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“That There Were True Things To Say:” The Scandal of Philosophy and Demonstrating God's Existence in Thomistic Natural Theology

Published online by Cambridge University Press:  01 January 2024

Brian Jones
Brian Jones*
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University of St. Thomas, Philosophy 3800 Montrose Houston, Texas, United States, 77006-4626, Houston, United States
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Original Article
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New Blackfriars , Volume 95 , Issue 1058 , July 2014 , pp. 412 - 429
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Copyright © 2013 The Author. New Blackfriars

Philosophers have been calling attention to the fact that the greatest defenders of reason in the modern era have been those men that have occupied the Chair of St. Peter.Footnote 1 Catholics of course do not take surprise, let alone offense, to such a claim. The necessary complementarity of faith and reason is recognized and upheld by the ordinary believing Catholic, even if denied by certain Christians. The Cartesian turn in modern philosophy has purported that a serious philosopher, believer or not, must put aside his antecedent beliefs. Only then, through “pure reason,” can authentic philosophy begin. This epistemic tumor has not born destructive tendencies only within professional philosophy, but has also become the very characteristic that has befallen modern man. Pope John Paul II has laid a very serious office on the philosopher and his vocation in light of this philosophic milieu: “philosophers have to verify the human capacity to know the truth, to come to a knowledge which can reach objective truth by means of that adaequatio rei et intellectus to which the Scholastic Doctors referred.”Footnote 2

Along with his predecessors, Pope John Paul II points to Thomas Aquinas as the philosopher (and theologian) exemplar. Aquinas taught that the truths man could know are not just the heritage of the philosophers, but of anyone that is born into the human race. Philosophic truths are often based upon what one already knows through his experience of the world around him. One need not be a professional philosopher to discover this. In fact, being a professional philosopher could be detrimental to this realization.Footnote 3 The certitude of man's confidence in knowing the world outside of his own mind, and the confidence that what we know about the external world is actually true, is the great patrimony of perennial philosophy. The scandal of the history of philosophy “was not that so many said false things so much as that they have all believed there were true things to say.”Footnote 4

One of the many true things to say regarding our knowledge of the way things are is that “God exists.” The existence of God is a truth that can be known by reason without the aid of Revelation. That God can be known outside of His revelation is something Aquinas attributed as the great achievement of Aristotle and Plato. This philosophic enterprise is the work of Natural Theology. It is called Theology because it considers questions pertaining to God, and Natural because it discerns what reason can know apart from Revelation.Footnote 5 The task at hand in these reflections is to defend St. Thomas Aquinas' account of Natural Theology. In the first place, I will examine the texts that Natural Theology is grounded upon, namely, whether God's existence is known to us per se and whether His existence can be demonstrated. After establishing this foundation for the truth of Aquinas' Natural Theology, I will turn to some objections of this project, most notably in the work of Alvin Plantinga. In the final part of the paper, I hope to provide a thorough and succinct Thomistic reply to Plantinga's objections.Footnote 6

I

In the De Veritate, q.10,a.12,St.Thomas asks whether God's existence is known through itself by the human mind. He purports that there are three principle objections to this question. In the first place, the Jewish philosopher Maimonides says that God's existence (Deum esse) is not known through itself, nor through a demonstration, but can only be accepted upon faith. The feebleness of the reasons proposed fall short of being able to demonstrate that God exists.Footnote 7 The second objection put forth by Avicenna is that God's existence is not known in itselfFootnote 8 (per se notum), but is known through a demonstration. The final objection comes from Anselm, who thought God's existence is known through itself, insofar as, no one can understand interiorly (cogitare interius) that God does not exist, even though one can say this exteriorly, and understand interiorly the words by which it is said.Footnote 9 Thomas rejects Maimonedes position as manifestly false because God's existence has been proved by irrefutable arguments (demonstrationibus irrefragabilibus) even by philosophers. Avicenna and Anselm's position are considered true in a certain respect. Aquinas proposes making a necessary distinction between a thing being known in its own right in two ways: in relation to itself and in relation to us.Footnote 10 He states that something can be known in itself, but not in relation to us. Demonstrations from effects would be necessary then to know something known in itself, but not to us.

Thomas goes on to distinguish the conditions necessary for a proposition known in its own right. A proposition is known in its own right when the predicate belongs to the very nature of the subject, such that the predicate cannot be thought without the subject being manifest in it. Some things are known through themselves by everyone, such as when propositions have subjects of which the nature (ratio) is known by everyone. For example, that every whole is greater than its part. Other things are known only by those who know the very definition of the terms.Footnote 11 Thomas finds the support for this claim in Boethius' De Hebdomanibus, where he draws a distinction between “two kinds of common conceptions.” The first is common to everyone, such as “if equal amounts are subtracted from equal things, what remain are equal to each other.” The second is common to the learned alone, such as “incorporeal things are not in a place.” Common people are unable to transcend the consideration of the imagination that incorporeal beings are not in a place.Footnote 12 Since the being (esse) of every creature is other than its quiddity (or whatness), being (esse) is not perfectly within the nature of creatures. Therefore, a creature's being is not known through itself and according to itself. However, in God's very being is included the nature of His quiddity, because what God is and that He is is the same (idem an est et quid est). Hence, God's being is His essence, and is known to Himself, but it is not known to us. This requires that His existence be shown through demonstration.Footnote 13

In Book I of the Summa Contra Gentiles, chapters 10–11, Thomas seeks to respond to those persons who assert that God's existence is known in itself, and that His existence could not be demonstrated. The Anselmian argument is that propositions are known in themselves immediately once the terms are known. Once a person knows what a whole and a part is, he immediately knows that a whole is greater than a part. The question of God's existence is of this kind, since the name God is that than which a greater cannot be thought. Since this idea of God is already in the mind, it must exist in reality because that which exists in the mind and in reality is greater than that which exists only in the mind. Therefore, God's existence is known in its own right, even by us.Footnote 14

