Theological rationalism is the view that, generally speaking, the only way to have rational confidence in the truth of Christianity is by looking at the public evidence. What distinguishes a theological rationalist from a secular rationalist is that the former believes there is sufficient evidence to rationally warrant, or even compel, belief in the truth of the gospel for the man who is fully informed, whereas the latter does not. This stands in stark contrast to the paradigm, often referred to as “reformed epistemology”, which holds that one can be rationally warranted in believing Christianity to be true wholly apart from public evidence and argument. Reformed epistemology is not at all limited to fideists and presuppositional apologists. Even many classical apologists, notably William Lane Craig, frequently draw a distinction between how you know that your faith is true, and how you show to others that your faith is true. On how Dr. Craig personally knows his faith to be true, he is quite candid in saying that he is not an evidentialist. Dr. Craig states that he knows his faith is true because of the internal witness of the Holy Spirit, which imparts to him confidence that Christianity is true. Since other people do not have access to his own personal subjective experience, Dr. Craig appeals to public evidences to demonstrate to others that his faith is true – but, importantly, Dr. Craig’s own personal faith apparently does not rest on those evidences.
Even among apologists, sadly, theological rationalism is very much a minority position, and I would like to see it promoted more widely. In this article, I want to address some popular concerns about theological rationalism and provide clarity about what my view is and contrast it with popular misconceptions. I will begin by offering a brief positive case for adopting theological rationalism, and will then offer responses to 12 popular concerns or objections that I encounter frequently from other Christians.
The Biblical Case for an Evidential Faith
Throughout Scripture, we see evidentialism modeled by the prophets, by the apostles, by Jesus, and by Yahweh himself in the Old Testament.
For example, consider Isaiah 45:20-21:
20 “Assemble yourselves and come; draw near together, you survivors of the nations! They have no knowledge who carry about their wooden idols, and keep on praying to a god that cannot save. 21 Declare and present your case; let them take counsel together! Who told this long ago? Who declared it of old? Was it not I, the Lord? And there is no other god besides me, a righteous God and a Savior; there is none besides me.
And Isaiah 48:3-5:
3 “The former things I declared of old; they went out from my mouth, and I announced them; then suddenly I did them, and they came to pass. 4 Because I know that you are obstinate, and your neck is an iron sinew and your forehead brass, 5 I declared them to you from of old, before they came to pass I announced them to you, lest you should say, ‘My idol did them, my carved image and my metal image commanded them.’
In both of those texts in Isaiah, Yahweh invites those who worship false gods, which are “wooden idols”, to “Declare and present your case” for those idols really being true gods. Yahweh supplies his own evidence to establish His existence and primacy – namely, that He alone is the one who declares things before they come to pass. Only Yahweh can predict the future.
There are many Old Testament texts that could be used in support of the evidentialist method. To take one further example, consider Exodus 4:1-9, in which Yahweh equipped Moses with miraculous signs as evidence that would persuade the Hebrews that he really was sent by God:
Then Moses answered, “But behold, they will not believe me or listen to my voice, for they will say, ‘The Lord did not appear to you.’” 2 The Lord said to him, “What is that in your hand?” He said, “A staff.” 3 And he said, “Throw it on the ground.” So he threw it on the ground, and it became a serpent, and Moses ran from it. 4 But the Lord said to Moses, “Put out your hand and catch it by the tail”—so he put out his hand and caught it, and it became a staff in his hand— 5 “that they may believe that the Lord, the God of their fathers, the God of Abraham, the God of Isaac, and the God of Jacob, has appeared to you.” 6 Again, the Lord said to him, “Put your hand inside your cloak.” And he put his hand inside his cloak, and when he took it out, behold, his hand was leprous like snow. 7 Then God said, “Put your hand back inside your cloak.” So he put his hand back inside his cloak, and when he took it out, behold, it was restored like the rest of his flesh. 8 “If they will not believe you,” God said, “or listen to the first sign, they may believe the latter sign. 9 If they will not believe even these two signs or listen to your voice, you shall take some water from the Nile and pour it on the dry ground, and the water that you shall take from the Nile will become blood on the dry ground.”
Even in the Proverbs, we are counselled to be rational in determining what to believe. Consider, for example, Proverbs 14:15: “The simple believes everything, but the prudent gives thought to his steps.”
