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CHAPTER 1

How Do I Know Christianity Is True?

Before we attempt to build a case for Christianity, we must come to grips with some very fundamental questions about the nature and relationship of faith and reason. Exactly how do we know Christianity to be true? Is it simply by a leap of faith or on the authority of the Word of God, both unrelated to reason? Does religious experience assure us of the truth of the Christian faith, so that no further justification is needed? Or is an evidential foundation for faith necessary, without which faith would be unjustified and irrational? We can better answer these questions if we briefly survey some of the most important representative thinkers of the past.

Historical Background

Medieval

In our historical survey, let's look first at Augustine (354–430) and Thomas Aquinas (1224–1274). Their approaches were determinative for the Middle Ages.

AUGUSTINE

Augustine's attitude toward faith and reason is very difficult to interpret, especially because his views apparently evolved over the years. Sometimes we get the impression that he was a strict authoritarian; that is to say, he held that the ground for faith was sheer, unquestionable, divine authority. This authority might be expressed in either the Scriptures or in the church. Thus, Augustine confessed, "I should not believe the Gospel except as moved by the authority of the Catholic Church." The authority of Scripture he held in even higher esteem than that of the church. Because the Scriptures are inspired by God, they are completely free from error and are therefore to be believed absolutely. Such a view of authority would seem to imply that reason has no role to play in the justification of belief, and sometimes Augustine gives that impression. He asserts that one must first believe before he can know. He was fond of quoting Isaiah 7:9 in the Septuagint version: "Unless you believe you shall not understand." The fundamental principle of the Augustinian tradition throughout the Middle Ages was fides quaerens intel-lectum: faith seeking understanding.

But certain statements of Augustine's make it clear that he was not an unqualified authoritarian. He maintained that authority and reason cooperate in bringing a person to faith. Authority demands belief and prepares man for reason, and reason in turn leads to understanding and knowledge. But at the same time, reason is not entirely absent from authority, for one has to consider whom to believe, and the highest authority belongs to clearly known truth; that is to say, the truth, when it is clearly known, has the highest claim to authority because it demands our assent. According to Augustine, it is our duty to consider what men or what books we ought to believe in order to worship God rightly. Gerhard Strauss, in his book on Augustine's doctrine of Scripture, explains that although for Augustine Scripture is absolutely authoritative and inerrant in itself, it does not carry credibility in itself — that is, people will not automatically accept its authority upon hearing it. Therefore, there must be certain signs (indicia) of credibility that make its authority evident. On the basis of these signs, we can believe that the Scripture is the authoritative Word of God and submit to its authority. The principal signs adduced by Augustine on behalf of the authority of Scripture are miracle and prophecy. Though many religions boast of revelations showing the way of salvation, only the Scriptures have the support of miracle and prophecy, which prove it to be the true authority.

Thus, Augustine's authoritarianism would seem to be drastically qualified. Perhaps Augustine's apparent inconsistency is best explained by the medieval understanding of authority. In the early church, authority (auctoritas) included not just theological truths but the whole tradition of past knowledge. The relationship between authority and reason was not the same as that between faith and reason. Rather it was the relationship between all past knowledge and present-day understanding. Knowledge of the past was simply accepted on the basis of authority. This seems to have been Augustine's attitude. He distinguishes between what is seen to be true and what is believed to be true. We see that something is true by either physical perception or rational demonstration. We believe that something is true on the basis of the testimony of others. Hence, with regard to miracle and prophecy, Augustine says that the trustworthiness of reports of either past or future events must be believed, not known by the intelligence. Elsewhere he declares that one should believe in God because belief in him is taught in the books of men who have left their testimony in writing that they lived with the Son of God and saw things that could not have happened if there were no God. Then he concludes that one must believe before he can know. Since for Augustine the historical evidence for miracle and prophecy lay in the past, it was in the realm of authority, not reason. Today, on the other hand, we would say that such a procedure would be an attempt to provide a rational foundation for authority via historical apologetics.

Now the obvious question at this point is, Why accept the authority of the writers of the past, whether they be the classical writers or the authors of Scripture? Clearly, if Augustine is to avoid circular reasoning, he cannot say that we should accept the authority of the evangelists because of the authority of Scripture, for it is the evangelists' testimony to miracle and prophecy that is supposed to make evident the authority of Scripture. So Augustine must either come up with some reason to accept the evangelists' testimony as reliable or abandon this historically oriented approach. Since he lacked the historical method, the first alternative was not open to him. Therefore, he chose the second. He frankly admits that the books containing the story of Christ belong to an ancient history that anyone may refuse to believe. Therefore, he turns to the present miracle of the church as the basis for accepting the authority of Scripture. He saw the very existence of the mighty and universal church as an overwhelming sign that the Scriptures are true and divine.