The second argument is similar to the first, in that since God is the greatest conceivable being, He cannot be thought not to be. From the very definition of the name God it cannot be thought that He does not exist. The third argument is that propositions are most known when the predicate is included in the very definition of the subject. Since it has been established that God's being (esse) is His essence, the answer to the question “What is He” and the question “Whether He is” is going to be the same. Therefore, God's existence is known in its own right, even to us. The fourth argument comes from John Damascene, who purports that man naturally knows God because he naturally desires God as his ultimate end (finis ultimus). The fifth and final argument opines that just as the sun is the principle of all visible perception, so too the Divine light is the principle of all intelligible knowledge. Considering that the Divine light is that in which intelligible illumination is found first and to the highest degree, it is clear that the existence of God is known in its own right and does not require demonstration.Footnote 15

It is interesting that Thomas begins his response to the aforementioned objections by recalling that custom and upbringing can lead us to take God's existence as given, as known to us without need of demonstration. This results in a failure to distinguish between something known in its own right and that which is known to us. Man is not able to conceive what God is, and therefore we are unable to know Him as He knows himself. Responding to Anselm's objection, Thomas points out that as soon as we know the meaning of the name “God,” it does not follow that we immediately know that “God exists.” Thomas provides two reasons for this. First, it does not necessarily follow that all who admit of God's existence think that God is that than which a greater cannot be thought. Secondly, the definition of God as that than which a greater cannot be thought does not prove that there exists in reality something than which a greater cannot be thought. Even if one were to agree that this is what the term “God” signifies, it is not necessary that there should be something in reality that corresponds to this description. For the thing and the meaning of the name must be posited in the same manner. From the fact that one understands the meaning of the term “God,” it follows only that God exists in the mind.Footnote 16

Replying to the second argument in the body of Ch. 10, Thomas says that one who thinks that God can be thought not to be arises from the weakness of man's intellect, which is incapable of seeing God's essence, but must demonstrate His existence only by way of his effects.Footnote 17 In a similar manner, the response to the third and fourth objections for Thomas is simply that only for the Blessed in Heaven, who see the Divine essence, is it supremely manifest that God's existence is known to us. We can only come to knowledge of His existence through His effects. Regarding man's natural desire for God, Thomas says this desire is a certain likeness of the divine goodness. What man knows is not God's essence known to Himself, but only a certain likeness of God. So too, man discovers this divine likeness in His effects visible to us.Footnote 18 Finally, contrary to St. Augustine, Thomas posits that things can be known without knowing God. While it is true that God has placed the principles of knowledge in us, we can know things even without knowing Him. Otherwise, one could only know something in so far as God was known, which would make such things as the developments in the field of science or any branch of knowledge practically impossible.Footnote 19

In the Summa Theologiae, q. 2, a. 1, one finds a final presentation of the necessity of demonstrating God's existence. Thomas draws a distinction between the two ways that something can be known per se: in its own right (secundum se), but not to us (quoad nos), or both in its own right and to us. When a proposition contains the predicate in the very definition (ratio) of the subject, then it is known per se. If the definitions of the terms are known to everyone, then everyone will know the proposition in itself. Thomas, following Aristotle, says that this is the case with the first principles of demonstration, i.e., the principle of non-contradiction, and whole and part. However, not every proposition is known in itself. Drawing from Boethius' De hebdomanibus, Aquinas argues that the proposition considered would not be known in itself (per se) for those who are unacquainted with the predicate and subject. God's existence is known in itself, where the predicate is the same as the subject, since God is His own esse. However, since we do not know the real definition of God, man does not know God's existence as He knows it. Therefore, the existence of God must be demonstrated by means that are more known to us, namely, through his effects.Footnote 20

Responding to the two primary objections, Thomas argues first against John Damascene's teaching that knowledge of God is instilled in all man naturally. The knowledge of God is instilled in man in a general and indistinct way, but this is not to know without qualification that there is a God. I could know that someone is approaching me on the street, but that does not mean that I know it is Peter who is approaching. Thomas also takes up the Anselmian argument that God's existence is known per se even to man since He is that than which a greater can not be thought. Granted that a person may think Anselm's definition of God is correct, it still would not follow necessarily that what he thinks is signified by ‘God’ actually exists in reality and not just in the mind alone. For even those who say, “God does not exist” do not believe that than which a greater cannot be thought actually exists in reality.Footnote 21

In all three of the texts examined thus far, Thomas affirms that God's existence is known per se, but not to us. Given that we have no quidditative knowledge of God, it is necessary that His existence be demonstrated through His effects. As a result of this, Thomas is not concerned that someone can affirm that God exists even though he does not know what God is. Seeing as this quidditative knowledge of God is absent, and that God's existence is not known in itself to us, Thomas thinks it is possible that one could think that God does not exist. The doctrine of Thomas' natural theology is grounded in the preceding discussion of his teaching in affirming that God's existence cannot be known apart from a demonstration. One can hear the skeptic smirking at this point: if God's existence is not known per se, and requires a demonstration, then what in fact is being demonstrated?

Following Aristotle, Thomas understands that scientific questions are to be answered by demonstrations.Footnote 22 Science is causal knowledge: when one knows scientifically one understands why something is the way that it is. In a demonstrative proposition it is the middle term that explains why one should conclude that a given predicate belongs to a given subject.Footnote 23 Thomas distinguishes two kinds of demonstrations. The first kind is a demonstration propter quid, which is through things that are prior absolutely, a priori. The second kind is a demonstration quia, which is through things that are prior with respect to us, a posteriori. An excellent a posteriori example would be the practice of medicine, whereby the physician looks to the somatic effects in the body to lead him back to discovering the cause. A quia demonstration is through an effect that is going to be more apparent to us than the cause. In the case of God, we do not have a real definition of Him because we are unable to know His esse. Thomas observes that one must take a nominal definition (quid significat nomen) and not a real definition (quid est) when we demonstrate God's existence. Since we have no knowledge of the cause, the effect indicates the cause to us,Footnote 24 and the middle term takes the place of the real definition of the cause.Footnote 25 From this, Thomas concludes that the nominal definition of God actually leads one to affirm the truth that God exists.

