarity of what is taught in this science. For it accepts its principles not from other sciences, but immediately from God through revelation. Therefore, it does not depend upon other sciences as higher (than itself), but makes use of them as lesser, and as handmaidens: just as architectonic sciences make use of subservient ones, as the civil [makes use of] military [science].
In his Commentary on Aristotle’s Ethics, Aquinas correspondingly writes that the architectonic science of politics uses arts and sciences subject to it for its own ends, as equestrian art directs bridle-making, or in directing the smith to make knives of a particular kind, presumably for soldiers for the sake of defending the state. (Book I, Lecture 2, no. 26) There are, Aquinas notes, limits on the direction an architectonic science gives to speculative and theoretical sciences such as mathematics, geometry, and presumably philosophy.
But political science does not dictate to a speculative science … about the determination of its proper activity, for while political science may order that some people teach or learn geometry … but not what it should conclude about a triangle, for this … depends on the very nature of things.
Ibid, no 27.
Similarly, while Sacred Doctrine may direct and use philosophical sciences for its own end of attaining the Beatific Vision as an architectonic science like politics, theology would be similarly constrained not to dictate to philosophy what it should conclude about its own proper subject nor the principles and methods it uses to discover truth.
Conclusion
By thus showing that Sacred Doctrine is unified not just as things are revealable (revelabilia) or revealed (revelata) as being implicitly or potential and actually contained in the books of the Bible, but as the divine light shows their relation to God as source and goal, Aquinas incorporates natural, philosophical science into theology, while at the same time respecting its autonomy, guaranteeing the natural has not been overcome or tainted by the supernatural.
Thus, such sciences as Aristotelian natural philosophy and its doctrine of form and matter (see below, Chapter 3) can belong in Sacred Doctrine in Aquinas’s explanation in the Summa that the human soul is the form of a natural organized human body, and that each person has their own intellect (in opposition to the Latin Averroists mentioned above). This is legitimate, not because revelation says it can be naturally known, nor because it could have been revealed. It is legitimate because God has revealed that the things treated in that science are related to God as first originating cause and humans’ last end. So, in seeking to know human beings, Aquinas uses philosophy as philosophy, and understands by the light of natural reason that the human soul is the form of a naturally organized body capable of life. This philosophical truth, though, also supports the theological truth that the soul cannot pre-exist the biological gestation of a suitable body (although each human soul can survive the death of its body and is naturally immortal). But the arguments are also theological since the theologian, by the divine light given in revelation in Scripture, sees (as exceeding the grasp of reason) that human persons are related to God as their first cause and last end, and the philosophical knowledge itself is also so related.
And again, as Aquinas stated in his Commentary on Boethius’s On the Trinity, theology may use philosophical/natural reasoning if and only if it is true, since God is the source of all truth, and any truth is referrable to him as source, form, or end. This means that a philosophical conclusion that does not accord with Christian teaching must be false. In this way, Sacred Doctrine is said not to prove the principles of other sciences, but to judge them, especially the teachings of philosophers. It remains to philosophy as such, even though as part of a theological enterprise (as in the Summa, et al.) to present true conclusions by the light of natural reason, and to discover the error, or the non-necessity, in false ones.
Substantially revised December 3, 2024.
References updated January 20, 2025
For a discussion of this issue with respect to the existence of God, see the article on Natural Theology.
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