Christianity claims to be true. Christians believe it to be true. But can the Christian know that it is true? Moreover, can the believer who cannot prove Christianity to be true, legitimately say that he knows that Christianity is true? Our purpose here is twofold: to show that the Christian can legitimately claim to know that Christianity is true, and to explore how the Christian knows.
Truth and Belief
Before exploring the subject of knowledge, we must first define truth and belief. Truth can be defined as “that which corresponds to or adequately expresses what is real.”1 This is most commonly referred to as the correspondence theory of truth, which says that something is true if it comports, or corresponds, with reality. Truth has to do with the real. A proposition or statement is true if it accurately describes reality.
Belief can be described as a positive cognitive acceptance of something to be true. Belief tends to be propositional. That is to say, when a person believes, he is taking a proposition to be true. For example, the proposition “there is a cat in the tree” may be true or false. If a person takes the proposition to be true, then that person holds the belief that the cat is in the tree. Obviously, if there really is a cat in the tree, the belief is true. But if there is no cat in the tree, the belief is false.
Belief that something is true must be distinguished from belief in a person or ideal. Belief in carries a meaning more akin to trust and somewhat similar to faith. Often, belief that must precede belief in. For example, to believe in God, one must first believe that God exists.
With truth and belief properly defined, some distinctions can be made. First and foremost, belief does not make something true. Belief is subjective and independent of the actual state of reality. Second, the basic definition of belief should not be confused with the common religious term of belief (a sort of religious commitment). To mix these terms will create misunderstanding and lead to false conclusions. Belief, in our current use, is cognitive acceptance of a proposition’s truth.
What is Knowledge?
There are various kinds of knowledge, such as knowing how to do something, or knowing a person. For our purposes, we are dealing with knowing that. This kind of propositional knowledge is most commonly defined as “justified true belief.” In other words, knowledge must meet three requirements: 1) the proposition must be believed; 2) the proposition must be true; and 3) the knower must have some degree of justification in their belief. This standard definition of knowledge is what we are dealing with when determining what we know.
To say that a person has good justification for their belief simply means that they have good or adequate reasons to accept that a thing is true. As philosophers William Lane Craig and J. P. Moreland explain:
…justification (or warrant) for a belief amounts to something like this: one has sufficient evidence for the belief, one formed and maintained the belief in a reliable way (e.g., on the basis of his senses or expert testimony and not by palm reading), or one’s intellectual and sensory faculties were functioning properly in a good intellectual environment when he formed the belief in question.2
So for something to meet the criteria of knowledge, not only must it be true and believed, but the person must have arrived at that belief not by unthinking happenstance, but by legitimate processes. Craig and Moreland continue: “Because it includes the notion of justification or warrant, [knowledge] involves believing what one epistemically ought to believe, believing what is right to believe, believing what it is intrinsically valuable or warranted to believe from an intellectual standpoint.”3
Knowledge and Certainty
Many may equate knowledge with the idea certainty. However, a very clear distinction must be made between knowledge and certainty. We can know what we are certain of, but certainty is not necessary for one to know. As Craig and Moreland explain:
If someone knows something, it does not necessarily mean that the person has complete certainty about that thing. “Being completely certain” in this context means “is logically impossible to be mistaken about.” This is a pretty high standard for knowledge. It requires it to be logically impossible for someone to be mistaken about
a claim before one can know the claim in question.4
If one requires certainty as a criterion for knowledge, one could soon be crippled in a quick descent into complete skepticism. In that case, one might even begin to doubt mathematical certainties through distrust of one’s own ability to reason. The seventeenth century French philosopher Rene Descartes doubted to the point of knowing only one thing for certain: that he was doubting, or thinking. Hence his dictum, “I think, therefore I am.” However, one need not embark upon a Cartesian quest for certainty in order to know a thing. Knowledge properly defined does not require full certainty.
Some things are known to varying degrees of certainty. As Francis Schaeffer observed, “we do not need to have exhaustive knowledge of a thing in order to know truly.”5 Some things are self-evidently known, such as the fundamental laws of logic. We know that A cannot equal non-A at the same time in the same manner. Mathematical truths are known with mathematical certainty. One could say that these are unquestionably true. One can know with certainty that they themselves exist; a truth that is actually undeniable. Yet other truths are known without any mathematical demonstration, such as certain moral truths. All people know particular things to be right or wrong, not through external proofs, but intuitively. We can know that we love and we can know that we are loved: “…simple knowing is still knowing even if it is not for certain.”6
Still, one may believe something to be true yet not claim to know that thing to be true. In such a case, probability plays a role in one’s process of justification. For example, one may have many good reasons to believe a proposition to be true, yet still have a few reasons to be tentative. In this case, one believes based upon an assessment of probability, but this reasonable probability does not warrant a claim to know. One might say that something is probably true, and therefore believe it without claiming to know.