In order to reject the idea that God's esse is known to us, Thomas further clarifies what we are attempting to do in a quia demonstration. Since we cannot know what God is (quid sit), but rather that He is (an sit), it must be that God's esse is not the same as what it is to be God (eius quod quid est), i.e., not the same as His ‘what-ness’ (quidditas) or nature.Footnote 26 In reply to this, Thomas says esse can be taken in two ways. It can signify the act of being (actum essendi), or it can signify the propositional composition that the mind forms by joining a predicate to a subject. If esse is taken in the first way, then we cannot know that God exists since His esse is His essence. However, esse taken in the second way, we can know that God exists because the composition formed in the mind is known to be true.Footnote 27 Since we know this is true by reasoning from effects to cause, then Thomas has illustrated that in a quia demonstration for God's existence, one has attained a new form of knowledge that he previously did not have.Footnote 28

II

The Thomistic account of natural theology is a philosophic enterprise that fundamentally seeks to show that God's existence can be known and demonstrated by man through reason. Some Christian philosophers have rejected natural theology as being in opposition to the life of faith, professing that belief in God does not require a “proof” or “demonstration.” The most notable critic of natural theology is Alvin Plantinga. In what follows, I will analyze Plantinga's argumentsFootnote 29 for rejecting natural theology in light of what has been discussed above, and respond to his criticisms.

Plantinga seeks to develop and build upon critiques of natural theology offered by some of the Protestant reformed thinkers. He begins his essay noting that while some reformed thinkers endorsed proofs for God's existence, the overarching reformed attitude ranged “from indifference, through suspicion and hostility, to outright accusations of blasphemy…this stance initially seems puzzling…what exactly, or even approximately, do these sons and daughters of the Reformation have against proving the existence of God? What could they have against it? What could be less objectionable to any but the most obdurate atheist?”Footnote 30 Plantinga seeks to answer these questions by examining the objections to natural theology in the works of two representative Reformed thinkers: Herman Bavinck and John Calvin.Footnote 31

Plantinga begins his treatment of the Reformed thinkers by quoting Bavinck: “Scripture…does not make God the conclusion of a syllogism, leaving it to us whether we think the argument holds or not…both theologically and religiously it proceeds from God as the starting point.”Footnote 32 The existence of God can be seen to rely on these supposed proofs, but this would be rather dangerous: “the so-called proofs are by no means the final grounds of our most certain conviction that God exists: this certainty is established only by faith, i.e., by the spontaneous testimony which forces itself upon us from every side.”Footnote 33 According to Bavinck, the project of natural theology proposed by Aquinas ought to be rejected, particularly for the Christian, “since Christians do not need such arguments. Don't need them for what?”Footnote 34 Plantinga provides two answers to this question. First, arguments are not “the source of a believer's confidence in God, for the believer does not believe in God on the basis of arguments.Footnote 35 Secondly, arguments are not needed “for rational justification; the believer is entirely within his epistemic right in believing that God has created the world, even if he has no argument at all for that conclusion. The believer does not need natural theology.”Footnote 36 For Plantinga, a person's belief in God is perfectly rational even if he knows of cogent argument for it, even if there is no such argument.

Regarding the first claim, Plantinga does not make clear what he means when he says that arguments or proofs are not the “source” of a believer's confidence in God. While this is certainly true in the case of a number of believers, it does not follow for every believer. A person that moves from atheism to agnosticism, or agnosticism to theism, it would be true that the source of his belief could be an argument or the re-examination of a proof that had not been studied in great detail. Another concern with this objection seems to be that it is not an argument against the doctrine of natural theology, but rather against one specific application of it. The fact that a person's beliefs “about the existence and nature of atoms do not, in general, have their source in arguments or proofs has no tendency to denigrate, much less to undercut, atomic physics.”Footnote 37 Belief in God, as Aquinas mentions, does not require a study of philosophy, or that one in fact be a philosopher. The distractions of life, the perseverance required, and the lack of ability often prevent man from seeking answers to the ultimate questions. For this reason, God has revealed the answers to these philosophic questions in order that we may more firmly root our faith in the certitude of God's authority. While belief does not require the dependence on proofs for God's existence, Plantigna does not stress the necessity of seeking further understanding in faith. He also fails to mention that natural theology, as an activity of the theoretical intellect, seeks to know a truth that it previously did not concerning God's existence independently of revelation.

Plantinga's second claim, that rational justification is not required for believing that God's existence is true. This idea not only provides no solid argument against natural theology, it also purposes a troubling assent to fideism. The reliability of proofs for God's existence is a reasonable question, and not one to be immediately discarded. If a non-believer approached me to ask what evidence there was for believing in God, I would be naïve if I uttered: “there is no evidence. I just believe it.” Dialogue with this inquirer has just ended, and I have merely affirmed his previous inclinations that believers rely on nothing but sheer blindness. A believer may not have to rely upon proofs for God's existence, but this is no more an argument against natural theology than a philosophy of mathematics when balancing his check book-which is no objection to a philosophy of mathematics.Footnote 38 Furthermore, establishing that God exists through the exercise of reason can also seem to be a help for the believer when he experiences doubts or stumbling blocks in his faith. To recall that it can be established through the created things of the universe that God exists can surely aid a believer in rekindling his faith in moments of darkness.

Plantinga highlights three final claims from Bavinck's rejection of natural theology. Following a number of historically confusing and distorted attempts at theistic proofs (mainly from Kant), Bavinck concludes that we cannot come to a knowledge of God's existence on the basis of demonstration, since the project of natural theology just does not work. Plantinga furthers this point when he says that “the Reformed objectors need not suppose that natural theology is of no use…if there were good arguments for the existence of God, that would be a fact worth knowing in itself.”Footnote 39 As was mentioned previously, this argument is not an argument against natural theology as a whole. The failure of particular proofs for God's existence does not dismantle the project of natural theology. Aquinas frequently uses Anselm's “that than which a greater cannot be conceived” as an example of an argument for God's existence that does not work. He does not conclude, however, that this is the end of the philosophic pursuit of proving that God exists.

