by Steven B. Cowan –

This is the apologetics question. Every other question that someone might ask regarding the defense of the faith is related in some way to this bottom-line query: How do we know that Christianity is true?

Elsewhere in this issue, James Beilby and David Clark have outlined for us a general epistemology, explaining how human beings acquire and justify knowledge. J.P. Moreland has also demolished certain obstacles that are thrown up by unbelievers to block the path to religious knowledge. My task in this article, building on the work of these and other scholars, is to take us down that path to religious knowledge and explain just how it is that we may be warranted in claiming that the Christian faith is true.

Let me be clear, however, that this article is not intended to provide a thorough and comprehensive apologetic for the faith. I will only be explaining, as a matter of epistemological theory, how we may legitimately claim to know that Christianity is true. Speaking metaphorically, I will lay out the correct route one must take on the path of religious knowledge to arrive at establishing (or justifiably believing) the truth of Christianity.

Knowing Vs. Showing

When someone asks, “How do you know that Christianity is true?”, they might mean one of two things by this question. They might be asking whether or not we know that Christianity is true and by what means we know this. Or, they might be asking for us to prove that we know that Christianity is true. Though these two questions may certainly overlap, they are not the same question. The first question asks for an explanation, the second question asks for an argument.

In light of these two different ways of understanding the question of how we know that Christianity is true, we may make a further distinction. Following the lead of Christian philosopher William Lane Craig, I will distinguish between knowing that Christianity is true and showing that Christianity is true.1 Now it could very well be the case that I know that Christianity is true in virtue of being able to show that Christianity is true by means of some elaborate philosophical and/or historical arguments. However, it could also be the case that I know that Christianity is true quite apart from being able to show that it is true. That is, my knowing that Christianity is true may not be directly based on having shown that it is true. This is what William Lane Craig has argued, and I believe that he is right. I will elaborate below.

Knowing that Christianity Is True

I believe that every true, born-again Christian knows that Christianity is true. He knows that God exists. He knows that Jesus is God in the flesh, that he died on the cross for our sins and rose again the third day. He knows the Holy Bible is the Word of God. He knows that he has been saved by God’s grace and adopted into his family. How does the Christian know all of this? Does he know it because he has searched out all the scientific and historical evidence for the truth of the Christian faith? Does he know it because he has studied and refuted all the objections to Christianity raised by the skeptics? Probably not. Very few Christians are professional apologists. Yet, if one’s knowing that Christianity is true were based on one’s having proved it by means of detailed apologetic arguments, then very few Christians could claim to know that Christianity is true. But, I have said that every Christian knows the truth of his faith. So, it can’t (always) be by means of having proved it.

Well, how does the Christian know his faith is true? He knows it because of the presence of the Holy Spirit who lives in his heart and who “bears witness with our spirit that we are children of God” (Rom. 8:17). The Christian knows that Christianity is true because the Holy Spirit provides what theologians call the “internal testimony of the Holy Spirit.” Many other biblical passages speak of this internal testimony. For example, in 1 Thessalonians 1:5, Paul reminds the new believers in that church that his “gospel did not come to you in word only, but also in power and in the Holy Spirit and with full conviction.” Likewise, John speaks of the inner witness of the Spirit, noting its superiority to the historical testimony regarding the ministry of Jesus: “And it is the Spirit who testifies, because the Spirit is the truth. . . . We accept man’s testimony, but God’s testimony is greater because it is the testimony of God, which he has given about his Son. Anyone who believes in the Son of God has this testimony” (1 John 5:6-10). As William Lane Craig explains,

I think it is evident that Paul and John are not talking about an argument from religious experience for the conclusion that Christianity is true, but about an immediate apprehension of its truth acquired in the context of the Spirit’s witness. Belief that one’s Christian faith is true is what epistemologists call a “properly basic” belief—that is, a belief which is not derived inferentially from any more foundational belief but which is rationally justified by being formed in appropriate circumstances. Belief in the Christian God is properly basic when formed in the circumstances of the witness of the Holy Spirit.2

A person who has the internal witness of the Holy Spirit not only justifiably believes in the truth of Christianity, but he knows that his faith is true. As I write this article, I can see outside the window of my office a very tall pine tree. Because of this experience of seeing a pine tree, I naturally and immediately form the belief, “There is a tall pine tree outside my window.” I do not come to believe this as the result of some reasoning process. I do not have an argument that leads me to this belief. Yet my belief is surely justified. My belief that there is a pine tree outside my window is a properly basic belief. More than that, since my visual sense is generally trustworthy and I have no good reason to doubt its reliability right now, I can rightly claim to know that there is a pine tree outside my window. Likewise, because the Holy Spirit testifies to my heart of the truth of Christianity, I can rightly claim to know that Christianity is true.3