Turning over to the New Testament, we also see plenty of examples of Jesus utilizing evidences in order to support His Messianic credentials. For example, when John the Baptist sent messengers to Jesus to ask Him whether He was the one they were expecting, take note of Jesus’ reply (Matthew 11:4-6):
4 And Jesus answered them, “Go and tell John what you hear and see: 5 the blind receive their sight and the lame walk, lepers are cleansed and the deaf hear, and the dead are raised up, and the poor have good news preached to them. 6 And blessed is the one who is not offended by me.”
In other words, Jesus pointed to His miracles as public evidence that demonstrated that He was indeed God’s Messiah, the one that the children of Israel had long been waiting for.
To take one further example from Jesus, after Jesus cleanses the temple in John 2, the Jews ask Jesus, “What sign do you show us for doing these things?” (verse 18). Note Jesus’ reply (verses 19-22):
19 Jesus answered them, “Destroy this temple, and in three days I will raise it up.” 20 The Jews then said, “It has taken forty-six years to build this temple, and will you raise it up in three days?” 21 But he was speaking about the temple of his body. 22 When therefore he was raised from the dead, his disciples remembered that he had said this, and they believed the Scripture and the word that Jesus had spoken.
Thus, Jesus points to His resurrection from the dead as the vindication of His authority over the temple of God.
The apostles also used their eyewitness testimony of Jesus’ resurrection, as well as the fulfilment of Messianic prophecy in Jesus, as evidence in support of their claims. For example, Peter, addressing the Jews at Pentecost, said, “This Jesus God raised up, and of that we all are witnesses.” Likewise, Paul, addressing the Areopagus (Acts 17:31), declared,
he has fixed a day on which he will judge the world in righteousness by a man whom he has appointed; and of this he has given assurance to all by raising him from the dead.”
Turning over to the epistles, we see Paul telling us that mankind is rendered without excuse (Greek, anapologētous, literally “without an apologetic”) before God because God’s eternal power and divine nature have been clearly revealed through what God has made (Romans 1:20). In other words, it is the evidence from creation that renders men without an apologetic.
One could go on, but these examples ought to be more than sufficient to demonstrate the evidential and rational character of the Christian faith. Now, let us turn to an assessment of the extent to which personal subjective religious experience may be used as evidence for the veracity of one’s Christian faith. Let me conclude this section with a quote from a Scotsman, George Campbell [A Dissertation on Miracles (Edinburgh: A. Kincaid & J. Bell, 1762), pp. 1-4.]:
“Christianity,” it hath been said, “is not founded in argument.” If it were only meant by these words, that the religion of Jesus could not, by the single aid of reasoning, produce its full effect upon the heart; every true Christian would cheerfully subscribe to them. No arguments unaccompanied by the influence of the Holy Spirit, can convert the soul from sin to God; though even to such conversion, arguments are, by the agency of the Spirit, render’d subservient. Again, if we were to understand by this aphorism, that the principles of our religion could never have been discover’d, by the natural and unassisted faculties of man; this position, I presume, would be as little disputed as the former. But if, on the contrary, under the cover of an ambiguous expression, it is intended to insinuate, that those principles, from their very nature, can admit no rational evidence of their truth, (and this, by the way, is the only meaning which can avail our antagonists) the gospel, as well as common sense, loudly reclaims against it.
The Lord Jesus Christ, the author of our religion, often argu’d, both with his disciples and with his adversaries, as with reasonable men, on the principles of reason. Without this faculty, he well knew, they could not be susceptible either of religion or of law. He argu’d from prophecy, and the conformity of the event to the prediction. He argu’d from the testimony of John the Baptist, who was generally acknowledged to be a prophet. He argu’d from the miracles which he himself perform’d, as uncontrovertible evidences, that God Almighty operated by him, and had sent him. He expostulates with his enemies, that they did not use their reason on this subject. Why, says he, even of yourselves, judge ye not what is right? In like manner we are called upon by the apostles of our Lord, to act the part of wise men, and judge impartially of what they say. Those who do so, are highly commended, for the candour and prudence they discover, in an affair of so great consequence. We are even commanded, to be always ready to give an answer to every man, that asketh us a reason of our hope; in meekness to instruct them that oppose themselves; and earnestly to contend for the faith which was once delivered to the saints. God has neither in natural nor reveal’d religion, left himself without a witness; but has in both given moral and external evidence, sufficient to convince the impartial, to silence the gainsayer, and to render the atheist and the unbeliever without excuse. This evidence it is our duty to attend to, and candidly to examine. We must prove all things, as we are expressly enjoin’d in holy writ, if we would ever hope to hold fast that which is good.