The next claim that Plantinga takes from Bavinck is this: “Scripture proceeds from God as the starting point, and so should the believer. There is nothing by way of proofs or arguments for God's existence in the Bible; that is simply presupposed. The same should be true of the Christian believer then; he should start from belief in God, rather than from the premises of some argument whose conclusion is that God exists. What is it that makes those premises a better starting point anyway?”Footnote 40 When a believer approaches Scripture, he is granting that the articles of faith, which have been revealed, are in fact true because of the One who has revealed them as such. Plantinga's point does not seem to pose any problem for a believer who practices natural theology. It is not the case, however, that there is nothing by way of proofs for God's existence in Scripture.Footnote 41 In Romans 1:20, one reads “for the invisible things of him, from the creation of the world, are clearly seen, being understood by the things that are made.” Furthermore, the First Vatican Council dogmatically proclaimed that God, the beginning and end of all things, could be known with certitude by the natural light of reason through the created world. As a possible objection, Plantinga's point is merely a religious one, and not a legitimate attempt to refute the claims of natural theology as a philosophic discipline.

Plantinga's final argument against natural theology from Bavinck is that belief in God “resembles belief in the existence of the self and the external world-and, we might add, belief in other minds and the past. In none of these areas do we typically have proof or arguments, or need proofs or arguments.”Footnote 42 For Plantinga, and the Reformers objections to natural theology, belief in God is “properly basic.” Belief in God is not dependent upon any other beliefs that one holds. Since proper basicality does not depend upon any other beliefs, then it also does not need rational justification for it to be believed. It is perfectly reasonable to believe in God's existence even if no reasonable argument can be given, and this may also entail that no such argument does exist. Acknowledging “I exist” as properly ‘basic’ would not seem to be epistemically equivalent to saying that “God exists.” Denying the existence of the self would seem to be more of an absurdity than denying that God exists, since His existence does require a demonstration. As for our belief in the external world, its rejection (similar to a rejection of the existing self) is a rather modern phenomenon. It was only the subjectivist turn in philosophy that arguments against an existing external world and its ability to be known have risen. Outside philosophy we certainly do not “need arguments supporting our belief in the external world, but that's because formidable skeptical arguments challenging that belief arise only within philosophy.”Footnote 43

After Bavinck, Plantinga turns to John Calvin's objections to natural theology. According to Calvin, God has implanted in us an innate tendency or disposition to believe in Him. There is present within the human mind this natural instinct, an awareness of the divinity that Calvin calls the sensus divinitas. Although the impious seeks to flee from God, he is unable, and “this is abundant testimony that this conviction, namely, that there is some God, is naturally inborn in all, and is fixed deep within…From this we conclude that it is not a doctrine that must be first learned in school, but one of which nature itself permits no one to forget.”Footnote 44 Plantinga states that our unnatural sinful condition is the reason many find belief in God difficult or absurd. Even though this natural inclination to believe in God is suppressed, “God daily discloses himself in the whole workmanship of the universe, and as a consequence, men cannot open their eyes without being compelled to see Him.”Footnote 45

Following Calvin, Plantinga thinks that one who does not believe in God is in “an epistemically substandard position-rather like a man who does not believe that his wife exists, or thinks she is a cleverly constructed robot, and has no thoughts, feelings, or consciousness.”Footnote 46 If our disposition to believe in God is universally present, and we cannot open our eyes without seeing Him, then the atheist is not just in a substandard epistemic condition, but an impossible one.Footnote 47 Believing in God by the mere opening of the eyes would seem to mean that God's existence would be so obvious that even those who did not seek Him would find Him, which clearly contradicts Scripture and the doctrine of natural theology. Plantinga continues that the prophets and apostles “do not dwell upon rational proofs. Rather, they bring forward God's holy name, that by it the whole world may be brought into obedience to Him…we ought to seek our conviction is a higher place than human reasons, that is, in the secret testimony of the Spirit.”Footnote 48 The project of natural theology is not needed for the Christian because proofs are not the source of his confidence in believing. This claim is more of a religious awareness regarding the discipline of theology, and not a substantial philosophic objection to natural theology.

III

The Reformed objections to natural theology that Plantinga supports and seeks to develop have fallen short of their intended aim. The arguments put forth have not built a formidable philosophical objection to natural theology, but have led to an inchoate and misguided religious objection. Considering the criticisms I have just offered in light of Plantinga's “reformed epistemology,” and the insights from the first part of this paper, I would like to provide one final critique of Plantinga's objection to natural theology that is architectonic to his project. When reviewing Plantinga's concerns with natural theology, particularly the idea of proofs for God's existence, it becomes clear that he has neglected to distinguish, nor attempted to distinguish, belief and knowledge. This distinction is fundamental for both natural and revealed theology. Obscuring or overlooking the necessity of this distinction can lead one to accept Plantinga's perspective or one similar to it. For the final part of this paper, I will briefly analyze Aquinas' account of the differentiation between faith and knowledge.

Aquinas begins his discussion of belief by drawing three important distinctions between doubt, opinion, and knowledge.Footnote 49 Knowledge can be defined as a rejection of the contradictory opposite of a given proposition. If I know something, in the strict sense, then I reject its contradictory opposite as being false. When I am more inclined to accept one part of proposition as true, but still hold its contradictory opposite as being possibly true also, my lack of total acceptance to one part results in an opinion. Sometimes I am not inclined to either part of a proposition, where there is a fluctuation between two parts of a contradiction, and this would leave me into a state of doubt.Footnote 50 For Aquinas, belief (which is located between knowledge and opinion) is assent to a truth or collection of truths on the authority of another. In a sense, belief is nothing other than a trust in the competency of another as an authority. When I taught my middle school students about the elementary truths of biology, they believed what I told them was true. They did not have knowledge of the material themselves. Hence, if they did have the knowledge I possessed, they would not have come to listen to my constant rambling.

