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Mere Christianity | Main Ideas


The Trilemma

In one of the book's most famous passages, C.S. Lewis uses unforgettable language to present a very old argument for the divinity of Jesus. This argument is often referred to as the "liar, lunatic, Lord" trilemma because of its assertion there are only three ways to interpret Jesus's claims to divinity. Either Jesus is what he says he is, he is insane, or he is lying. In Book 2, Chapter 3 Lewis addresses the commonly held notion that Jesus was merely a great moral teacher and nothing more. It is foolish, Lewis says, to make this assertion. If Jesus was just an ordinary wise man, he would not have made the claims he did. Rather, "he would either be a lunatic ... or else he would be the Devil of Hell."

Jesus, a Jew, was speaking to the Jewish community, which was suffering under Roman oppression. His claims—of forgiving sins, of having eternal existence, of "coming to judge the world at the end of time"—were not those an ordinary Jewish man would have made. If Jesus and his audience had been pantheists who believed God was not separate from any part of the created world, there would be nothing particularly extraordinary about these claims. But Lewis explains that Jesus was speaking in the context of Judaism. This religion is emphatically monotheistic and emphasizes a strict demarcation between God and man. A Jew who said such things would not have meant them as metaphors or general truths applicable to everyone.

Therefore, Lewis concludes, if we refuse to take Jesus's claims at face value, there remain only two ways of evaluating them. Either they are the words of an insane man or the deliberate deceptions of an evil man.

The Law of Human Nature

In Book 1 Lewis argues the existence of what he variously refers to as the Law of Human Nature or the Moral Law. This universal, inborn law exists within each person. It attempts to compel the person to do what is right rather than what is wrong. The Law works because there is a basic moral standard of right and wrong that is universal across cultures and across eras. All people know this Law without having to be taught. It is universally recognized that stealing is wrong, for example—although there may be disagreement about what constitutes stealing. This Law was not made by humans, but we all experience it telling us what we ought to do.

The Law of Human Nature differs from all the other laws that govern the universe, like the laws of gravity and thermodynamics. These scientific laws only describe what happens, not what ought to happen. Conversely, the Law of Human Nature does not describe what happens but what ought to happen. Humans can choose to break the Law of Human Nature, whereas a rock cannot choose to disobey the law of gravity. In fact we all break the Law of Human Nature by failing to do what we know we ought to do. The Law remains, however, governing every aspect of our lives, despite our failure to comply with it.

The Law of Human Nature is obviously real, Lewis maintains, yet it has nothing to do with observable facts. "Electrons and molecules behave in a certain way, and certain results follow," Lewis states in Book 1, Chapter 3. Unlike the entire nonhuman universe, people behave in a certain way and one "know[s] that they ought to behave differently." Nor is this Law of Human Nature and its accompanying moral standard correlated with any of our instincts, comforts, and preferences. We cannot explain it in terms of anything else we know about the universe. "It begins to look as if ... there is more than one kind of reality," Lewis states.

Lewis states there are two types of explanations for how the universe came to be. Either it is the result of pure chance and chemistry or else there is a "controlling power outside the universe"—God. Science is incapable of determining which is the truth since it can only work with observable facts. However, if we consider the Law of Human Nature, we will see it as evidence of this "controlling power." It attempts to influence us to behave one way and not another, and yet it does not determine the observable facts of our behavior. This controlling power must be similar to a mind because it has preferences and gives instructions.

In other words, the Law of Human Nature is proof the universe was created by God who is good. Moreover, He cares so much that we should behave in a decent, virtuous way that He put a Law inside our heads telling us to do so. Lewis goes on to argue that by our failure to keep this Moral Law we have put ourselves at odds with God. From here Lewis introduces Christianity, whose doctrines are in accord with all Lewis has established by arguing the reality of the Law. It offers a way for people to reconcile themselves with the God who created the Law.

Christian Morality

In Book 3 Lewis discusses the seven Christian virtues that constitute Christian morality: prudence, temperance, justice, fortitude, faith, hope, and charity. Because character is shaped by actions over time and God is concerned with our character, all of our actions have importance. The virtues guide us toward the kind of actions necessary to shape our character in the way God wishes. Through dedication to practicing these virtues, a Christian attains salvation—but not in the way one might expect.

It is not by being perfectly virtuous that we are saved, Lewis claims. In fact it is impossible for us to be completely moral because of our human nature. Nonetheless, Christians must put all their effort into trying to practice these virtues perfectly. But they will quickly realize no matter how hard they try they will fail. After repeated efforts and repeated failures, Christians reach a point where they have two choices. They may fall into despair—or they can surrender.

Surrender means that Christians give up trying to act on their own power and earnestly ask God for help in doing what they cannot do. When the request is made, Christ can then begin to do his work of transforming the flawed human personality into his own perfection. This request is crucial to Christianity since God created humans with free will. The repeated failure is also crucial because it makes Christians humble enough to ask for God's help, and it creates in them the faith that allows them to rely completely on Christ. Paradoxically, Christians can attain moral perfection only by trying to do so and failing.

Three-Part God

A foundational idea in Christianity is the Trinity, which holds there is a single God with three aspects or parts: God the Father, Christ the Son, and the Holy Spirit or Holy Ghost. In Book 4 of Mere Christianity, C.S. Lewis explains the concept of the Trinity in terms of a "three-personal God."

Lewis addresses the confusion about how there could be a God that is one God at the same time He is three Persons by invoking a dimensional metaphor. He asks the reader to consider a cube, which is six squares (two-dimensional objects) at the same time it is one cube (a third-dimension object). "The Christian account of God involves just the same principle," he writes in Book 4, Chapter 2. Our confusion about the Trinity is natural because, being limited in our understanding due to our existence on the "simple and rather empty" level of humans, "we cannot fully conceive a Being" that is three persons as well as one God.

Lewis goes on to argue that truly walking the Christian path means "being actually drawn into that three-personal life" of God. Lewis illustrates his meaning by using the example of a Christian at prayer. "God is the thing to which he is praying" as well as "the thing inside him which is pushing him on" and "the road or bridge along which he is being pushed" (Book 4, Chapter 2).

In Book 4, Chapter 4 Lewis addresses the nature of the relationship between the three persons that are God. The Father aspect of God beget the Son. Beget means the Son was created by the Father and is of the same nature as the Father. The relationship between the Father and the Son, whose nature is love, is so dynamic and powerful it gave rise to the third person, the Holy Spirit. Since God came into existence outside of time, the causal chain of the three persons of Father, Son, and Holy Ghost is not linked to any temporal order. The three persons of God are all eternal.

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