Can we rely on personal experience as a rational warrant for belief?
The equation given below represents the odds form of Bayes theorem, which is used in developing cumulative cases. Translated, it states that the posterior probability of your hypothesis (H) given the available evidence (E) is equal to the prior probability (given the background information) of the hypothesis being true (expressed as a ratio) multiplied by the ratio of the evidence given the hypothesis against the probability of the evidence given the antithesis.
Dividing the probability of the evidence given the hypothesis by the probability of the evidence given the antithesis gives you what is referred to in probability theory as the Bayes Factor. The Bayes Factor is a measure of the strength of the evidence, and indicates how many times more likely it is that you will observe this evidence given that your hypothesis is true than if it were false. For instance, a Bayes Factor of one hundred indicates that your evidence is one hundred times more likely if your hypothesis is true than if it were false.
This form of reasoning is used routinely in the discipline of forensic science. For instance, the presence of a defendant’s finger prints on the murder weapon may be taken as evidence for the hypothesis of guilt over the hypothesis of non-guilt because the probability of the defendant’s finger prints being on the murder weapon is much higher on the hypothesis that the defendant is guilty than on the hypothesis that he is not guilty. This is the very same mode of reasoning that I use when evaluating the evidence for the existence of God and for the truth of the Christian gospel.
Now, how might we use Bayes’ Theorem to evaluate the evidential value of a personal subjective experience? Let’s suppose, generously for argument’s sake, that your personal subjective experience is twice as likely if Christianity is true than if it is false. That means your Bayes Factor is 2. Let’s also assume, again generously, that there are no background considerations and thus the prior probability of Christianity being true is 0.5, or a 1:1 ratio. That would justify a move in confidence in Christianity’s truth from 0.5 to 0.6667. If we suppose that the prior odds are a bit lower than 0.5, and assume a prior probability of 0.4444 (4:5 ratio), then the posterior probability comes out at only 0.61.
In view of this, it seems that personal subjective experience is unlikely to contribute substantially to our warranted confidence in Christianity’s truth. For one thing, it is unlikely to have a high Bayes Factor (I think a Bayes Factor of 2 was being extremely generous). The fact that people of all sorts of religious traditions (which cannot all be right) claim personal subjective experience suggests that the Bayes Factor is in fact quite small. Furthermore, the ability of illusionists and hypnotists (such as Derren Brown – e.g. see or ) to, through psychological techniques, replicate subjective experiences, such as a sense of the presence of God, also supports this further. Second, even with a high Bayes Factor, a sufficiently small prior probability is sufficient to overcome even very strong evidence. Therefore, the background probability cannot be ignored, and I see no way to get a handle on the prior odds except by investigation of the relevant arguments and public evidences.
That being said, while, as I have already noted, the Bayes Factor for personal subjective religious experience is not usually high, the prior probability is dramatically increased by the public evidence (which here constitutes the background information). Hence, one is reasonable in interpreting such personal experience in view of Christianity as a result of having independent confidence in Christianity’s truth. Furthermore, we also believe in general providence, so even experiences that "just" come to us because of emotions or psychological phenomena (e.g. a sense of peace or joy) are in some sense within God's plan and hence God can be thanked for them.
I should note that I do think that, in principle, appeals to private subjective experience could be a valid approach. For instance, suppose that whenever someone became a believer, there was a voice from heaven, only heard by the new believer, that said "Welcome to the family." That, I think, would be rational warrant for affirming Christianity to be true -- even though you would need to appeal to public evidence in order to demonstrate to others that Christianity is true. I also don’t want to discount that veridical, i.e. truth-attesting, subjective experiences, do exist in the world. However, I myself have no such veridical experiences to speak of. Thus, for me, my faith in Christ rests on the public evidence alone, and not on any personal subjective experience.
Answered prayer is another piece of subjective evidence often asserted to warrant belief, and again, I think this could be a valid approach in principle. However, to use it as belief-warranting evidence, one would have to demonstrate a statistical significance to answered prayer, in order to distinguish it from mere coincidence. All Christians who pray can speak of times where they have requested something in prayer where they have not received what they asked for. There are a number of explanations given for this in Scripture. For example, prayer can be hindered by sin (Proverbs 28:9, 1 Peter 3:7) or by selfish-intent (James 4:3), and sometimes God knows that what we ask for is not good for us, and often his will and purpose is different from ours. All these potential variables make it difficult to use answered or unanswered prayer as evidence for or against the Christian faith. If fulfilled prayer is to be used as evidence for the truth of Christianity, one must be able to specify a hypothetical outcome which in principle could be dis-confirmatory evidence. This makes arguing from fulfilled prayer complicated.
