There are many Christians today who argue that logic is unnecessary, useless, or unimportant. According to them, we should spend our time on bigger and better things, like reaching people for Jesus. Some in our churches would argue that we should not waste our time studying logic, but instead, we should study the Word of God more. Some even piously claim that “logic is not the gospel, so what’s the point?”
Many churchgoers engulf themselves in irrational thought and dismiss logic altogether. This kind of thinking is certainly present, if not predominant, in churches today, and it expresses a deep lack of understanding of what logic is and why it is necessary. Perhaps this negative view of logic stems in part from the deeply rooted anti-intellectualism of many evangelical Christians who seek an emotional high in their religious experience rather than a deeper rational understanding of the Word of God. This can be seen in most of the Charismatic churches that downplay the importance of doctrine and do not concern themselves with testing their experiences in light of God’s Word (1 Thess. 5:21, 2 Tim. 3:16).[i] However, any attempt to disparage logic is self-refuting for the very reason that one must use logic in order to make their own argument against logic intelligible. Thus any attack on logic is undermined by the antagonist’s own use of it. This is simply unavoidable.
Many who desire to throw logic out the window in pursuit of other “nobler” endeavors do not realize that logic is foundational to all disciplines, all thought, and all language. Those who would argue that we should study our Bibles instead of wasting our time with logic commit the fallacy of a false dilemma and miss the fact that the correct method of Biblical interpretation, that is to interpret Scripture in light of Scripture, requires the most fundamental law of logic, which is the law of non-contradiction. Those who would argue that logic is not the gospel do not understand that affirming and proclaiming the gospel requires the laws of logic, such as the law of the excluded middle (A is either B or non-B). The law of the excluded middle states that a proposition or statement is either true or false and a person must affirm in their own thinking that the gospel is either true or false before they can proclaim it as true. If logic is required for the affirmation and proclamation of these most basic–indeed all–Christian truths, then every Christian should understand logic and know how to use it.
What is Logic?
A study in logic may be difficult at first but even the most basic understanding will prove beneficial. For this, we might consider the nature of a logical fallacy as an introduction to logic. A fallacy is a mistake in reasoning. All logical fallacies violate the rules of logical inference in one way or another. In order for a person to reason correctly and think rationally, he must think logically. Dr. Gordon Clark stated simply that logic is the “science of necessary inference.”[ii]
Logic, therefore, may be explained as the correct process of reasoning which is based on universally fixed rules of thought. These universally fixed rules of thought are often expressed as the laws of logic. The three fundamental laws of logic are the law of non-contradiction, the law of identity, and the law of the excluded middle. All of these laws are expressed in Scripture, which in turn provides the Christian a firm foundation by which to account for logic. The law of non-contradiction (A is not non–A) is an expression of the eternal character and nature of God, “for he cannot deny [contradict] himself” (2 Tim. 2:13). The law of identity (A is A) is expressed in God’s name, “I AM WHO I AM” (Exodus 3:14), and the law of the excluded middle (A is either B or non-B) is expressed in Christ’s own words, “He who is not with Me is against Me” (Luke 11:23).[iii]
It is precisely because the laws of logic are embedded in Scripture that the Christian is able to establish from an epistemological standpoint that they are fixed and universal laws. Without this epistemological foundation, we cannot account for the laws of logic and it is for that reason that Scripture rather than logic is chosen as the Christian axiom. We agree with Dr. Clark that “Scripture, the written words of the Bible, is the mind of God. What is said in Scripture is God’s thought.”[iv] With this in mind, we now have an epistemological foundation by which we can assert that the laws of logic are fixed and do not change, because “the word of our God will stand forever” (Isa. 40:8). Likewise, we can also assert them as universal laws because “he upholds the universe by the word of his power” (Heb. 1:3).
Although it is true that all rational thinking requires logic, it is impossible to establish an epistemological foundation for logic strictly from the mind of man, for nothing requires man to think logically, and his mind has no universal significance at all. The Christian must understand that logic is not descriptive of human thinking–it is not psychology–but is rather prescriptive for all human thought. This means that logic does not describe how a person does think, but rather how a person should think if they are to think correctly. No laws of logic could ever be derived from a description of how people think because many people tend to think irrationally, illogically, often contradicting each other and even themselves.
The laws of logic can, however, be derived from a description of how God thinks because He is always consistent, rational, logical and never errs in his reasoning. Logic then is, as Dr. Clark wrote, “the characteristic of God’s thinking. It is not subsequent temporally, for God is eternal and there never was a time when God existed without thinking logically.”[v] God cannot lie because it is inconsistent with His eternal character and He will not and cannot contradict Himself. “The Glory of Israel will not lie or change His mind; for He is not a man that He should change his mind” (1 Sam. 15:29). This is just one verse of many that provide us a description of the nature and character of God. This is the way in which God thinks and it is the way in which we ought to think. It would be fallacious, however, for one to derive a prescriptive ought statement from the descriptive is statement of God’s nature and character. Fortunately, the Christian is not merely left with a description of the way in which God thinks but we are also given a prescription for the way in which we ought to think. Scripture tells us, “You, therefore, must be perfect, as your heavenly Father is perfect” (Matt. 5:48). Paul also exhorts us to “be imitators of God, as beloved children,” (Eph. 5:1).