As an infused habit of the mind by which eternal life begins in us, faith is that which makes the intellect assent to things that are not apparent.Footnote 51 The object of faith is that which is absent from man's understanding, since his reason cannot lead him to see the things that pertain to faith.Footnote 52 The doctrines of the Trinity, Incarnation, and the forgiveness of sins are such that they are proposed to man for belief. I am unable to understand these truths because they exceed the scope of natural reason. When my former students approach me and tell me that they want to be chemists or engineers, they often remind me that they finally have come to understand what I taught them. Although I frequently confused them because of my own inabilities, they recognized that they no longer believe what I told them: they know it themselves. This is why Aquinas concludes that it is impossible to have faith and knowledge about the same thing and at the same time.Footnote 53

It is interesting that Thomas proposes two ways to understand the object of belief. In one sense, what is proposed exceeds the intellectual capacity of men in this life, such that they cannot be known but only believed. On the other hand, there are some beliefs that can be known in this life, and these are established of God by means of demonstrations, i.e., that God exists, or is one, or has no body. There is nothing that prevents proofs from being known scientifically by some, while for others, these same proofs can be proposed for belief. This point displays the clear necessary relationship between faith and reason. The proposition, “God exists,” can be proved by a demonstration, and is therefore not an article of faith, but is presupposed before the articles. For Thomas, these are known as the preambula fidei, or the preambles of faith.

IV

From the preceding remarks, we can see that Thomistic natural theology has provided an indelible mark upon the history of philosophy. When natural theology is distorted, or even rejected, the result is a corruption of both faith and reason. For if the project must be rejected by believers, this disjunction will make it challenging to establish why it would then only be true for the non-believer. In the end, the believer who is also a philosopher need not feel threatened by affirming that God's existence can be shown apart from Divine Revelation. The Catholic philosopher need not do away with his antecedent convictions: he is in an ultimately better position than the non-believing philosopher since the Catholic does not “import into his philosophy any premise or conclusion from his faith, but he knows there are conclusions in philosophy which could be untrue because they would contradict his faith.”Footnote 54 This is a great consolation in philosophizing, since it enables reason to be more fully itself. That God's existence can be demonstrated reaffirms the perennial philosophic truth that man's reason is capable of knowing that which exists outside the mind, and knowing it as true.

References

1 See Alfred Freddoso's “Fides et Ratio: A Radical Vision of Intellectual Inquiry,” (paper presented at the annual meeting for the American Maritain Association, October, 2000).

2 Fides et Ratio, Encyclical Letter of Pope John Paul II, 1998; #82.

3 Hence the reason for Chesterton's well-known remark that Thomism is nothing other than “common sense.”

4 McInerny, Ralph, Characters in Search of Their Authors: The Gifford Lectures 1999–2000 (Notre Dame: University of Notre Dame Press, 2001), 41Google Scholar.

5 Ibid., 5.

6 I do not purport that natural theology is only concerned with demonstrating God's existence, for this idea would be distorting Thomistic natural theology. For my purpose, I only deal with demonstrations for God's existence because it sets the foundation for everything within the discipline of natural theology. For other excellent works on Thomistic natural theology, see Elders, Leo, The Philosophical Theology of St. Thomas Aquinas (Leiden, New York: E.J. Brill, 1990)CrossRefGoogle Scholar; Scheltens, D., “Reflections on Natural Theology,” International Philosophical Quarterly 11 (1971): 75–86CrossRefGoogle Scholar; John F. Wippel, “Philosophy and the Preambles of Faith in Thomas Aquinas,” (paper presented at the meeting of the Pontifical Academy of St. Thomas Aquinas, Rome, June 20–22, 2008): 38–61; White, Thomas Joseph, Wisdom in the Face of Modernity: A Study in Thomistic Natural Theology (Ave Maria, Florida: Sapienta Press, 2009)Google Scholar.

7 See De Veritate, q. 10, a. 12, Responsio: Dicendum, quod circa hanc quaestionem invenitur triplex opinio. Quidam enim, ut Rabbi Moyses narrat, dixerunt quod Deum esse non est per se notum, nec etiam per demonstrationem scitum, sed est tantum a fide susceptum; et ad hoc dicendum induxit eos debilitas rationum quas multi inducunt ad probandum Deum esse.

8 I have intentionally translated per se notum as “known through itself” because this definition is more clear and easier to understand than the vague term “self-evident.” I am grateful for Dr. Christopher Martin and Dr. Alfred Freddoso with assistance in helping me to understand the importance of translating per se notum as such.

9 See De Veritate, q. 10, a. 12, Responsio: Alii vero, ut Anselmus, opinantur quod Deum esse sit per se notum, in tantum quod nullus possit cogitare interius Deum non esse; quamvis hoc possit exterius proferre, et verba quibus profert interius cogitare.

10 See ibid: Prima quidem opinio manifeste falsa apparet. Invenitur enim hoc quod est Deum esse, demonstrationibus irrefragabilibus etiam a philosophis probatum; quamvis etiam a nonnullis ad hoc ostendendum aliquae rationes frivolae inducantur. Duarum vero opinionum sequentium utraque secundum aliquid vera est. Est enim dupliciter aliquid per se notum; scilicet secundum se, et quoad nos. Deum igitur esse, secundum se est per se notum; non autem quoad nos; et ideo nobis necessarium est, ad hoc cognoscendum, demonstrationes habere ex effectibus sumptas. Et hoc quidem sic apparet.

11 See ibid: Ad hoc enim quod aliquid sit per se notum secundum se, nihil aliud requiritur nisi ut praedicatum sit de ratione subiecti; tunc enim subiectum cogitari non potest sine hoc quod praedicatum ei inesse appareat. Ad hoc autem quod sit per se notum nobis, oportet quod nobis sit cognita ratio subiecti in qua includitur praedicatum. Et inde est quod quaedam per se nota sunt omnibus; quando scilicet propositiones huiusmodi habent talia subiecta quorum ratio omnibus nota est, ut, omne totum maius est sua parte; quilibet enim scit quid est totum et quid est pars. Quaedam vero sunt per se nota sapientibus tantum, qui rationes terminorum cognoscunt, vulgo eas ignorante. For an excellent defense of Aquinas' on the necessity of demonstrating God's existence against the position Giles of Rome, see Gossiaux, Mark D. “Thomas Aquinas and Giles of Rome on the Existence of God as Self-Evident,” American Catholic Philosophical Quarterly 77 (2003): 57–79CrossRefGoogle Scholar.