Is the Beauty of the Gospel Sufficient Warrant for Believing it to be True?
Some reformed epistemologists, such as Dr. John Piper, and before him Jonathan Edwards, have argued that the portrayal of God's glory in Scripture, or the beauty of the gospel, are sufficient grounds to warrant belief -- and not just that, but to warrant belief with absolute certainty (e.g. see chapters 8-17 of Piper's A Peculiar Glory). Space and time do not permit me to write a thorough rebuttal to Dr. Piper's argument in the book (if we can even call it an argument). I read through Piper's remarks carefully, and I am afraid that Dr. Piper offered no justification for his assertion that the glory of God portrayed in Scripture is sufficient ground for epistemic certainty in the gospel's truth. While the beauty of the gospel may be a clue, it is wrongheaded to think that this will give lasting certainty. To assert that is to confuse psychological and epistemic certainty. The psychological kind of certainty, though it can be momentarily overwhelming, is not stable. To rest one's faith upon a psychological ground is to court disaster. Ironically, Dr. Piper states that a shortcoming of the historical-critical method is that it produces only probable results, and cannot impart certainty. But he fails to explain how the method that he advocates can impart greater certainty.
Furthermore, how would one respond to a Muslim making a similar appeal? A popular Muslim argument is from the unparalleled beauty of the Qur'an. But it doesn't logically follow (even granting the premise) that the Qur'an is in fact true.
Having given a brief argument for being a theological rationalist, let me now respond to some popular concerns that I frequently encounter from other believers.
Concern #1: Theological rationalism downplays the role of the Holy Spirit in conversion.
It is sometimes alleged that the view that I am here advocating downplays the role of the Holy Spirit in conversion. But this isn’t the case, for it erects a false dichotomy. Rather, in my view, the Holy Spirit works through the presentation of arguments and public evidences, in order to draw men unto God. It is not my position that the arguments and evidences themselves are sufficient to bring about regeneration, but rather that they must be accompanied by the work of the Spirit of God. This objection is rather akin to a hyper-Calvinist’s protest against the need for a Christian to participate in evangelism. If it is ultimately God’s Spirit who draws His elect into the kingdom, the hyper-Calvinist asks, then what is the need for Christians to engage in evangelism, since God has no need of us? The answer to this of course is that we should be engaged in evangelism in obedience to the great commission, and that God in his grace has chosen to use us as vehicles and instruments for the spread of the gospel – it is not that we do evangelism apart from God’s Spirit, but rather we do it accompanied by God’s Spirit. If we reject hyper-Calvinism, then this objection lacks a consistent basis.
Concern #2: Theological rationalism implies that the Spirit cannot work through preaching of the Word, unless that preaching is accompanied by presentation of argument and evidence.
While presentation of public evidence and argument is one means by which the Holy Spirit can work, I do not believe that it is the only way that He works. I do believe that there is power in the declaration of the Word of God, even apart from evidence. However, the message of the gospel should never be presented in a way that gives the misimpression that the belief required is without (or in defiance of) the public evidence. Moreover, following conversion, an important part of the process of Christian discipleship should involve the study of Christian evidences and the rational basis for our faith.
Concern #3: Theological rationalism consigns Christians who lack the intelligence or education to understand the public evidences to irrationality.
It is often asserted in response to the method of apologetics that I advocate that it consigns many Christian men and women to irrationality. For not everyone has the intelligence or education to understand the various arguments and evidences for Christianity. This is an objection frequently given by William Lane Craig. However, this need not be the case, since it is possible to have a tacit or implicit rational warrant for one's Christian beliefs. For example, one might read the Scriptures and intuitively recognize their verisimilitude, and the fulfilment of Old Testament Scripture, such as Isaiah 53, in the person of Jesus Christ. Their rational warrant may not be well developed, and they may not be able to articulate it cogently to others, or answer scholarly objections. Nonetheless, I believe that a tacit apologetic for belief counts as a rational warrant for Christian faith. However, one must not be content to stay there. As previously stated, part of the process of attaining spiritual maturity, for any believer, is to grow in one's understanding of Christian evidences. The level and depth of apologetics will of course vary from individual to individual.