And finally, all knowledge can be doubted – even certain knowledge. One may know something with certainty, yet doubt it if questioned by another. For example, suppose someone knows the date of his wedding anniversary. A friend questions this fact, causing him to momentarily doubt the specific date. Upon examination, he concludes that his knowledge was correct. Through the process of doubt, his knowing was confirmed through reflection and verification. Still, doubt does not equal lack of knowing.
What Does the Christian Claim to Know?
Christianity presents a comprehensive model of reality: a worldview. At its core, Christianity claims that God exists and Jesus is the savior of all who put their trust in him for salvation. For the believer to make a knowledge claim about Christianity is not to affirm every particular doctrine that could be constructed under a Christian system. Rather, when the believer says he knows Christianity is true, he is claiming to know particular central claims to be true, such as, “God exists,” and, “Jesus has saved me,” while also knowing the worldview as a whole is true. The Christian claims to know the central truths of the Gospel, while simply believing other basics based upon good reason.
How Can the Christian Know?
Depending on what one claims to know, there are different ways of knowing. Not all things are known the same way, through the same method. Knowledge is justified based on the nature of the claim. As Moreland points out, “what counts as adequate grounds will vary from circumstance to circumstance, depending on whether the context is art and beauty, chemistry, the reality of whether an event happened in history, knowledge that God is real, and so forth.”7
Some hurdles seem to appear along the path to knowing that God exists or that Christianity is true. The objections seem substantial enough. One could say that God’s existence cannot be proven; therefore one cannot know that he exists. One could also say that historical evidence is not clear enough to prove the resurrection of Christ without a doubt. In addition, it could be asserted that religious experiences of salvation can simply be reduced to an emotional event. However, the fact remains that just because a thing can be doubted does not mean it cannot be known.
Let us consider a few of the many factors that contribute to the overall case for the truth of Christianity. Factors such as the design and beauty of the universe, eyewitness testimony, historical events, personal experiences, and arguments from reason can give one adequate reasons and justification to believe that Christianity is true. However, even though these may be compelling, they may not be convincing. Christian evidences do not cause someone to know that God exists. They are adequate and reasonable grounds for one to believe that God exists or that Christianity is true, but independently they fall short of furnishing knowledge.
So how can the Christian know that God exists, that Christianity is true, and that Jesus has saved him? This knowledge comes by way of what is referred to as the inner witness of the Holy Spirit. The apostle Paul speaks of the inner knowledge that comes by the Holy Spirit upon conversion:
We have not received the spirit of the world but the Spirit who is from God, that we may understand what God has freely given us. This is what we speak, not in words taught us by human wisdom but in words taught by the Spirit, expressing spiritual truths in spiritual words. The man without the Spirit does not accept the things that come from the Spirit of God, for they are foolishness to him, and he cannot understand them, because they are spiritually discerned. (1 Corinthians 2:12-14 NIV)
Paul makes reference to the inner witness of the Holy Spirit in the heart of the believer again in Romans 8:16: “The Spirit himself testifies with our spirit that we are God’s children.” Moreover, the apostle John confirms this to be the case: “Anyone who believes in the Son of God has this testimony in his heart. … And this is the testimony: God has given us eternal life, and this life is in his Son.” (1 John 5:10-11 NIV) Craig explains the role of the Holy Spirit in the life of the believer:
“Thus, although arguments and evidence may be used to support the believer’s faith, they are never properly the basis of that faith. For the believer, God is not the conclusion of a syllogism; he is the living God of Abraham, Isaac, and Jacob dwelling within us. How then does the believer know that Christianity is true? He knows because of the self-authenticating witness of God’s Spirit who lives within him.”8
At this point one may object that if something cannot be verified to be true, then a knowledge claim cannot be warranted. However, remember that there are different ways of knowing. One way of knowing is by intuition, as is the case with much moral knowledge. Intuitively, we know that rape and child abuse are wrong. Although this cannot be externally proven, nevertheless it counts as valid knowledge. Yet objections may not be raised concerning moral knowledge, because it is often shared to a similar degree.
The problem that Christianity faces in claiming an inner witness of the Holy Spirit is that such knowledge cannot be externally proven. So can a knowledge claim that is not externally demonstrable be considered true knowledge?
Consider an example: suppose a savant (whom we’ll call Chris) is gifted with a profound and unique ability to make mathematical calculations without consciously processing the equations mentally. (Such savants, like British-born Daniel Tammet, are alive today.) And suppose a lengthy mathematical equation is presented to Chris. He immediately knows the answer, as he has a special endowment, or intuitive ability, to see the answer internally.
Now suppose someone without this endowment (whom we’ll call Skip), who knows nothing of this savant’s special ability, hears him claiming to “know” the answer. Instinctively, Skip may say, “You can’t know that.” But the only way Skip could prove Chris’s inner knowing to be illegitimate would be to produce a calculator proving the savant’s answer to be false. However, Chris does know the answer. In fact, the answer is mathematically certain. Surely, Chris is satisfied with knowing the answer, yet there is no external means to legitimize this method of inner knowing to the non-savant. The only resolution in this case would be to describe how this endowment functions.