12 See ibid: Et secundum hoc Boetius in Lib. de hebdomadibus dicit, quod duplex est modus communium conceptionum. Una est communis omnibus, ut, si ab aequalibus aequalia demas, et cetera. Alia quae est doctiorum tantum, ut puta incorporalia in loco non esse, quae non vulgus, sed docti comprobant; quia scilicet vulgi consideratio imaginationem transcendere non potest, ut ad rationem rei incorporalis pertingat.

13 See ibid: Hoc autem quod est esse, in nullius creaturae ratione includitur; cuiuslibet enim creaturae esse est aliud ab eius quidditate: unde non potest dici de aliqua creatura quod eam esse sit per se notum etiam secundum se. Sed in Deo esse ipsius includitur in suae quidditatis ratione, quia in eo est idem quod est et esse, ut Boetius dicit, et idem an est et quid est, ut dicit Avicenna; et ideo secundum se est per se notum. Sed quia quidditas Dei non est nobis nota, ideo quoad nos Deum esse non est nobis notum, sed indiget demonstratione.

14 SCG I, chap. 10: Illa enim per se esse nota dicuntur quae statim notis terminis cognoscuntur: sicut, cognito quid est totum et quid est pars, statim cognoscitur quod omne totum est maius sua parte. Huiusmodi autem est hoc quod dicimus Deum esse. Nam nomine Dei intelligimus aliquid quo maius cogitari non potest. Hoc autem in intellectu formatur ab eo qui audit et intelligit nomen Dei: ut sic saltem in intellectu iam Deum esse oporteat. Nec potest in intellectu solum esse: nam quod in intellectu et re est, maius est eo quod in solo intellectu est; Deo autem nihil esse maius ipsa nominis ratio demonstrat. Unde restat quod Deum esse per se notum est, quasi ex ipsa significatione nominis manifestum.

15 See ibid: Item. Cogitari quidem potest quod aliquid sit quod non possit cogitari non esse. Quod maius est evidenter eo quod potest cogitari non esse. Sic ergo Deo aliquid maius cogitari posset, si ipse posset cogitari non esse. Quod est contra rationem nominis. Relinquitur quod Deum esse per se notum est. Adhuc. Propositiones illas oportet esse notissimas in quibus idem de seipso praedicatur, ut, homo est homo; vel quarum praedicata in definitionibus subiectorum includuntur, ut, homo est animal. In Deo autem hoc prae aliis invenitur, ut infra ostendetur, quod suum esse est sua essentia, ac si idem sit quod respondetur ad quaestionem quid est, et ad quaestionem an est. Sic ergo cum dicitur, Deus est, praedicatum vel est idem subiecto, vel saltem in definitione subiecti includitur. Et ita Deum esse per se notum erit. Amplius. Quae naturaliter sunt nota, per se cognoscuntur: non enim ad ea cognoscenda inquisitionis studio pervenitur. At Deum esse naturaliter notum est: cum in Deum naturaliter desiderium hominis tendat sicut in ultimum finem, ut infra patebit. Est igitur per se notum Deum esse. Item. Illud per se notum oportet esse quo omnia alia cognoscuntur. Deus autem huiusmodi est. Sicut enim lux solis principium est omnis visibilis perceptionis, ita divina lux omnis intelligibilis cognitionis principium est: cum sit in quo primum maxime lumen intelligibile invenitur. Oportet igitur quod Deum esse per se notum sit.

16 SCG I, chap. 11: Nec oportet ut statim, cognita huius nominis Deus significatione, Deum esse sit notum, ut prima ratio intendebat. Primo quidem, quia non omnibus notum est, etiam concedentibus Deum esse, quod Deus sit id quo maius cogitari non possit: cum multi antiquorum mundum istum dixerint Deum esse. Nec etiam ex interpretationibus huius nominis Deus, quas Damascenus ponit, aliquid huiusmodi intelligi datur. Deinde quia, dato quod ab omnibus per hoc nomen Deus intelligatur aliquid quo maius cogitari non possit, non necesse erit aliquid esse quo maius cogitari non potest in rerum natura. Eodem enim modo necesse est poni rem, et nominis rationem. Ex hoc autem quod mente concipitur quod profertur hoc nomine Deus, non sequitur Deum esse nisi in intellectu. Unde nec oportebit id quo maius cogitari non potest esse nisi in intellectu. Et ex hoc non sequitur quod sit aliquid in rerum natura quo maius cogitari non possit. Et sic nihil inconveniens accidit ponentibus Deum non esse: non enim inconveniens est quolibet dato vel in re vel in intellectu aliquid maius cogitari posse, nisi ei qui concedit esse aliquid quo maius cogitari non possit in rerum natura.

17 See ibid: Nec etiam oportet, ut secunda ratio proponebat, Deo posse aliquid maius cogitari si potest cogitari non esse. Nam quod possit cogitari non esse, non ex imperfectione sui esse est vel incertitudine, cum suum esse sit secundum se manifestissimum: sed ex debilitate nostri intellectus, qui eum intueri non potest per seipsum, sed ex effectibus eius, et sic ad cognoscendum ipsum esse ratiocinando perducitur.

18 See ibid: Ex quo etiam tertia ratio solvitur. Nam sicut nobis per se notum est quod totum sua parte sit maius, sic videntibus ipsam divinam essentiam per se notissimum est Deum esse, ex hoc quod sua essentia est suum esse. Sed quia eius essentiam videre non possumus, ad eius esse cognoscendum non per seipsum, sed per eius effectus pervenimus.Ad quartam etiam patet solutio. Sic enim homo naturaliter Deum cognoscit sicut naturaliter ipsum desiderat. Desiderat autem ipsum homo naturaliter inquantum desiderat naturaliter beatitudinem, quae est quaedam similitudo divinae bonitatis. Sic igitur non oportet quod Deus ipse in se consideratus sit naturaliter notus homini, sed similitudo ipsius. Unde oportet quod per eius similitudines in effectibus repertas in cognitionem ipsius homo ratiocinando perveniat.