Concern #4: Theological rationalism downplays the doctrine of the total depravity of man.
Another popular objection is that theological rationalism does not take account of the Biblical portrayal of anthropology, where man is an active suppressor of what is evident about God though creation (Romans 1:18-20) and conscience (Romans 2:15), and as such he is unable to submit to God unless enabled to by the Holy Spirit (Romans 8:7-8). This concern, however, again misses that the evidence for the truth of Christianity is to be presented accompanied by, rather than apart from, the Holy Spirit. The presentation of the gospel and its evidences to any non-believer must be backed up by time spent before the Lord in prayer, for unless God is in it we may as well be trying to reason with a dead man, for man without the Spirit remains dead in transgressions and sins (Ephesians 2:1).
Concern #5: Theological rationalism results in a dry form of Christianity without any emotion or intimacy with God.
This certainly isn’t true. Rather, the position that I advocate is merely that emotion and intimacy with God are not veridical – that is to say, they do not rationally warrant belief in Christianity’s truth. Emotion is something which should follow belief, not create belief. For me, the more intellectually convinced I am of Christianity’s truth; the more emotion I experience about my faith, the more I feel conviction over sin, and the more I desire to pursue greater intimacy with God. But these things do not compel me to believe Christianity is true. On the contrary, they flow out of my persuasion that Christianity is true.
Concern #6: The faith of a theological rationalist is in a constant state of flux, as his faith is tossed to-and-fro by the continually shifting sands of evidence.
It is often asserted that the faith of a theological rationalist is unstable, for if the evidence on the basis of which he has trusted Christ turns out to be rather less convincing than he first thought, or if fresh counter-evidence comes to light, his faith will be significantly shaken. The extent of the evidence in which my faith is grounded, however, means that my faith is not immediately perturbed by encountering fresh counter-evidence or arguments that I have not previously been exposed to (in much the same way that a well supported scientific theory is seldom overturned by a single anomalous observation). Rather, new counter-evidence is to be understood within the context of the available data taken as a whole.
Likewise, my faith is not perturbed if some of the evidence on which my faith rests turns out, in the course of time, to be less strong than I presently believe (in much the same way that the discovery that some of the evidence for the earth's vast age, or the evidence that Julius Caesar crossed the Rubicon, or the evidence that Abraham Lincoln existed, was weaker than I previously thought would not seriously cause me to doubt the conclusion, which would still be supported by significant other public evidence).
For these reasons, even though I ground my personal faith in the public evidence (and not in subjective internal experience) my confidence in my faith is not tossed to-and-fro by the shifting sands of evidence. On the other hand, by contrast, the man who has not invested any time in investigating the reasons for our faith, and who has built his faith on the sand of emotion, is much more likely to be shaken if and when he encounters intellectual objections to the Christian faith from a learned atheist. Furthermore, if and when it is shown that psychological phenomena are sufficient to explain one’s personal subjective religious experiences (if this is what he anchors his confidence in), this could also cause one to have doubts about the truth of Christianity.
Concern #7: Public evidence cannot deliver certainty about the truth of Christianity – at most it can only show that there is a high probability of Christianity being true.
There are two senses in which one can speak about certainty. First, there is mathematical or deductive certainty, which is really only attainable in pure mathematics (e.g. there is mathematical certainty that 2+2 = 4). Valid deductive logic can also provide this form of certainty, but only insofar as the premises of the argument are true (and those premises themselves may be subject to uncertainty). The French philosopher René Descartes (1596-1650) also famously showed that we can be certain of our own existence, even if we can’t be about the existence of the external world, since to doubt one’s own existence implies that there is in fact one to do the doubting. Beyond those things, there is nothing in this life of which we can be absolutely certain in this first sense. We cannot even be certain that the external world exists, or that the Universe was not created 5 minutes ago with the appearance of age. But we are nonetheless rational in holding to those beliefs, and irrational not to.
In a court of law, the prosecution does not need to establish this first form of certainty in order to convict a defendant. Rather, the standard that is used is certainty beyond a reasonable doubt. I am not certain in the rigorous sense that Julius Caesar crossed the Rubicon, or that Alexander the Great existed, or that the earth is billions of years old. But I am certain beyond reasonable doubt of those things. Likewise, I am not certain in a strict mathematical or deductive sense that Christianity is true, but I would say I am certain beyond reasonable doubt (one might say my confidence is 0.9999).