Now notice that Augustine is not basing the authority of Scripture on the authority of the church, for he held the Scripture's authority to exceed even that of the church. Rather, his appeal is still to the sign of miracle, not indeed the Gospel miracles, which are irretrievably removed in the past, but the present and evident miracle of the church. In The City of God he states that even if the unbeliever rejects all biblical miracles, he is still left with one stupendous miracle, which is all one needs, namely, the fact of the whole world believing in Christianity without the benefit of the Gospel miracles. It's interesting that, by appealing to a present miracle as the sign of the authority of Scripture, Augustine seems to have implicitly denied authoritarianism, since this sign was not in the past, in the realm of authority where it could only be believed, but in the present, where it could be seen and known. Be that as it may, Augustine's emphases on biblical authority and signs of credibility were to set the tone for subsequent medieval theology.

THOMAS AQUINAS

Aquinas's Summa contra gentiles, written to combat Greco-Arabic philosophy, is the greatest apologetic work of the Middle Ages and so merits our attention. Thomas develops a framework for the relationship of faith and reason that includes the Augustinian signs of credibility. He begins by making a distinction within truths about God. On the one hand, there are truths that completely surpass the capability of human reason, for example, the doctrine of the Trinity. On the other hand, many truths lie within the grasp of human reason, such as the existence of God. In the first three volumes of the Summa contra gentiles, Thomas attempts to prove these truths of reason, including the existence and nature of God, the orders of creation, the nature and end of man, and so forth. But when he comes to the fourth volume, in which he handles subjects like the Trinity, the incarnation, the sacraments, and the last things, he suddenly changes his method of approach. He states that these things are to be proved by the authority of Holy Scripture, not by natural reason. Because these doctrines surpass reason, they are properly objects of faith.

Now at first blush this seems to suggest that for Aquinas these truths of faith are mysteries, somehow "above logic." But here we must be very careful. For as I read Aquinas, that's not how he defines his terms. Rather he seems to mean that truths of faith surpass reason in the sense that they are neither empirically evident nor demonstrable with absolute certainty. He makes no suggestion that truths of faith transcend Aristotelian logic. Rather there are just no empirical facts which make these truths evident or from which these truths may be inferred. For example, although the existence of God can be proved from his effects, there are no empirical facts from which the Trinity may be inferred. Or again, the eschatological resurrection of the dead cannot be proved, because there is no empirical evidence for this future event. Elsewhere Thomas makes it clear that truths of faith cannot be demonstrated by reason alone, either. He maintains that we Christians must use only arguments that prove their conclusions with absolute certainty; for if we use mere probability arguments, the insufficiency of those arguments will only serve to confirm the non-Christian in his unbelief.

Thus, the distinction Thomas makes between truths of reason and truths of faith is rather like Augustine's distinction between seeing and believing. Truths of reason may be "seen" — that is, either proved with rational certainty or accepted as empirically evident — whereas truths of faith must be believed, since they are neither empirically evident nor rationally provable. This does not mean that truths of faith are incomprehensible or "above logic."

Now because truths of faith can only be believed, does this imply that Thomas is in the end a fideist or an authoritarian? The answer seems clearly no. For like Augustine he proceeds to argue that God provides the signs of miracle and prophecy, which serve to confirm the truths of faith, though not demonstrating them directly. Because of these signs, Aquinas held that a man can see the truths of faith: "Then they are indeed seen by the one who believes; he would not believe unless he saw that they are worthy of belief on the basis of evident signs or something of this sort." Thomas calls these signs "confirmations," "arguments," and "proofs" for the truths of faith. This seems to make it clear that Aquinas believed there are good grounds for accepting the truths of faith as a whole. The proofs of miracle and prophecy are compelling, although they are indirect. Thus, for example, the doctrine of the Trinity is a truth of faith because it cannot be directly proved by any argument; nevertheless, it is indirectly proved insofar as the truths of faith taken together as a whole are shown to be credible by the divine signs.