19 See ibid: Ad quintam etiam de facili patet solutio. Nam Deus est quidem quo omnia cognoscuntur, non ita quod alia non cognoscantur nisi eo cognito, sicut in principiis per se notis accidit: sed quia per eius influentiam omnis causatur in nobis cognitio; Cf. Super Boethium De Trinitate, q. 1, a. 1; trans. Rose E. Brennan, S.H.N. (Herder, 1946), and Scriptum Super Libros Sententiarum, I, d. III, q. 1, a. 1; trans. Peter Kwasnieski: http://www4.desales.edu/∼philtheo/loughlin/ATP/index.html, November 4, 2011; See Elders, Leo The Philosophical Theology of St. Thomas Aquinas (Leiden, New York: E.J. Brill, 1990), 61CrossRefGoogle Scholar.

20 St. Thomas Aquinas, The Summa Theologiae Prima Pars, trans. Alfred Freddoso: http://www.nd.edu/∼afreddos/summa-translation/TOC-part1.htm, q. 2, a. 1, Respondeo: dicendum quod contingit aliquid esse per se notum dupliciter, uno modo, secundum se et non quoad nos; alio modo, secundum se et quoad nos. Ex hoc enim aliqua propositio est per se nota, quod praedicatum includitur in ratione subiecti, ut homo est animal, nam animal est de ratione hominis. Si igitur notum sit omnibus de praedicato et de subiecto quid sit, propositio illa erit omnibus per se nota, sicut patet in primis demonstrationum principiis, quorum termini sunt quaedam communia quae nullus ignorat, ut ens et non ens, totum et pars, et similia. Si autem apud aliquos notum non sit de praedicato et subiecto quid sit, propositio quidem quantum in se est, erit per se nota, non tamen apud illos qui praedicatum et subiectum propositionis ignorant. Et ideo contingit, ut dicit Boetius in libro de hebdomadibus, quod quaedam sunt communes animi conceptiones et per se notae, apud sapientes tantum, ut incorporalia in loco non esse. Dico ergo quod haec propositio, Deus est, quantum in se est, per se nota est, quia praedicatum est idem cum subiecto; Deus enim est suum esse, ut infra patebit. Sed quia nos non scimus de Deo quid est, non est nobis per se nota, sed indiget demonstrari per ea quae sunt magis nota quoad nos, et minus nota quoad naturam, scilicet per effectus.

21 See ibid., q. 2, a.1, ad. 1 and 2: Ad primum ergo dicendum quod cognoscere Deum esse in aliquo communi, sub quadam confusione, est nobis naturaliter insertum, inquantum scilicet Deus est hominis beatitudo, homo enim naturaliter desiderat beatitudinem, et quod naturaliter desideratur ab homine, naturaliter cognoscitur ab eodem. Sed hoc non est simpliciter cognoscere Deum esse; sicut cognoscere venientem, non est cognoscere Petrum, quamvis sit Petrus veniens, multi enim perfectum hominis bonum, quod est beatitudo, existimant divitias; quidam vero voluptates; quidam autem aliquid aliud. Ad secundum dicendum quod forte ille qui audit hoc nomen Deus, non intelligit significari aliquid quo maius cogitari non possit, cum quidam crediderint Deum esse corpus. Dato etiam quod quilibet intelligat hoc nomine Deus significari hoc quod dicitur, scilicet illud quo maius cogitari non potest; non tamen propter hoc sequitur quod intelligat id quod significatur per nomen, esse in rerum natura; sed in apprehensione intellectus tantum. Nec potest argui quod sit in re, nisi daretur quod sit in re aliquid quo maius cogitari non potest, quod non est datum a ponentibus Deum non esse.

22 Christopher J. Martin, Thomas Aquinas: God and Explanations (Edinburgh: Edinburgh University Press, 1997) 82; also see Martin's Ch. 7 on “Whether the Existence of God is a Scientific Question.”

23 See In I Post. Anal., lect 4.

24 Martin, God and Explanations, 87.

25 ST I, q. 2, a. 2, ad. 2: Ad secundum dicendum quod cum demonstratur causa per effectum, necesse est uti effectu loco definitionis causae, ad probandum causam esse, et hoc maxime contingit in Deo. Quia ad probandum aliquid esse, necesse est accipere pro medio quid significet nomen non autem quod quid est, quia quaestio quid est, sequitur ad quaestionem an est. Nomina autem Dei imponuntur ab effectibus, ut postea ostendetur, unde, demonstrando Deum esse per effectum, accipere possumus pro medio quid significet hoc nomen Deus.

26 See ibid., q. 3, a. 4, obj. 2: Praeterea, de Deo scire possumus an sit, ut supra dictum est. Non autem possumus scire quid sit. Ergo non est idem esse Dei, et quod quid est eius, sive quidditas vel natura

27 See ibid., ad. 2: Ad secundum dicendum quod esse dupliciter dicitur, uno modo, significat actum essendi; alio modo, significat compositionem propositionis, quam anima adinvenit coniungens praedicatum subiecto. Primo igitur modo accipiendo esse, non possumus scire esse Dei, sicut nec eius essentiam, sed solum secundo modo. Scimus enim quod haec propositio quam formamus de Deo, cum dicimus Deus est, vera est. Et hoc scimus ex eius effectibus, ut supra dictum est.

28 See McInerny, Lecture Seven entitled “Intemperate Reasoning,” 83–94. Responding to why a demonstration, if successful, does not lead one to “believe in God,” McInerny distinguishes between the theoretical and practical intellect. Demonstrations are concerned with growth in knowledge concerning that which was previously unknown to that which is known. Demonstrations are in regards to the theoretical intellect, whose finis is the perfection of the mind. The practical intellect only refers to the perfection of things to be done or made. While the theoretical and practical intellects form one intellect, they nevertheless have distinct objects which characterize their perfection. For a criticism of the project of natural theology regarding this point, see Smith, John, “Prospects for Natural Theology,” The Monist 75 (1992): 406–420CrossRefGoogle Scholar.