I fail to see how any other method could yield better certainty. Assuredly, trusting personal experiences cannot grant you certainty in the technical rigorous sense.
Concern #8: Theological rationalism implies that you have to be able to answer every objection before you can be rational in believing it.
The existence of unanswered questions is not at all grounds for rejecting a system of thought, for every belief system has its share of unanswered and difficult questions. The question is, rather, are there better, more substantive, and more numerous objections to belief or to non-belief? Considering all of the relevant information, where does the balance of evidence lie?
Let me quote wise words from 19th century English theologian Richard Whately’s Elements of Logic, 9th ed. (London: Longmans, Green, Reader, & Dyer, 1870), pp. 144-45:
“Similar to this case is that which may be called the Fallacy of objections; i.e. showing that there are objections against some plan, theory, or system, and thence inferring that it should be rejected; when that which ought to have been proved is, that there are more, or stronger objections, against the receiving than the rejecting of it.
This is the main, and almost universal Fallacy of anti-christians; and is that of which a young Christian should be first and principally warned. They find numerous ‘objections’ against various parts of Scripture; to some of which no satisfactory answer can be given; and the incautious hearer is apt, while his attention is fixed on these, to forget that there are infinitely more, and stronger objections against the supposition, that the Christian Religion is of human origin; and that where we cannot answer all objections, we are bound, in reason and in candour, to adopt the hypothesis which labours under the least.
That the case is as I have stated, I am authorized to assume, from this circumstance,—that no complete and consistent account has ever been given of the manner in which the Christian Religion, supposing it a human contrivance, could have arisen and prevailed as it did. And yet this may obviously be demanded with the utmost fairness of those who deny its divine origin. The Religion exists; that is the phenomenon. Those who will not allow it to have come from God, are bound to solve the phenomenon on some other hypothesis less open to objections. They are not, indeed, called on to prove that it actually did arise in this or that way; but to suggest (consistently with acknowledged facts) some probable way in which it may have arisen, reconcilable with all the circumstances of the case. That infidels have never done this, though they have had 1800 years to try, amounts to a confession, that no such hypothesis can be devised, which will not be open to greater objections than lie against Christianity.”
One can thus be very rational in putting his faith in Christ even with as-yet unresolved questions and difficulties. While there are no-doubt objections to the Christian faith, rejection of the Christian faith opens up much more substantive and much more numerous objections. Therefore, we ought rationally to prefer to believe in Christianity. Care must be taken not to be so taken up with the objections that we miss the forest for the trees, and miss the avalanche of confirmatory evidence of the gospel’s truth.
Concern #9: Theological rationalism undermines the doctrine of the sufficiency of Scripture.
It is sometimes alleged that the methods I advocate for demonstrating Christianity to be true undermine the reformed doctrine of the sufficiency of Scripture. However, normally when we speak of the sufficiency of Scripture we mean that Scripture is sufficient to provide us with all of the information necessary to know and receive the gospel, and to equip us for a life of faith and service. We of course do not mean that Scripture has a monopoly on all that can be known, or that the meaning and significance of various Biblical texts cannot be helpfully illuminated or corroborated by extra-Biblical sources. If the preference of the one making this objection is to assert the Bible to be the Word of God by virtue of the fact that it claims to be, then this is to reason in a circle. Why should we believe in the sufficiency of Scripture? First, we have to establish it as an authority – but I see no way to do this apart from grounding such a conclusion in public evidence.
In any case, I think that Scripture itself provides us with sufficient criteria to establish its veracity, for many of my criteria for assessing the Bible derive directly from the text of Scripture itself. Recall the texts from Isaiah I mentioned earlier in this article where Yahweh challenges the idols to accurately predict the future ahead of time. Thus, the criterion of fulfilled prophecy is a criterion supplied by Scripture itself as a means of determining its supernatural origin. Furthermore, Messianic prophecy is a criterion used by Jesus to support His own credentials, and was used, along with the eyewitness testimony to the resurrection, by the early apostles in the book of Acts in order to show that Jesus is the Jewish Messiah. Thus, quite a number of the criteria that I would use to establish the truth of Christianity are already supplied within the text of Scripture itself.
Concern #10: By evaluating Scripture by argument and evidence, one sets oneself as the authority over Scripture, rather than the reverse.