It should be clear by now that the Christian is able to account for the laws of logic from an epistemological foundation that is consistent and rationally justifiable within the Christian worldview.
Our Moral Obligation to Think Logically
It may come as a surprise to many Christians to learn that we have a moral obligation to think logically. Perhaps this is because they have not considered carefully that it is impossible to obey God if our thinking is illogical. We often associate sinful thoughts with the vices of lust or hatred, but the truth is that all sin originates in our thinking. “Although adultery and theft are commonly regarded as overt actions, their origin is in our thinking. Sin is the result of intellectual error.”[vi] Clark was correct then, to point to such verses as Proverbs 23:7–“As a man thinks in his heart, so is he”–in order to point out that “sin is first of all mental and only afterward overt.”[vii]
Some might find this disturbing and may wish to separate logic from morality, but logic is necessary for morality as well because without logic there can be no distinction between deception and truth, good and evil, right and wrong. It is no wonder then that the Scriptures are logically consistent. If this were not the case then we would not be able to discern truth from error. If God’s thinking is logically consistent and the Scriptures are part of the mind of God, then it is impossible to obey scriptural commands if we contradict the Bible in the way we think.
The reality is that we often do not stop to consider just how intellectually disobedient we can be in our thinking. It is important to realize that it is impossible to love God with all our mind if we are illogical. How can we surrender every thought captive to the Lordship of Christ (2 Cor. 10:5) if our thinking does not reflect the logical consistency of Scripture? The inescapable result of failing in this area is compromise, error, and sin. We inevitably begin to adopt worldly and secular thinking which is firmly opposed to the Word of God. We should recognize that every attack from the enemy is an attack on the Word of God. A clear example of this can be seen in the current debates over same-sex marriage and abortion.
Christ asserts that marriage is between a man and a woman (Matt. 19:4-5), so we stand in direct defiance if we insist that same-sex marriage is morally good. When we likewise insist on the rights of women to abort their unborn children then we defy God and advocate the murder of children on the altar of convenience and shame. Those who advocate such positions stand in direct opposition to Christ and His Word. Worse yet, professing Christians who hold such positions display and an incredible amount of logical inconsistency and as a result, have no basis for believing that Jesus died on the cross for their sins. If they do not believe the Bible when it speaks on the issue of marriage, the sin of homosexuality, and the life of an unborn child, then what basis do they have for believing the truth of the cross? How convenient it must be to arbitrarily pick and choose what suits us. Such advocates of logical inconsistency would be hard-pressed to provide a rational reason for believing that the gospel is true while rejecting its source as a lie when it doesn’t suit them.
Can Unbelievers Account for Logic?
The unbeliever cannot account for logic in his own worldview and therefore cannot account for his ability to think rationally. The challenge has been made many times to unbelievers to account for logic in their own worldview and it has always fallen short or gone unanswered. Never has an adequate response been given. In formal debates, the challenge is often ignored by the unbeliever, yet the challenge demands an answer because debates presuppose logic. The unbeliever is required to use logic in order to make his argument against Christianity consistent and intelligible, but only the Christian worldview can account for logic. He is therefore required to rob the Christian worldview in order to make his argument against Christianity intelligible.
Some argue that logic is merely a description of nature. Logic, however, cannot be accounted for in nature because logic concerns thinking and governs how we ought to think. The 18th century Scottish Philosopher David Hume identified the impossibility of deriving an “ought” statement from an “is” statement. Nature can only provide a description of what is but cannot provide a prescription of what ought to be so it cannot tell us how we ought to think. Logic is also immaterial and conceptual while nature is just the opposite. This proves to be an impossible hurdle for the materialistic worldview of atheism to rise above.
Due to the materialist’s inability to account for an immaterial law, many try to adopt a form of rationalism. Rationalism is the theory that all knowledge comes from logic alone, apart from the senses and revelation. The rationalist assumes the laws of logic but ultimately fails to account for them. This is problematic because in order for a worldview to be complete it must be able to account for the laws of logic which are a precondition of intelligibility. Because the Rationalist cuts himself off from divine revelation, he isolates himself in his thinking. He attempts to arrive at knowledge from logic alone but has no epistemological foundation for the universal laws logic because they are not descriptive of his own thinking but rather prescriptive of how he ought to think. If he supposes that all knowledge comes from logic but is unable to provide a foundation of knowledge by which he can know the laws of logic as prescriptive, independent, and invariant laws of thought, then he is hopelessly lost. One cannot navigate from logic alone to any propositional knowledge or truth.
