We previously covered the Münchhausen trilemma: an argument that knowledge is impossible because it can never be ultimately justified. Any (true) belief must be based on a good reason in order to be considered knowledge. But the reason is only good if it also is based on a good reason, which is based on a good reason and so on. Now this chain of reasoning either goes on forever, or it doesn’t. If it goes on forever, then human beings could know nothing since finite beings cannot know an infinite number of things. We could never complete the proof of anything, and an incomplete proof doesn’t prove anything.
So it seems that the chain of reasoning must terminate in a good reason that is foundational to all others. But how is this reason itself justified? It cannot be proved from a more foundational reason, otherwise it wouldn’t be the foundation (and we would simply ask the same question of the “more foundational reason.”) Some people suppose that the foundational reason is intuitively self-evident. But not everyone agrees on what this ultimate reason is. Is it sensory experience, rationality, self? Apparently, it is not so self-evident. Furthermore, many things that seem intuitively self-evident (e.g. “the earth is stationary”) are later found to be false. Intuition isn’t a good reason to believe something.
Other people might suppose that we simply cannot prove the ultimate standard, but we accept it anyway as an unprovable axiom. The problem here is that we would literally have no good reason to accept such an ultimate standard. We would have no way of knowing if it is really true since it is unjustified. And since all other beliefs are ultimately based on this standard, their truth is based on its truth, which is unknown. In that case, we could know nothing. We could have beliefs, and perhaps many of them would be true; but they could not ultimately be justified and therefore would not be knowledge. The position that our ultimate standard is unprovable (but perhaps intuitive/obvious) is called foundationalism. It leads inexorably to the conclusion that we cannot know anything. But we do know things. So the solution must lie elsewhere.
The third option of Münchhausen trilemma seems problematic as well. This is the position that the ultimate standard proves itself. So the reason for the ultimate standard is, in some sense, the ultimate standard. But if the ultimate standard is based on itself, does this not commit the fallacy of begging the question? For a standard to prove itself seems like circular reasoning, which is generally considered fallacious – an error in reasoning.
I am going to suggest that God as revealed in Scripture is the ultimate standard for knowledge (Proverbs 1:7). Hence, all truth claims can only be justified if God’s Word is true. As such, God’s Word must somehow justify itself. There is a degree of circular reasoning here, but is such reasoning fallacious? Of course, it is also the case that any competitor to the Christian worldview must also attempt to justify itself. Unbelievers often criticize believers for claiming that the Bible justifies itself, while they unwittingly appeal to their ultimate standard (naturalism, strict empiricism, etc.) as justifying itself. Any alleged ultimate standard must justify itself, otherwise either (1) it wouldn’t be ultimate, or (2) it wouldn’t be justified and we would have literally no reason to believe it.
Most people have learned that circular reasoning is fallacious – a mistake in reasoning. And indeed, it usually is. Unfortunately, few people have reflected adequately upon why circular reasoning is faulty, and if there are any exceptions where it is legitimate. So a brief refresher on logical reasoning is in order.
To be logical is to think correctly – to draw reliable inferences or conclusions from accepted facts. There are two intellectual sins that derail correct reasoning. These are arbitrariness and inconsistency. To be arbitrary is to not have a good reason for a belief. If you don’t have a good reason to believe something, then it may very well be false. So it would be illogical to accept it as true. Inconsistency is when two or more things do not go well together, such as two contradictory statements which cannot both be true at the same time in the same sense. It would be illogical to believe both a statement and its negation (opposite), since they cannot both be true.
An argument is a conclusion based on one or more accepted statements that are called premises. A good argument has true premises and the conclusion follows from them. When the conclusion follows logically from the premises, the argument is valid. A fallacy is a common error in reasoning. Most fallacies make an argument invalid – meaning the conclusion does not follow from the premises. But circular reasoning is different. Circular reasoning is actually valid.
When conclusion B follows logically from premise A, the argument is valid – by definition. And when conclusion A follows logically from premise B, the argument is valid. It is perfectly consistent. Why then is circular reasoning considered a fallacy? The reason is that it is arbitrary. If the only reason to believe B is A, and the only reason to believe A is B, then both A and B might be wrong. In which case, neither is justified. We call such fallacious reasoning a vicious circle.
Virtuous and Vicious Circles
But what if the circle were not arbitrary? Consider how we might prove that laws of logic exist:
(1) Obviously, if there were no laws of logic, then we could not make any arguments.
(2) But we can make arguments.
(3) Therefore, laws of logic must exist.