It is often asserted that, by using argument and evidence to evaluate the Scriptures, one sets oneself up as the authority over Scripture, when in fact a Christian ought to be in submission to Scripture. An illustration sometimes given, notably by the Van Tilian presuppositionalist Sye Ten Bruggencate, is that arguments and evidences are normally presented to a judge and jury, and thus, by presenting the unbeliever with arguments and evidences he is giving the misimpression that the unbeliever is the judge and God is the one on trial, when in reality it is the other way round: the sinner is the one on trial and God is the judge. I think a different analogy might be more fitting here, however. Rather than imagining a courtroom, picture a doctor informing his patient that he has some life-threatening disease. The doctor might show the patient some X-rays, as evidence for the disease, and recommend a course of treatment, perhaps showing him the evidence for the treatment’s effectiveness. When the patient begins to undergo the treatment, he is submitting himself to that treatment. In like-manner, men and women have a spiritually terminal disease called sin, and the only way to be saved is through trusting in Jesus Christ. When one comes to recognise this and takes Christ as his saviour, he at that point submits himself to Christ’s Lordship. But he must first come to recognise that Jesus really is the way of salvation, and I think presentation of evidence and argument is a legitimate way to demonstrate this to people. I think a quote from Thomas Chalmers will be of value here [The Evidence and Authority of the Christian Revelation, 4th ed. (1817, pp.275-77)]:
"Reason can judge of the external evidences for Christianity, because it can discern the merits of human testimony: and it can perceive the truth or the falsehood of such obvious credentials as the performance of a miracle, or the fulfilment of a prophecy.... [But a]fter we have established Christianity to be an authentic message from God upon those historical grounds, on which the reason and experience of man entitle him to form his conclusions, nothing remains for us but an unconditional surrender of the mind to the subject of the message. We have a right to sit in judgment over the credentials of heaven's ambassador, but we have no right to sit in judgment over the information he gives us."
Concern #11: Don’t theological rationalists believe only those Biblical truths for which there is confirmatory evidence? What about those assertions of the Bible for which there is no or little evidence?
One does not need to demonstrate the truth of every proposition in Scripture in order to have a rational confidence in their truth. It is perfectly valid to argue inductively that the Biblical documents are substantially trustworthy sources and thus we can trust them to accurately report even those events that we cannot corroborate or confirm. In other words, if all of the things that we can cross-check the sources on turn out to be true and accurate, then that is prima facie reason for trusting those documents concerning those things which we cannot cross-check.
Another important point is that if, as I maintain, the evidences concerning Jesus’ identity indicate His divine status, then that is prima facie reason for trusting those things stated by Jesus. Since Jesus affirms the Torah, prophets, Psalms and historical literature of the Old Testament to be reliable, and even divinely inspired, that may be taken as indirect evidence in support of those Scriptures.
I would also argue that there is evidence to support Paul’s commissioning by Jesus to the role of apostle, which gives the teaching in his epistles the authority of Christ Himself. The apostle Paul affirmed in 2 Timothy 3:16-17 that,
16 All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, 17 that the man of God may be complete, equipped for every good work.
Therefore, since Christ has put his stamp of approval on Paul as an apostle of God, we ought also, like Paul, to understand all Scripture to be breathed out by God.
Concern #12: Doesn’t Theological Rationalism Conflict with Certain Biblical Passages?
Several Biblical texts are sometimes cited by those criticising theological rationalism. One example is Isaiah 55:8-9:
8 For my thoughts are not your thoughts, neither are your ways my ways, declares the Lord. 9 For as the heavens are higher than the earth, so are my ways higher than your ways and my thoughts than your thoughts.
Unfortunately, this is one of the most decontextualized texts in Scripture. It is often assumed that the “your” of these verses refers to the reader. However, the antecedent of the pronoun becomes evident when one reads the immediately preceding verse (verse 7):
let the wicked forsake his way, and the unrighteous man his thoughts; let him return to the Lord, that he may have compassion on him, and to our God, for he will abundantly pardon
Thus, Isaiah 55:8-9 is not a statement about logic and reason, but rather it is a statement about morality. God is saying that his thoughts are not the thoughts of the wicked and unrighteous, nor his ways their ways.
Turning over to the New Testament, we encounter 1 Corinthians 1:21 and 2:4-5:
For since, in the wisdom of God, the world did not know God through wisdom, it pleased God through the folly of what we preach to save those who believe… My speech and my message were not in plausible words of wisdom, but in demonstration of the Spirit and of power, so that your faith might not rest in the wisdom of men but in the power of God.