Thomas's procedure, then, may be summarized in three steps: (1) Fulfilled prophecies and miracles make it credible that the Scriptures taken together as a whole are a revelation from God. (2) As a revelation from God, Scripture is absolutely authoritative. (3) Therefore, those doctrines taught by Scripture that are neither demonstrably provable nor empirically evident may be accepted by faith on the authority of Scripture. Thus, Aquinas can say that an opponent may be convinced of the truths of faith on the basis of the authority of Scripture as confirmed by God with miracles.

Again the question arises: How do we know that the purported miracles or fulfilled prophecies ever took place? The medieval thinkers, lacking the historical method, could not answer this question. They developed a philosophical framework in which the signs of credibility confirmed the truths of faith, but they had no way of proving the signs themselves. About the only argument was Augustine's indirect proof from the miracle of the church. Thus, Thomas declares,

Now such a wondrous conversion of the world to the Christian faith is a most indubitable proof that such signs did take place. ... For it would be the most wondrous sign of all if without any wondrous signs the world were persuaded by simple and lowly men to believe things so arduous, to accomplish things so difficult, and to hope for things so sublime.

A final word might be added. With Aquinas we see the reduction of faith to an epistemological category; that is to say, faith was no longer trust or commitment of the heart, but became a way of knowing, complementary to reason. Faith was essentially intellectual assent to doctrines not provable by reason — hence, Aquinas's view that a doctrine cannot be both known and believed: if you know it (by reason), then you cannot believe it (by faith). Thus, Aquinas diminished the view of faith as trust or commitment. This same intellectualist understanding of faith characterized the documents of the Council of Trent and of Vatican I but was adjusted in the documents of Vatican II.

The Enlightenment

The fact that the Enlightenment is also known as the Age of Reason gives us a good clue as to how thinkers of that period regarded the relationship between faith and reason. Nevertheless, there was not complete agreement on this issue, and the two figures we shall survey represent two fundamentally opposed viewpoints.

JOHN LOCKE

The thought of John Locke (1632–1704) was determinative for the eighteenth century. His Essay Concerning Human Understanding (1689) laid down the epistemological principles that were to shape religious thought during that age. Though he rejected the philosophical rationalism of Descartes, Locke was nevertheless an ardent theological rationalist. That is to say, he maintained that religious belief must have an evidential foundation and that where such a foundation is absent, religious belief is unwarranted. Locke himself attempted to provide such an evidential foundation.

Locke argued for the existence of God by means of a cosmological argument — indeed, he maintained that the existence of God is "the most obvious truth that reason discovers," having an evidence "equal to mathematical certainty." When one moves beyond such matters of demonstrable reason into matters of faith, Locke insisted that revealed truths cannot contradict reason. God can reveal to us both truths attainable by reason (though reason gives greater certainty of these than does revelation) as well as truths unattainable by reason. The revealed truths unattainable by reason cannot contradict reason, because we shall always be more certain of the truth of reason than we shall be of a purported revelation that contradicts reason. Therefore, no proposition contrary to reason can be accepted as divine revelation. Thus, although we know that a revelation from God must be true, it still lies within the scope of reason to determine if a supposed revelation really is from God and to determine its meaning.

More than that, revelation must not only be in harmony with reason but must itself be guaranteed by appropriate rational proofs that it is indeed divine. Otherwise, one degenerates into irresponsible enthusiasm: Revelation is natural reason enlarged by a new set of discoveries communicated by God immediately, which reason vouches the truth of by the testimony and proofs it gives that they come from God. So that he that takes away reason to make way for revelation, puts out the light of both; and does much the same as if he would persuade a man to put out his eyes, the better to receive the remote light of an invisible star by a telescope..

Religious enthusiasm was the form of religious expression most scorned by the intellectualist believers of the Age of Reason, and Locke would have nothing to do with it. Only if reason makes plausible that a purported revelation is genuine can that revelation be believed.

Hence, in his subsequent works The Reasonableness of Christianity (1695) and Discourse on Miracles (1690), Locke argued that fulfilled prophecy and palpable miracles furnish proof of Christ's divine mission. He set forth three criteria for discerning a genuine revelation. First, it must not be dishonoring to God or inconsistent with natural religion and the natural moral law. Second, it must not inform man of things indifferent, insignificant, or easily discovered by natural ability. Third, it must be confirmed by supernatural signs. For Locke, the chief of these signs was miracle. On the basis of Jesus' miracles, we are justified in regarding him as the Messiah and his revelation from God as true.

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Excerpted from "Reasonable Faith"
by .
Copyright © 2008 William Lane Craig.
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