We will further demonstrate the failure of rationalism by attacking its first premise. Rationalism says that all knowledge comes from logic alone but this knowledge claim itself cannot be inferred from logic alone. Although the laws of logic are communicated as propositions which require the laws of logic in order to be intelligible, the laws themselves provide no additional content about reality or truth. The laws of logic can only be applied to how we think. They only tell us how we should think but provide no content of thought. The rationalist must show that the laws of logic provide all of the necessary content of thought and that this content can only be derived from the laws themselves and nothing else. The law of non-contradiction is a universal rule of thought but the law itself cannot tell us what is universal.
If rationalism cannot know its first premise by its own method then it is shown to be self-refuting and fails as a theory of knowledge. No self-contradictory epistemological foundation can account for the law of non-contradiction. If rationalism fails as a theory of knowledge then there is nothing that can be known on rationalism. If one cannot know anything on rationalism then it cannot account for the universal laws of logic which exist outside the mind of the rationalist. We need more than what rationalism can offer. We need divine revelation from God.
Many reject the epistemological foundation of Christianity which accounts for logic in the Word of God and instead turn to Empiricism. This comes as no surprise since the rebellious mind is hostile towards God and rejects that “the fear of the LORD is the beginning of knowledge” (Prov. 1:7).
When 17th-century rationalists saw the shortcomings of assuming logic alone, the world shifted towards empiricism. Today empiricism may be regarded as the most widely held epistemological foundation and it is the underlying basis for many arguments against Christianity. When unbelievers argue that there is no empirical evidence for God they are presupposing the epistemology of empiricism. But it is impossible to even make such an argument intelligible without presupposing the laws of logic. Using logic is necessary for such argumentation but presupposing the truth of empiricism is problematic because logic cannot be accounted for empirically. Empiricism holds that all knowledge comes through the senses but the laws of logic have never been observed by any of the senses since they are conceptual. Even if one were to make an appeal that every perceived contradiction they have ever encountered has been false, they still have no hope whatsoever of asserting the laws of non-contradiction on empiricism. This is, in part, due to the fact that the law is universal but their experience is limited. There simply is no way to establish a universal law by one’s limited experience. Any attempt to do so would be committing the fallacy of induction because the induction could never be completed.
Another aspect of the laws of logic that must be established is the fact that the laws are timeless and fixed. There is simply no way to establish the timeless nature of a law on the basis of one’s own limited past experience and there is no way to empirically verify that the future will reflect the past because the future has not been observed. There is no basis for saying that the law of non-contradiction will stand tomorrow on an empirical foundation. No universal timeless law can ever be empirically verified because no one has experienced all the past or any of the future.
When the empiricist states, “all knowledge comes through the senses” he does not mean that “no knowledge comes through the senses” for that would contradict his claim. He is, therefore, using the law of non-contradiction in order to make his claim intelligible. It is ironic then that logic is necessary to define empiricism and give it meaning yet at the same time it requires that empiricism be regarded as false. The claim that all knowledge comes through the senses requires the application of the law of non-contradiction in order that it might be intelligible and understood yet the claim is self-contradictory. The claim that all knowledge comes through the senses is a knowledge claim that has not been observed by the senses. Empiricism has never been observed and cannot be empirically verified. Not only does empiricism fail to account for logic but the same logic that is necessary for its own definition requires that empiricism itself be rejected by the rational mind.
Many people attempt to combine rationalism with empiricism to overcome the shortcomings of both. Yet rationalism cannot deduce anything from logic alone, ultimately failing to account for logic itself, and empiricism cannot yield any knowledge or propositions from the senses, including the laws of logic. Just as the unbeliever requires air to breathe with which to curse God, so also he requires the laws of logic in order to make his case against God intelligible. Since the Bible alone can properly account for logic the unbeliever is forced steal from the Christian worldview in order to argue against it. This is the inevitable tragedy of every argument raised against the knowledge of Christ. “The fool says in his heart, ‘There is no God’” (Ps. 14:1).
[i] Scripture references are ESV unless otherwise noted. All emphases in Scripture quotations are mine.
[ii] Gordon H. Clark, Logic, Fourth ed. (Unicoi, Tennessee: Trinity Foundation, 2004), 162.
[iii] Scriptural references for the laws of logic are provided in part by W. Gary Crampton’s “The Westminster Confession of Faith and Logic,” The Trinity Review (February, 2014).
[iv] Gordon H. Clark, “God and Logic,” The Trinity Review (November/December, 1980), edited by John W. Robbins, 4.
[v] Clark, “God and Logic,” 3.
[vi] Gordon H. Clark, “The Theologian’s Besetting Sin,” The Trinity Review (March/April, 1992), edited by John W. Robbins.
[vii] Clark, “The Theologian’s Besetting Sin,”