The contrast that Paul is here drawing is not, as some might have it, with sound thinking and public evidence. Instead, Paul contrasts his approach with mere persuasive rhetoric designed to impress. Paul is decrying pagan philosophy, not philosophy as a discipline for pursuing an epistemically justified faith. Paul tells us that the problem is that through that sort of wisdom the world did not know God (1 Corinthians 1:21). There is indeed a need for special revelation, for without it we could not know the truths of the gospel. Special revelation, however, can be attested by historical evidences including miraculous signs. Paul’s decrying of inadequate philosophy is no reason to indict philosophical arguments for the existence and nature of God.
Another text that is sometimes brought up is Hebrews 11:1-3:
Now faith is the assurance of things hoped for, the conviction of things not seen. 2 For by it the people of old received their commendation. 3 By faith we understand that the universe was created by the word of God, so that what is seen was not made out of things that are visible.
This text is often used to argue that Biblical faith is blind. However, a careful read of Hebrews 11 reveals quite the opposite. The individuals listed in the great faith hall of fame all had one thing in common – they responded to evidence of God’s character by trusting Him with promises not yet fulfilled. This illuminates the meaning of Hebrews 11:1. Faith is the assurance of things hoped for – that is, the assurance that God will fulfil His promises for the future – the conviction of things not seen, since the future is not yet seen to us. One might say that I have faith in the Hebrews 11:1 sense that the sun will rise tomorrow morning – not because I have seen the sun rise tomorrow (it hasn’t happened yet), but because I have experience of the sun rising every morning in the past, and so I have a rational justification for believing that the sun will rise again tomorrow. In like-manner, the saints of old trusted God with His future promises, which they hadn’t yet seen fulfilled, because they had evidence for God’s faithfulness in the past.
A yet further text that is frequently raised is John 20:29, in which Jesus speaks to Thomas, after Thomas has recognised Jesus as His Lord and God:
Jesus said to him, “Have you believed because you have seen me? Blessed are those who have not seen and yet have believed.”
Again, this text is used to support that the Bible commends blind faith without any evidence. However, again, this is simply a misreading of the text. Jesus is rebuking Thomas for not having trusted the eyewitness testimony of the other disciples – that testimony in itself should have been evidence enough for Thomas. In any case, visual evidence is not the only category of evidence that can be used to support a claim. In the case of Jesus’ resurrection, none of us living in the present has seen the risen Lord. However, we do nonetheless have a strong circumstantial historiographical case for Jesus’ resurrection.
Another important text that has been brought up in such discussions is 2 Corinthians 4:6:
For God, who said, “Let light shine out of darkness,” has shone in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ.
Here, the statement "to give the light of the knowledge of the glory of God" does not have to be taken to mean that this is done non-evidentially. In the immediate context he is talking about Jews who reject the new revelation of God in Christ. He is saying that Christians, in contrast, ahve hadh the light of God shine in them and have accepted Christ. This could occur by way of the Holy Spirit helping to remove their irrational rejection of the evidence, for instance. Even the staunchest of evidentialists will pray for people that God will enlighten their hearts, and draw them to Himself. There is no reason to treat this as in conflict with the evidence.
It is also important to bear in mind that Paul was teaching a new revelation of God. He has new information -- that Jesus is the Jewish Messiah, God manifest in human flesh, etc. Paul has been travelling around the Mediterranean proclaiming this message, and some are accepting and others rejecting. It is thus quite reasonable for him to see this as God shining His light upon them.
Finally, let me say a brief word about Romans 8:16, which states that “The Spirit himself bears witness with our spirit that we are children of God.” This is a text often used in support of reformed epistemology, which maintains that the internal witness of the Holy Spirit is veridical in itself, and that one does not need any public evidence in order to have a rational confidence in Christianity’s truth. However, this verse is speaking about assurance of salvation in the context of people who already believe the truth of Christianity. Such assurance is not going to help anyone who has doubts about Christianity's truth at all. The previous verse (verse 15) states,
For you did not receive the spirit of slavery to fall back into fear, but you have received the Spirit of adoption as sons, by whom we cry, “Abba! Father!”
The text thus implies that this is the work of the spirit within us. Therefore, it appears to be referring to our desire for a relationship with God, moved by the Spirit, as evidence that we are reconciled with God.