This seems like a good argument. The premises are true, and the conclusion follows logically from them. So it is valid. Yet, this argument is subtly circular. Why? This argument has a structure referred to as modus tollens. Modus tollens is a law of logic. So this argument uses a law of logic in order to prove that laws of logic exist. It assumes the very thing it attempts to prove, which is circular. And yet, it is not arbitrary.
Immanuel Kant argued that it is reasonable to believe in something if you would have to assume that thing in order to argue against it. That is, to make a logical argument that laws of logic do not exist, we would have to use laws of logic – in which case they do exist. Hence, laws of logic exist.
We cannot prove that laws of logic exist without using them, and hence there will be some degree of circularity. But it is not arbitrary. Rather, it is necessary because proofs require logic. So there is no violation of the principles of reasoning. The argument is self-consistent and non-arbitrary. We might call this a virtuous circular argument.
The Theology of Virtuous Circular Reasoning
Biblical oaths are much like the way beliefs are justified. People would swear by something greater than themselves as the standard that guaranteed that they would do what was promised. Hebrews 6:16 states, “For men swear by one greater than themselves, and with them an oath given as confirmation is an end of every dispute.” And God is the ultimate standard for any oath since there is nothing greater. Hence people swear to God when they mean to make the greatest promise possible. So then what standard does God use when He declares an oath?
Hebrews 6:13 states, “For when God made the promise to Abraham, since He could swear by no one greater, He swore by Himself.” Yes, the standard by which God swears is God. God uses circular reasoning. But it is non-arbitrary. God has a very good reason to swear by Himself, and this reason is explicitly stated in Hebrews 6:13. Namely, there is no one greater by which to swear. That is a good, non-arbitrary reason. Hence, it is a virtuous circle, not a vicious one.
In fact, all of God’s reasoning is necessarily circular. God is all-knowing. So, whenever God draws a conclusion from premises, the conclusion is something that God already knows. Truth is that which corresponds to the mind of God. And the justification for that truth is… that it corresponds to the mind of God. This is not arbitrary, but logically necessary since God’s mind determines all truth. Those people who argue that all forms of circular reasoning are fallacious are in the unenviable position of implying that God’s reasoning is fallacious.
Example: Sensory Experience
To discern a virtuous circle from a vicious one, we need to ask if the circle is logically necessary (non-arbitrary) and self-consistent. Is it justified after the fact? We will find that only the consistent Christian can justify those things necessary for knowledge within his worldview without begging the question. Consider sensory experience. Everyone believes that his or her sensory experiences are basically reliable – that what we see, hear, taste, touch, and smell is a good representation of reality. But is this belief knowledge? What is its justification?
Unbelievers will usually attempt to justify sensory experience by appealing arbitrarily to sensory experience. In other words, they would argue that they know their sensory organs are basically reliable because they have worked well in past experience. But how do they evaluate whether or not their senses worked well in the past? They use their senses to evaluate this. Their eyes and ears have informed them that their eyes and ears are reliable. But this is totally arbitrary. It arbitrarily assumes the reliability of sensory experience as the sole basis for the reliability of sensory experience.
On the other hand, the Christian appeals to Scripture as the ultimate justification for sensory experience. The Bible states that God designed our eyes and ears (Proverbs 20:12). And God expects us to draw correct conclusions about the physical world based on sensory experience (e.g. Luke 7:22, John 3:11). So in the Christian worldview, we have a good, self-consistent reason to believe in the basic reliability of sensory experience.
Yet, this answer has a degree of circularity. Namely, we must use our senses in order to read in the Bible that our senses were designed by God. Does this mean that the reliability of sensory experience is more foundational than the Scriptures? Not at all. This is another example of a difference in the order of chronological discovery and logical primacy. That is, we believe in the reliability of our senses before we discover the logical justification for that belief (the biblical worldview). This is always the case with our most foundational presuppositions. They must be assumed before they are proved.
Yet, after assuming that our senses are reliable, we discover that we have a good independent reason to believe this: the Bible. The circle is not vicious because our belief in reliable senses is not arbitrary; it is rationally necessary for us to discover that it has independent, self-consistent justification. Namely, we need reliable senses to discover what the Bible says about our senses. But when we read the Scriptures, we find that our belief was justified.
Contrast this with the evolution worldview in which human sensory organs are unplanned, non-designed, “accidents” of nature. Evolutionists do believe that their sensory organs are basically reliable. But since they reject the biblical worldview, they cannot ultimately justify that belief within their professed worldview. The only reason they can verbally articulate for their belief in reliable senses is to appeal to reliable senses, which is arbitrary.
And no, it won’t do to say that senses must be reliable because this would have survival value. Grass does perfectly well in terms of surviving, yet it does not have reliable senses. How could an evolutionist know – on his own professed worldview – that he is not a blade of grass? How could he know that his sensory experiences are in fact nothing more than the byproduct of photosynthesis? After all, photosynthesis does have survival value. But this does not guarantee that sensory experience is reliable.