29 “The Reformed Objection to Natural Theology,” American Catholic Philosophical Quarterly 54 (1980)Google Scholar.

30 Plantinga, “Reformed Objection,” 49.

31 In another work, “Reason and Belief in God” (1983), Plantinga includes Karl Barth as a third Reformed thinker who opposes natural theology. I do not treat of Barth in this essay, since Plantinga's analysis of Barth's position is the shortest and least substantial of the three. For critiques of Barth's objections to natural theology, see Barr, James Biblical Faith and Natural Theology: Gifford Lectures for 1991 Delivered at the University of Edinburgh. (Oxford: Clarendon Press, 1993)Google Scholar and Davies, Brian, “Theology and Natural Theology,” New Blackfriars 58 (June, 1977): 256–267CrossRefGoogle Scholar.

32 Plantinga, “Reformed Objection,” 49.

33 Ibid.

34 Ibid., 50.

35 Ibid.

36 Ibid.

37 Kretzmann, Norman, The Metaphysics of Theism: Aquinas' Natural Theology in Summa Contra Gentiles I (Oxford: Clarendon Press, 1997), 12Google Scholar. Kretzmann has not only provided extended and substantial critiques of Plantinga's position, but has done so in a way that is far superior to the attempts in this paper.

38 Kretzmann, Metaphysics of Theism, 13.

39 Ibid., 14; this passage is taken from Plantinga's essay, “Reason and Belief,” (1983).

40 Plantinga, “Reformed Objection,” 50.

41 See James Barr, Biblical Faith and Natural Theology.

42 Plantinga, “Reformed Objection,” 51.

43 Kretzmann, Metaphysics of Theism, 17.

44 Plantinga, “Reformed Objection,” 51

45 Ibid.

46 Ibid., 52.

47 Kretzmann, Metaphysics of Theism, 18.

48 Plantinga, “Reformed Objection,” 53.

49 For an illuminating discussion of this topic, see McInerny, Ralph, Preambula Fidei: Thomism and the God of the Philosophers (Washinton, D.C.: CUA Press, 2006), 6–32Google Scholar.

50 See De Veritate, q. 14, a. 1, Respondeo: Sic igitur intellectus noster possibilis respectu partium contradictionis se habet diversimode. Quandoque enim non inclinatur ad unum magis quam ad aliud, vel propter defectum moventium, sicut in illis problematibus de quibus rationes non habemus; vel propter apparentem aequalitatem eorum quae movent ad utramque partem. Et ista est dubitantis dispositio, qui fluctuat inter duas partes contradictionis. Quandoque vero intellectus inclinatur magis ad unum quam ad alterum; sed tamen illud inclinans non sufficienter movet intellectum ad hoc quod determinet ipsum in unam partium totaliter; unde accipit quidem unam partem, semper tamen dubitat de opposita. Et haec est dispositio opinantis, qui accipit unam partem contradictionis cum formidine alterius. Quandoque vero intellectus possibilis determinatur ad hoc quod totaliter adhaereat uni parti; sed hoc est quandoque ab intelligibili, quandoque a voluntate. Ab intelligibili quidem quandoque quidem mediate, quandoque autem immediate. Immediate quidem quando ex ipsis intelligibilibus statim veritas propositionum intellectui infallibiliter apparet. Et haec est dispositio intelligentis principia, quae statim cognoscuntur notis terminis, ut philosophus dicit. Et sic ex ipso quod quid est, immediate intellectus determinatur ad huiusmodi propositiones. Mediate vero, quando cognitis definitionibus terminorum, intellectus determinatur ad alteram partem contradictionis, virtute primorum principiorum. Et ista est dispositio scientis. Quandoque vero intellectus non potest determinari ad alteram partem contradictionis neque statim per ipsas definitiones terminorum, sicut in principiis, nec etiam virtute principiorum, sicut est in conclusionibus demonstrationis; determinatur autem per voluntatem, quae eligit assentire uni parti determinate et praecise propter aliquid, quod est sufficiens ad movendum voluntatem, non autem ad movendum intellectum, utpote quia videtur bonum vel conveniens huic parti assentire. Et ista est dispositio credentis, ut cum aliquis credit dictis alicuius hominis, quia videtur ei decens vel utile. Et sic etiam movemur ad credendum dictis Dei, inquantum nobis repromittitur, si crediderimus, praemium aeternae vitae: et hoc praemio movetur voluntas ad assentiendum his quae dicuntur, quamvis intellectus non moveatur per aliquid intellectum.

51 De Veritate, q. 14, a. 2, Respondeo: fides est habitus mentis, qua inchoatur vita aeterna in nobis, faciens intellectum non apparentibus assentire. This is important in light of Plantinga's understanding of belief, which becomes reduced to “mere willing.” Equivocating belief with “mere willing” is an unfortunate inclination in Protestant theology. I would like to thank Daniel Wagner for his helpful insights regarding this notion of belief. For an excellent analysis of this point, see Swineburne, Richard, “Natural Theology, Its Dwindling Probablities, and Lack of Rapport,” Faith and Philosophy 21 (2004): 533–46CrossRefGoogle Scholar.

52 See De Veritate, q. 14, a. 9, Sed contra: Unde fidei obiectum proprie est id quod est absens ab intellectu. Creduntur enim absentia, sed videntur praesentia, ut in eodem Lib. Augustinus dicit, vel etiam res non apparens, id est res non visa: quia, ut dicitur Hebr., XI, 1, fides est argumentum non apparentium. Quandocumque autem deficit ratio proprii obiecti, oportet quod et actus deficiat; unde, quam cito incipit aliquid esse praesens vel apparens, non potest ut obiectum subesse actui fidei.

53 See ibid:Quaecumque autem sciuntur, proprie accepta scientia, cognoscuntur per resolutionem in prima principia, quae per se praesto sunt intellectui; et sic omnis scientia in visione rei praesentis perficitur. Unde impossibile est quod de eodem sit fides et scientia.

54 Gornall, Thomas, A Philosophy of God: The Elements of Thomistic Natural Theology (New York: Sheed and Ward, 1959), 35Google Scholar.