Showing that Christianity Is True

We know that Christianity is true because of the internal testimony of the Holy Spirit. So, we have answered the first way of understanding the question, “How do you know that Christianity is true?” which seeks an explanation for how it is the case that we know this. However, Christianity can also be shown to be true. That is, we can offer arguments and point to objective scientific and historical evidences which rationally justify belief in the Christian faith. And what is more, I think we can show the truth of Christianity in such a way that it is not only reasonable for a person to believe in Christianity, but that Christianity ought to be believed by any rational person, and that other religions ought to be rejected. So, we can also provide an answer to the second way of understanding the question, “How do you know Christianity is true?” which seeks not an explanation for the existence of our knowledge, but seeks a proof that what we claim to know is in fact true. The proof for Christianity has four aspects which I will outline below.

Christianity is Shown in Part by the Fact that All Other Worldviews Are Incoherent

A worldview is a conceptual framework by which a person organizes and interprets his experience. Worldviews consist of certain fundamental beliefs about key concepts such as God, reality, knowledge, and ethics.4 Basically, there are three worldviews: (1) Theism, the Judeo-Christian view that the physical universe and human beings are the creation of a supremely good and powerful God who exists eternally and unchangeably, and who rules providentially over his creation; (2) Pantheism, the (usually) Eastern view that all that ultimately exists is God, and that the universe is merely an illusion or a manifestation of God; (3) Naturalism, the view that the physical universe is all that exists, that there is no God or supernatural realm of any kind.

Since these are the only viable options for worldviews, then theism may be established by a process of elimination. For naturalism and pantheism are incoherent. That is, they are logically contradictory in such a way as to render them false.

As Alvin Plantinga has shown, naturalism is logically contradictory because on naturalistic assumptions one would have no reason to believe that naturalism is true.5 Consider the fact that naturalism teaches that the universe is simply a cosmic accident, and that human beings arose through blind and purposeless evolutionary forces. On this view, all of our faculties—our arms and legs, our walking upright, our moral systems, and our every belief—exist for no other reason than that they help us to survive in some way. In other words, belief-forming faculties do not exist (as we might have thought) in order to tell us the truth about the world, but simply to help us survive. Our minds adopt beliefs for their survival value, not for their truth value. Now if all our beliefs arise because they help us survive rather than aim at the truth, then the naturalist believes in naturalism not because it is true but because it provides him with some survival benefit.

And it is easy to see that false beliefs may help us survive in a hostile environment just as surely as true beliefs would. Suppose I live in a jungle populated by deadly creatures who desire to eat me. In order to survive, I must avoid these creatures. And suppose one day I see a man-eating tiger coming toward me, and I run away to safety. I survived the danger because I believed that there was a tiger coming toward me and I believed that by running in a certain direction I could escape. However, suppose that it wasn’t really a tiger that was coming after me. Suppose it was one of J.R.R. Tolkien’s Balrogs instead, and that my (faulty) sensory faculties falsely informed me that it was a tiger. Nevertheless, my false belief enabled me to survive just as well. So, since false beliefs have survival value just as well as true beliefs, and the naturalist comes to believe in naturalism solely for its survival benefit, it follows that the naturalist has no reason to believe that naturalism is true. His worldview is thus incoherent.

Similar problems plague the pantheist. As Paul Copan points out, the pantheist will deny the laws of logic; he will argue that logical principles touted in so-called “Western” logic such as the Law of Non-contradiction6 do not apply to reality. Yet, paradoxically, such a denial violates the pantheist belief that distinctions between different things are illusory. Copan explains: “The Easterner is assuming that he must decide between either Western logic or Eastern logic. If making distinctions is not necessary to discern truth, then the [pantheist] cannot hope to explain his view.”7 So, pantheism is also incoherent.

It would seem, then, that theism wins the day (assuming that theism is coherent). This does not mean that we have directly proven that theism is true, but it does mean that the only acceptable worldview is theism.

Christianity is Shown in Part by the Fact that Theism is Philosophically Demonstrable

We can move beyond the mere rational acceptability of Theism, however, to provide positive arguments in its favor. Historically, there have been several arguments for God’s existence and most of them still find defenders today. Many of these arguments have merit, but for brevity’s sake I will discuss only two.

One very powerful argument for God’s existence is the Kalam Cosmological Argument which has been ably defended in recent days by William Lane Craig.8 The argument proceeds in three stages, successively showing that (1) the universe had a beginning, (2) the beginning of the universe was caused, and (3) the cause of the universe was God.

