Why don’t they teach logic at these schools?”
At one point in the classic book
The Lion, the Witch and the Wardrobe by C.S. Lewis, an exasperated professor utters the words, “Logic! Why don’t they teach logic at these schools?” C.S. Lewis,
The Lion, the Witch and the Wardrobe (Harper Trophy, 2000), p. 48.Lewis not only believed in truth, but also in our ability to use logic as an aid in determining truth.
Although it is true that logic studied as a formal discipline can lead to challenging formulas and diagrams, in a basic sense we all use it regularly. In reading this article, for example, you are using logic to interpret the words you see. Without logic, you could not make sense of this sentence. Interpreting a rational sentence requires a rational mind with the ability to comprehend words that are structured in a way that makes sense — in short, words that are organized logically.
Historically, Aristotle was the first to explore logic as a formal discipline, but he did not invent it. The underlying principles of logic are readily discernible. We use them every day to get through some of the simplest decisions and actions in life.
Logicians generally offer four broad principles or laws of logic.
First, the
law of identity makes the obvious observation that something is itself and, therefore, cannot be something else (A is A).
Second, the
law of non-contradiction deals with the concept of antithesis and states that something cannot be true and not true at the same time and in the same sense (A is not non-A).
Third, the
law of excluded middle is often presented as “either A or non-A.” For instance, God either exists or He does not exist.
Fourth, the
law of bivalence assesses propositions as either being true or false. “God exists” is either a true or a false statement. Space does not allow a thorough analysis of logic or its foundations. For a general introduction to the topic see
Come, Let Us Reason: An Introduction to Logical Thinking by Norman Geisler and Ronald Brooks (Baker, 1990) and the standard textbook on the subject,
Introduction to Logic by Irving Copi and Carl Cohen (Prentice Hall, 2004). Copi and Cohen, incidentally, define logic as “the study of the methods and principles used to distinguish good (correct) from bad (incorrect) reasoning” (p. 3, eighth edition).
Furthermore, the Bible is not against logic. In fact, biblical Christianity encourages the use of the mind. In Isaiah 1:18 (NIV) we read, “‘Come now, let us reason together,’ says the LORD.” In the New Testament Jesus is clear that we are to love God — not only with all our heart, soul, and strength, but also with our
mind (Matthew 22:37; Mark 12:30; Luke 10:27).
Christians are also called to defend the truth by appealing to reason and evidence (Acts 26:25; 1 Peter 3:15). Acts 1:3, for example, says Jesus “gave many convincing proofs” as evidence for His resurrection. In Acts 26:25-26, after the Apostle Paul gives his testimony and outlines the gospel message, he is accused of being insane. Paul replies: “What I am saying is true and reasonable. The king is familiar with these things, and I can speak freely to him. I am convinced that none of this has escaped his notice, because it was not done in a corner.”
In Acts 26, Paul uses logic to make his case for Christianity. He appeals to his own experiential testimony (noting how he used to persecute Christians), makes mention of the resurrection of Christ, and implies that many are aware of the events surrounding the gospel of Christ. Logically, Paul believes the Christian message because of the evidence, both experiential (his encounter with Christ) and evidential (the case for the resurrection, for instance, and the testimony of witnesses).
First Peter 3:15 also appeals to logic: “Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have.” The Greek word translated as “answer” is
apologia and was used in reference to giving a legal defense. In this passage, Peter calls readers “to give the reason for the hope that you have.” Reasons presuppose the validity of reason and logic.
The appeal in Acts 1:3 to “many convincing proofs” again relates to logic because a reasonable appeal is made to the evidence for the resurrection. In other words, Luke, the author of Acts, is not asking for blind faith, but faith founded on logical inferences. The New Testament records that many people saw Christ after his death, that Christ proved he was raised bodily by eating food and by inviting doubting Thomas to touch him (John 21:12-13; Luke 24:38-43). These are all logical appeals to evidence and reason.
As a former atheist, C.S. Lewis was well aware of the role that reason played in his conversion to Christianity. That’s why he offered reasonable, logical arguments in support of his beliefs. In doing so, Lewis often utilized what is known as
abductive reasoning. Abductive reasoning is similar to reasoning used by the scientific community in that it uses reasonable evidence to come to the best explanation.
In making his case for Christianity, Lewis used abductive reasoning to argue that the Christian explanation of reality — the Christian worldview — is more reasonable and probable than the alternatives.
C.S. Lewis used abductive reasoning to argue that the Christian explanation of reality — the Christian worldview — is more reasonable and probable than the alternatives. (Recall that abductive reasoning is similar to reasoning used by scientists in that it uses reasonable evidence to come to the best explanation.)
Now I’ll take a closer look at two of Lewis’ key arguments that use abductive reasoning:
- The argument from Christ
- The argument from longing
God or a Poached Egg?