Both Christians and non-Christians believe that their senses are basically reliable. This belief is consistent with the Christian worldview. But it cannot be ultimately justified in any other.
Example: Rationality of the Mind
How do we know that our mind is capable of rational thinking? An unbeliever will generally appeal to instances in which his mental reasoning was correct. But what is he using to evaluate the correctness of those instances? He is using his mind. But this is the very thing we are asking him to justify. He has arbitrarily assumed the rationality of his mind as the sole basis for the rationality of his mind – a vicious circle.
In the evolutionary worldview, humans are simply an unplanned, chemical accident. So by what reason does an evolutionist conclude that his thoughts are any more rational than any other chemical reaction? You would not look to the bubbles in a bottle of Coke to decide what is true. So why look to the human brain if it too is just chemistry?
On the other hand, the Christian has a great reason to trust that the human mind is capable of rational thought; humans are made in the image of God (Genesis 1:26-27). God’s mind is perfectly rational since His thinking determines truth (John 17:17). And God has revealed some of His thoughts to us, such that we can think – in a limited way – God’s thoughts. God calls us to reason (Isaiah 1:18, Psalm 32:9) and to think in a way that is consistent with His nature (Isaiah 55:7-8). In the Christian worldview, it makes sense that our mind would have the capacity to be rational.
Of course, we have not escaped circularity. After all, we must use our mind to understand the Scriptures. But this is not arbitrary. It is necessary and self-consistent, and therefore virtuous. Even someone who denies the Bible will attempt to use his mind to reason; but his confidence in his own mind is inconsistent with his professed worldview. The rationality of the mind is consistent and justified within the Christian worldview. But it doesn’t make sense in any other.
Professed Worldviews and Knowledge
Of course, we use our mind and sensory experiences to know things about the world. Therefore, if our mind and sensory organs were not justified – if we had no good reason to believe in them – then all our other beliefs which depend on these would also be unjustified. We would not really know anything at all. This confirms Proverbs 1:7. Knowledge begins with God.
If any worldview other than Christianity were true, then we couldn’t have knowledge of anything. We might have beliefs, and some of them might even be true. But they could never be justified. We could never know that they are true because we could never provide an ultimate reason for any belief. But, of course, human beings do know things. Therefore, it must be the case that the Christian worldview is true.
Some people mischaracterize the approach by saying that presuppositionalists claim that unbelievers have a problem with knowledge – that unbelievers can never justify their beliefs. This is not correct. God has revealed Himself to everyone. So unbelievers can indeed have knowledge. And their knowledge is justified in exactly the same way as the believer’s knowledge – by revelation from God. The Bible is true whether the unbeliever will profess it or not.
The problem with the unbeliever is not that he cannot justify any of his beliefs. Rather, the problem is that he cannot justify any of his beliefs within his professed worldview. If evolution were true, then knowledge would be impossible. But evolution is not true. Since the Bible is true, evolutionists are able to have knowledge. Their beliefs in sensory experience and rationality are ultimately justified because the Bible is true.
Consequently, the fact that unbelievers do have knowledge demonstrates the truth of Christian worldview. Furthermore, it shows that they do know God. Apart from the biblical God, it would make no sense to trust in sensory experience or the rationality of the mind. When unbelievers accept these truths, it exposes their suppressed knowledge of God in a spectacular confirmation of Romans 1:18-25.
So, the proof of the Bible isn’t a vicious circle such as “The Bible is God’s Word because it says it is.” Rather, the proof is that the Bible says it is God’s Word and makes knowledge possible. This is something the Bible itself indicates (Proverbs 1:7, Colossians 2:3). The Bible proves itself and is the only basis for proving anything else. It’s not a simple (vicious) circle, but a spiral that goes beyond itself and justifies our other beliefs. The proof of the Bible is the impossibility of the contrary. If the Bible were not true, we couldn’t prove that anything is true.
 Otherwise, the Bible would be unjustified; and since all other truth claims depend on the truth of the Bible, they too would be unjustified and we could know nothing.
 Modus tollens has the following form:
If p then q.
Therefore, not p.
 The qualification “basically” reliable is necessary because our senses can be occasionally fooled, as with an optical illusion. But these are the exceptions, not the rule. Furthermore, God gave us multiple senses so that they can corroborate each other, and an error in one can be discovered by another. We also note that because of sin and its curse, some people have damaged or non-functional sensory organs. But again, these are uncommon, and God has given us multiple senses to compensate for the loss of any one.