Stage one, the thesis that the universe had a beginning, may be defended in a number of ways both philosophically and scientifically. For example, if we accept the Big Bang Theory that the universe began some time ago from a great explosion “out of nothing,” then we must accept that the universe had a beginning. Most importantly, however, we may show that the idea of a beginning-less, eternal universe is logically impossible. For if the universe has always existed, then the number of past events has been infinite. That means that prior to the present moment an infinite number of past events have been traversed, that is, have successively occurred.

But here’s the problem: an infinite number of events cannot be traversed. To complete an infinite number of past events would be like trying to count all the whole numbers. It simply cannot be done. In fact, it cannot be done by definition. A series of past events which could be successively traversed would be a finite series. So, it is impossible to traverse an infinite past to get to the present moment. But, the present moment exists. Therefore, the past must be finite, and the universe must have had a beginning.

Stage two is a bit easier to defend. It says that the universe had a cause. Why? Because the universe had a beginning. One of the most certain things we know is that whatever begins to exist has a cause. It is impossible (and no one seriously believes) that something can literally come from nothing. So, the universe, which began to be a finite time ago, had a cause.

What was the cause of the universe? Stage three asserts that God was the cause. William Lane Craig defends this stage of the argument by pointing out that the cause of the universe must have certain attributes very much like God’s. Only an eternal, immutable, spiritual Person is adequate to explain the universe’s coming to be out of nothing.9

Another powerful argument for God’s existence is the Moral Argument. This argument begins by showing that if God does not exist, then there can be no objective moral values. As Dostoyevsky, the famous Russian novelist, said in The Brothers Karamozov, “If there is no God, then everything is permitted.” Both naturalism and pantheism logically entail moral relativism. If, as the naturalist insists, we are nothing but cosmic accidents, thrown into the world by nothing and for no purpose, then there can be no basis for the sanctity of human life. And without the sanctity of human life, there can be no objective basis for the ethical treatment of human beings. Human life is no more valuable than cockroach life, or, for that matter, than non-life. Pantheism teaches that moral concepts like “good” and “bad” are part of the illusion of the physical world. All that exists is one thing—God. Any distinction between this and that, between this and not-this, is unreal. So, the distinction between good and bad are unreal. This means that morality is relative because on this view there is no difference between taking life and saving life, between helping and hurting, between Mother Theresa and Adolf Hitler. So, if God does not exist, then there are no objective moral values.

However, it is clear that there are objective moral values. I know, for instance, that torturing children for the fun of it is wrong. And so does everyone else. Even the naturalist and the pantheist know that such things are wrong. When the atheist Bertrand Russell advocates for nuclear disarmament, he acknowledges that there are objective moral principles. When the Hindu pantheist insists that he must do “good” deeds to work off his “bad” karma, he clearly (and inconsistently) admits that some things really are right and wrong. Yet, these worldviews cannot account for the existence of such objective moral values. As we have seen, there can be objective morality only if God exists. Therefore, God must exist.10

Christianity is Shown in Part by the Fact that Historical Evidence Supports the Christian Claims about Jesus

Establishing that theism is the correct worldview only gets us so far. Jews and Muslims are also theists. In order to show specifically that Christianity is true, as opposed to some other version of theism, we must do more. And the more that we must do takes us away from the purely rational and philosophical into the realm of history and empirical investigation. Space does not permit me to explore this area in any detail. Suffice it to say that Christian apologists have done an excellent job in defending the reliability of the Bible, especially where it deals with the life and teachings of the historical Jesus. Despite the skeptical attitudes of scholars like those in the infamous Jesus Seminar, there is every reason to trust the New Testament witness to Jesus. This witness informs us that Jesus claimed to be the Son of God, the promised Messiah who would save the world from sin. The New Testament also shows that he authenticated his claim by rising from the dead.

Jesus’ resurrection is supported by three virtually undisputed facts: (1) the empty tomb found on Sunday morning, (2) the appearances of Jesus to his disciples after his crucifixion, and (3) the startling belief of the early disciples in the resurrection of Jesus. The best and only plausible explanation for these facts is the truth that God raised Jesus from the dead.11

Christianity is Shown in Part by the Fact that None of the Objections to Christianity are Compelling

No reader of this article should come away thinking that there are no objections that a non-believer might raise to the Christian faith. Quite the contrary! There are innumerable objections that may and have been made to Christianity: the problem of evil, the alleged incoherence of the Trinity, alleged errors in the Bible, the supposed irrationality of belief in miracles, etc. All of these objections should be taken seriously and addressed as part of our project of showing that Christianity is true.