Jesus once asked his disciples, “Who do people say I am?” After hearing a few replies, he put forth a more pointed and personal question: “‘But what about you?’ he asked. ‘Who do you say I am?'” (Mark 8:27-29).
In exploring the alternatives regarding the claims of Christ, Lewis used abductive reasoning to conclude that the most probable explanation is that Jesus is who He said He was. In
Mere Christianity, Lewis provides a brief presentation of his argument: “I’m trying here to prevent anyone saying the really foolish thing that people often say about Him: ‘I’m ready to accept Jesus as a great moral teacher, but I don’t accept His claim to be God.’ That is the one thing we must not say. A man who was merely a man and said the sort of things Jesus said would not be a great moral teacher. He would either be a lunatic — on the level with a man who says he is a poached egg — or else he would be the Devil of Hell. You must make your choice. Either this man was, and is, the Son of God: or else a madman or something worse.” C.S. Lewis,
Mere Christianity (Macmillan, 1960), pp. 55-56. Lewis also explores this issue in some of his other writings such as in “What Are We to Make of Jesus Christ?” in
God in the Dock (Eerdmans, 1970).
Beyond some biblical hints at such reasoning (John 8:48-49 and John 10:33), the core of this argument goes back to Eusebius of Caesarea (c. 263-339), who outlined it in
Demonstratio Evangelica (“Proof of the Gospel”). Lewis popularized the argument in
Mere Christianity. Since then, several apologists have expanded it to include other alternatives beyond the traditional “Lord, Liar, or Lunatic?” options. Contemporary works that address the argument from Christ include
Handbook of Christian Apologetics by Peter Kreeft and Ronald Tacelli (InterVarsity, 1994), “Was Jesus Mad, Bad, or God?” by Stephen T. Davis in
The Incarnation (Oxford, 2002), and
Without a Doubt by Kenneth Samples (Baker, 2004).Based on the evidence and the truth of the Bible, these apologists, like Lewis, conclude that the most reasonable explanation is that Jesus is who He claimed to be.
Longing for “The Real Thing”
Another line of reasoning Lewis used is called the argument from longing or desire. In it, he not only makes the case for God, but also the case for heaven.
Lewis believed that everyone experiences sensations of desire and longing. We may spend a lifetime trying to fulfill these desires by pursuing earthly pleasures such as taking vacations, moving from one sexual partner to another, or trying different hobbies — “always thinking that the latest is ‘The Real Thing’ at last — yet always ending up disappointed.”
Our experience tells us, Lewis continues, that “Creatures are not born with desires unless satisfaction for those desires exists. A baby feels hunger: well, there is such a thing as food. A duckling wants to swim: well, there is such a thing as water. Men feel sexual desire: well, there is such a thing as sex.” C.S. Lewis,
Mere Christianity, p. 119-120.
How, then, can we explain deep inner longings that we have that nothing in this world seems to satisfy? Of course, it would make sense to begin by demonstrating that human beings do indeed have these longings. Some might argue that not everyone does have these desires or that they really do not point to God. Lewis disagreed, though, arguing that our longings for the ‘other’ — even though they may manifest themselves in different ways, such as material pursuits — are really longings for the transcendent joy that is found in God alone. For a thorough presentation and defense of Lewis’ argument from longing see Peter Kreeft’s essay, “C.S. Lewis’s Argument from Desire,” in
G.K. Chesterton and C.S. Lewis: The Riddle of Joy (Eerdmans, 1989), pp. 249-272.
The fact that we have this longing, combined with the fact that nothing on earth can truly satisfy it, led Lewis to this reasonable conclusion: “If I find in myself a desire which no experience in this world can satisfy, the most probable explanation is that I was made for another world.” Ibid, p. 120.
True and Reasonable
In The Lion, the Witch and the Wardrobe, the professor concludes that a little girl named Lucy is telling the truth about her claims to have visited a world called Narnia. He does this by using abductive reasoning. The professor rationally explores the alternative explanations and concludes that they are unlikely. “For the moment then and unless any further evidence turns up,” argues the professor, “we must assume that she is telling the truth.” C.S. Lewis,
The Lion, the Witch and the Wardrobe (Harper Trophy, 2000), p. 48. By the way, the reasoning of the professor presented in this section of the book parallels Lewis’ logic in his argument from Christ.
In making the case for Christianity, we, too, can use logic such as abductive reasoning. If we can provide arguments and evidence that Christianity is more reasonable and probable than other explanations of reality, then it is rational to conclude — “for the moment and unless any further evidence turns up” — that Christianity is, as the apostle Paul said, “true and reasonable” (Acts 26:25). This does not mean that faith has no value or role in Christian belief, but it does mean that Paul’s faith was founded in a reasonable God, even though His actions might not always appear reasonable from our limited perspective.