The Inner Witness of Holy Spirit
So from the above examples we can see that it is not out of the question to suggest that the Christian can have an inner witness of the Holy Spirit. In fact, this seems reasonable. First, Christianity claims that this is how the believer knows he is a child of God. Second, Christians attest to the experiential reality of the inner witness of the Holy Spirit. And finally, not everyone has access to external evidences, compelling arguments, first-hand testimony, and the like. Assuming that God does exist, it seems reasonable for God to provide a sort of universal internal verification for those who are humbly seeking to know Him, yet do not have direct access to undeniable proof. The internal witness satisfies the believer with confident knowing, while not compelling the unbeliever.
In addition to the inner witness of the Holy Spirit for believers, the Bible speaks of the knowledge of God that has been given to all men. That is to say, Christianity claims that all men know that God exists, whether they acknowledge it to be true or not. Paul writes: “For since the creation of the world God’s invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that men are without excuse.” (Romans 1:20 NIV) This makes it clear that through a combination of inner knowledge and external evidence, men have sufficient means to know that God exists. As Schaeffer put it: “The Bible’s emphasis is that there are good and sufficient reasons to know that Christianity is true, so much so that we are disobedient and guilty if we do not believe it.”9 Craig concludes:
“Therefore, we find that for believers and unbelievers alike it is the self-authenticating work of the Holy Spirit that supplies knowledge of Christianity’s truth. …And because this belief is formed in response to the self-disclosure of God himself, who needs no external authentication, it is not merely rational for us, but constitutes knowledge. We can be confident of Christianity’s truth.”10
Inner knowledge of God has been granted to all men, although Paul indicates that men “…suppress the truth by their wickedness, since what may be known about God is plain to them, because God has made it plain to them.” (Romans 1:18-19 NIV) This knowledge of the truth can be suppressed. Nevertheless, this knowledge serves to “level the playing field,” so to speak, so that all men have equal access to know God, no matter where they may be born or the evidence and information available to them. Not everyone has access to the evidences, but all have access to the Spirit.
Can the Christian Know?
So can the Christian know? Yes, the Christian can know not only that God exists, but that he is saved, and that Christianity is true. Moreover, his mind has been awakened to discern and understand spiritual truths. The Christian who loves the truth seeks to verify and authenticate the truthfulness of Christianity in order to gain confidence and understanding. Although demonstrable certainty is not attainable in this life, inner certitude is, as philosopher Norman Geisler points out:
Certainty…is in principle impossible when we are dealing with matters of experience, a part of which is the resurrection and our experience of saving grace. However, the reason that God demands total and unconditional commitment and that the believer holds so tenaciously to his belief in God and His love is that the believer has certitude concerning these beliefs. Certitude is that added assurance given to the believer by the internal witness or testimony of the Holy Spirit. God’s Spirit bears witness with our spirit to the truth of spiritual matters.11
The unbeliever has an intrinsic knowledge of God. Coupled with the evidence of creation and conscience, the humble man believes that God exists. In response to the Gospel and by the work of the Holy Spirit, he puts his faith (trust) in Jesus Christ for salvation. God regenerates the believer and through the inner witness Holy Spirit, the Christian knows he is saved. As Craig concludes, “We know Christianity is true primarily by the self-authenticating witness of God’s Spirit. We show Christianity is true by demonstrating that it is systematically consistent.”12 Through examination of evidences, the believer finds that Christianity is consistent, coherent, and complete as a worldview. For the Christian, faith is not a leap in the dark. Faith is trusting in that which one does not see, on the basis of what one has good reasons to believe and know to be true.
1 C. Steven Evans, Pocket Dictionary of Apologetics & Philosophy of Religion (Downers Grove, IL: InterVarsity Press, 2002), p. 118.
2 J. P. Moreland and William Lane Craig, Philosophical Foundations for a Christian Worldview (Downers Grove, IL: InterVarsity Press, 2003), p. 74.
3 Ibid., p. 83.
4 Ibid., p. 84.
5 Francis Schaeffer, Trilogy: He Is There And He Is Not Silent (Wheaton, IL: Crossway Books, 1972), p. 331.
6 Craig and Moreland, p. 85.
7 J. P. Moreland, The Kingdom Triangle (Grand Rapids, MI: Zondervan, 2007), p. 130.
8 William Lane Craig, Reasonable Faith (Wheaton, IL: Crossway Books, 1994), p. 34.
9 Francis Schaeffer, Trilogy: The God Who Is There (Wheaton, IL: Crossway Books, 1968), p. 178.
10 Craig, p. 36.
11 Norman Geisler and Paul Feinberg, Introduction to Philosophy: A Christian Perspective (Grand Rapids, MI: Baker Books, 1980), p. 131.
12 Craig, p. 48.