Dr. Dan Nessett

Dr. Nessett is a retired computer scientist now residing in Billings, Montana, where he teaches a course on logic to high school homeschoolers at Mt. Olive Lutheran Church.

You will hear people say that Christianity and reason are opposed to one another, or at least that Christianity owes no allegiance to reason. This stems from a misunderstanding. Reason is simply the application of logic to understanding. It’s what we use to make sense of things. There are three main logical systems.

The first is inductive logic. Inductive logic attempts to formulate a causal model from empirical data. This is the logic used in science. For example, you observe the sun rising in the east in the morning. The sun continues to rise in the east every morning. You conclude that every morning the sun will rise in the east. The second is deductive logic. This formulates an inference from a premise or set of premises, arriving at a conclusion. The formulation specifies that if the premises are true, then the conclusion must also be true. The third, less commonly known system, is abductive logic. Abductive logic attempts to determine the cause of some effect. It is used extensively in medical diagnoses, legal trials, and archeology. Think Sherlock Holmes or Columbo.

The Reformation established (perhaps more accurately, reestablished) the principle of sola Scriptura. We assert that all Christian doctrine is based on the teachings of Holy Scripture, which is the inerrant, infallible Word of God. This is a prime example of deductive logic. The premises supporting any doctrinal statement are found in God’s Word and the doctrinal statement (the conclusion) follows deductively from those premises. For example, the word “Trinity” does not exist in the Bible. The teaching that God is three in one and one in three arises from the consideration of various passages (e.g., Romans 1:7, John 20:28, Acts 5:3-4, Deut. 6:4-5, Matt 28:18-20, John 10:30, 1 Cor. 15:24, John 15:26, among others) that together give the conclusion or teaching of the Trinity.

Not only do we use deductive logic in order to formulate various Christian doctrines, the Holy Spirit often uses deductive logic in His teaching. For example, in Matt. 12:9-12, Jesus says, “Which one of you who has a sheep, if it falls into a pit on the Sabbath, will not take hold of it and lift it out? Of how much more value is a man than a sheep! So, it is lawful to do good on the Sabbath” (ESV). While this is stated as a question, the sense is “If a sheep falls into a pit on the Sabbath, you will take hold of it and lift it out. You consider it lawful, because it is a good thing to do. Therefore, you agree that it is lawful to do good on the Sabbath.” Here Jesus uses deductive logic to defend his miracles of healing on the Sabbath.

This deductive reasoning (the key to recognizing deductive logic is the use of “if…then”, where many times “then” is implied) is found also in 1 Cor. 15:13, “But if there is no resurrection of the dead, then not even Christ has been raised” (ESV). You can find similar examples in John 8:39ff, 1 Cor. 15:12-16, 2 Chron. 7:14, Mark 11:25, John 15:6- 10, and John 14:23. So, while the Bible is God’s own Word and not an academic treatise built on a foundation of logic, it certainly uses deductive logic, thereby affirming the legitimacy of using logic in deciding and defending doctrinal statements.

Why, then, do some feel reason is opposed to Christianity? This occurs due to a misunderstanding of what exactly reason is. This misunderstanding, which is common, has its roots in the Enlightenment.

Roughly speaking, the Enlightenment was the era in which the educated classes decided that the determination of theological truth did not depend on God’s Word. While the Bible was not completely discarded, it became only one of many sources, which included the evidence of the senses, empiricism, ancient Greek philosophy, and scholarly speculation. Enlightenment thinkers baptized this new approach to epistemology as “Reason.” This new idea of “Reason” conflicted with the old concept in which reason acknowledged the authority of Scripture and served Scripture. It discarded the belief that God’s Word comprises the facts (the premises) and substituted a new system in which you seek truth by considering all the possible ways in which potential effects might be justified. Put plainly, deductive logic was replaced by abductive logic. Enlightenment thinkers presupposed that some principle (i.e. effect) was correct—e.g., there were no miracles—and then looked for causal support wherever they could find it.

Immediately prior to the Enlightenment, Europe was wracked by religious conflict, especially the Thirty Years War. It is estimated that 4.5 to 8 million soldiers and civilians died during this war. The governing elites turned against intellectual and theological disagreements of any kind, and this led to prejudices that warped their thinking when deciding what was true and what was false.

For example, Anthony Collins, a British free-thinker and Enlightenment philosopher, proposed that revelation (i.e., the Bible), should conform to man’s natural idea of God. Thomas Jefferson, in his Jefferson Bible, eliminated every mention of miracles, the visitation of angels, and the resurrection of Jesus. Instead, he emphasized moral principles that he extracted from the New Testament text. In summary, Enlightenment philosophers eviscerated the principle that the Bible was the inerrant, infallible Word of God.

So, Enlightenment scholars imposed restrictions on what evidence they considered legitimate when looking for solutions to intellectual problems. If the Bible supported positions that these scholars found offensive, they simply ignored God’s Word and sought answers from other sources: empirical science, ancient Greek philosophy, etc. This is the forensic approach used by abductive logic. But it is an illegitimate application of abductive logic. It should attempt to explain observed facts by identifying the most likely cause. Enlightenment philosophers instead manufactured principles derived from their intellectual biases and then attempted to justify them by finding causes that were products of their imagination. This is not reason; it is sophistry. It rejects the certainty of God’s revelation, replacing it with unsubstantiated speculation.

So, the term “Reason” became shorthand for the intellectual approach formulated in the Enlightenment. This is what many Christian theologians mean when they say Christian doctrine and “Reason” are antithetical. The Enlightenment definition of “Reason” is incompatible with the principle of sola Scriptura. It elevates the mind of man over the revelation of God. But sound logical thinking, true reason, is a legitimate and necessary tool God has given us to understand His Word.


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