Dealing adequately with each of these objections would take articles and books of their own. Nevertheless, the Christian may take comfort from the knowledge that Christian scholars have in fact dealt adequately with these challenges. There have been many books and articles written to, as Calvin put it, “stop the mouths of the obstreperous.” After his masterful discussion of the major objections that can be brought against Christian belief, philosopher Alvin Plantinga wrote recently that “[N]one of these [objections]. . . presents a serious challenge to the warrant Christian belief can enjoy. . .”12 None of the objections to Christianity is without an adequate reply. None of the challenges to Christianity, in other words, present us with any compelling reason to abandon the faith.


How do we know that Christianity is true? We know it is true because God the Holy Spirit has made its truth known to us. Moreover, God has made available to us many philosophical arguments and historical evidences by which we can verify what the Holy Spirit witnesses to our hearts. Specifically, we may verify Christianity’s truth by the fact that no other worldview is rationally coherent; by the fact that there are powerful arguments that point us in the direction of the existence of God; by the fact that the historical data supports the life, death, and resurrection of Jesus; and by the fact that none of the objections that have been raised to the Christian faith are strong enough to compel us to abandon what the Holy Spirit has made known to us. Taken together, all of these facts allow us to say with certainty that we know that Christianity is true.

Steven B. Cowan is the Associate Director of the Apologetics Resource Center, and editor of Areopagus Journal.


1 See Craig’s discussion of this distinction in his Reasonable Faith (Wheaton: Crossway, 1994), 31-48; and “Classical Apologetics,” in Five Views on Apologetics, ed. Steven B. Cowan (Grand Rapids: Zondervan, 2000), 26-55.

2 Ibid., 32. It should be noted that none of this means that the internal testimony of the Spirit necessarily works apart from objective evidence of various kinds. For one thing, the testimony of the Spirit is itself objective evidence just as my sight of a tree is objective evidence for the belief that I see a tree. Moreover, the Spirit’s witness may accompany and confirm the evidence used in traditional apologetic arguments. But the Spirit’s witness goes beyond those arguments to provide an inner certitude that the arguments by themselves may not convey due to the blinding effects of sin that might keep one from rightly assessing those arguments.

3 It is important to distinguish what is being claimed here from the “burning bosom” defense used by Mormons. Followers of that cult often defend the authority of the Book of Mormon by claiming that sincere readers will receive a warm feeling in their bosom as they read the Book of Mormon, thus confirming its divine authority. But this is in no way analogous to the internal testimony of the Holy Spirit. For one thing, the internal testimony of the Spirit is not a physical feeling like a warm sensation in one’s chest. Rather, it is a mental state with a phenomenology more closely akin to the state one is in when he knows that 2+2=4, or he knows that he had toast for breakfast. Second, the Mormon uses his “burning bosom” as a premise in a dubious argument from religious experience. He argues in effect, “I have this burning sensation. Therefore, Mormonism is true.” This argument is used not only to convince the Mormon that his belief is true, but is used to persuade others as well. But, the internal testimony is not a premise in any argument, not even for the Christian. Nor is it used apologetically to convince others to accept Christianity. The internal testimony of the Spirit simply provides the Christian with an immediate, subjective certitude of the truth of Christianity. Third, as shown in the next section of the article, the Christian faith to which the Spirit testifies can also be shown to be true by historical and philosophical arguments. The Mormon faith, however, is incapable of such objective confirmation.

4 For more on the nature of worldviews see my article, “The Christian Worldview in Focus”, Radix 1:2 (April 2001): 13-19.
5 See Alvin Plantinga, Warrant and Proper Function (Oxford University Press, 1993), chap. 12; and Warranted Christian Belief (Oxford University Press, 2000), 227-240.
6 The Law of Non-Contradiction says that a proposition cannot be both true and false at the same time and in the same sense.
7 Paul Copan, “That’s Just Your Interpretation”: Responding to the Skeptics Who Challenge Your Faith (Grand Rapids: Baker, 2001), 53.
8 See William Lane Craig, Reasonable Faith, 91-122.
9 See Ibid., 116-117, for a more detailed discussion of this point.
10 For a more detailed defense of the Moral Argument see, Mark D. Linville, Is Everything Permitted? (Norcross, GA: Ravi Zacharias International Ministries, 2001).
11 For more on the historical evidence for the resurrection of Jesus and for the reliability of the New Testament, see, Michael Wilkins and J.P. Moreland, eds., Jesus Under Fire (Grand Rapids: Zondervan, 1995).
12 Plantinga, Warranted Christian Belief, 499.