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Last Updated on July 9, 2015, by eNotes Editorial. Word Count: 858

To understand Mere Christianity, one of C. S. Lewis’s most well-known apologetics, one must understand his audience. The work is a compilation of talks on Christian philosophy that Lewis gave to radio listeners between 1941 and 1944. Lewis is an accomplished scholar, but he is writing for a popular audience. Therefore, he leaves out a great deal of material that scholars would look for in a systematic theology; most notably, epistemology. The book takes for granted a commonsense attitude toward morality, reason, and the Bible. Many scholars criticize the book for oversimplifying some issues, but Lewis’s arguments are sound if one understands his views on literary criticism, history, and Socratic logic as expressed in his other works.

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The title comes from Lewis’s claim to abstract from the various denominations a kind of “pure” Christianity. Like a Puritan, Lewis believes that this “undiluted” Christianity would be as potent as merum, undiluted wine. However, like a Catholic, he relies heavily on tradition and dogmatism.

The book is divided into four main parts, titled after the separate series on which they were based, aired by the British Broadcasting Corporation (BBC).

In “Right and Wrong as a Clue to the Meaning of the Universe,” Lewis discusses commonsense morality. Even young children are aware of right and wrong, and there are some acts that most people recognize as evil. People engage in acts of self-sacrifice that defy pragmatic or utilitarian ethic. Lewis argues that all human beings share a basic moral law. Using Platonic reasoning, Lewis contends that such a moral law requires the existence of a moral lawgiver.

In “What Christians Believe,” Lewis works through the basic concepts of divinity, in a manner similar to what Saint Augustine does in De civitate Dei (413-427; The City of God, 1610). A moral lawgiver must be extrinsic to the universe, eliminating pantheism as an option. Polytheism fails to meet the standard, as pagan gods are capricious and have a supreme God that rules them. Lewis discards dualism since an absolute good and an absolute evil would cancel each other out, and one must be stronger than the other for there to be a moral law. Of all major religious models, Lewis argues, only monotheism supports a definitive moral law.

Lewis then offers the Hebrew Scriptures as the best historical source of a divine lawgiver revealing himself to human beings. Similarly, the canonical Gospels are the best historical texts about the life of Jesus Christ, and these books claim that Jesus is God. Jesus is the only great moral teacher to claim to be God incarnate. Therefore, Lewis challenges the “quest for the historical Jesus” with his famous “trilemma”: Jesus is a lunatic, a fraud, or God, but he is not a “good moral teacher.” Some accuse Lewis of a false dilemma, arguing that the Gospels may have misrepresented Jesus. However, Lewis holds that it is intellectually dishonest to accept some parts of a text as reliable and reject others. A text must be taken as a whole.

J. R. R. Tolkien once remarked to Lewis that Christ is the only historical occurrence of a “grain god.” Lewis builds on that kernel to contend that Christianity is the fulfillment not only of Judaism but also of all pagan religions.

In “Christian Behaviour,” Lewis covers the basic points of Christian ethics. His ethics are mainly Aristotelian, built on the concepts that “virtue is the mean” and that virtue is achieved by building good habits.

In the last part, “Beyond Personality,” Lewis delves into Trinitarian theology. Here Lewis turns more speculative than orthodox. He offers thoughts that seem to be more purely his own (or at least Pythagorean) rather than merely echoing Thomas Aquinas or Saint Augustine.

Lewis suggests that there are “dimensions” of personality. In geometry, there is a huge difference between a one-dimensional line, a two-dimensional plane, and a three-dimensional cube. He suggests that something in two dimensions would be able to understand what one dimension is. However, the two-dimensional entity cannot truly comprehend three dimensions, except by a metaphor (for example, a cube is six squares).

Lewis sees something similar in the Christian understanding of God as “three persons.” He compares animals to one dimension, humans to two dimensions, and God to three dimensions. Animals understand only instinct and interact with humans as if we were similarly instinctual. They are incapable of comprehending our level of rationality. Humans, however, can understand animals, but we are incapable of really understanding the level of existence enjoyed by God. God is so beyond our level of existence that humans cannot really understand his “dimension.” Christ became human to help humans understand God better. The best way for humans to comprehend God’s level of existence is to speak of God as three persons, just as the square might speak of the cube as six squares.

Ultimately, Lewis contends that the goal of Christianity is for the person, with Christ’s help, to expand “beyond personality,” to reach toward the level of existence enjoyed by God. This is achieved by allowing the Holy Spirit to guide the person’s actions and by using Christ as model and mediator.

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