Mere Christianity | Study Guide

C.S. Lewis

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Mere Christianity | Book 3, Chapter 12 : Christian Behavior (Faith) | Summary



Lewis begins the chapter by pointing out how some parts of Christianity can be immediately grasped by non-Christians, but understanding of other parts only comes after time and effort spent attempting to practice Christian doctrine. Lewis notes the higher sense of faith, which he discusses in this chapter, may be hard to grasp for those who are not dedicated to the Christian path, but he urges his audience to concern themselves only with the parts of Christian doctrine that seem to make sense.

Lewis says that God wants us to be "creatures related to Himself in a certain way." We can't discover this way of being until we have realized we are "bankrupt" with respect to God. Our failure to practice morality perfectly after earnest effort will at some point lead to the moment where we give up our solitary efforts and ask God to accomplish what we cannot. This moment of surrender may happen suddenly or gradually. We "leave it to God" by putting perfect trust in Christ's claim that he will make us sons of God in the same way as Him. We trust Christ will deliver, even though we are bankrupt, and Christ's offer, "everything for nothing," is of inestimable value. Leaving it to God does not mean we stop making an effort. Rather, we redirect our efforts toward "trying to do all that He says." We can now put forth our most sincere effort without anxiety because we know we are progressing toward heaven.

There is a longstanding debate in Christianity regarding whether salvation is attained through faith, through acts, or through both. Lewis claims faith and acts feed each other, forming a single, self-reinforcing cycle. To elevate one while discounting the other is to prevent the attainment of either.

The Bible instructs Christians, "Work out your own salvation with fear and trembling ... 'For it is God who worketh in you.'" Our actions lead us to fail, and our failure leads us to a state of "fear and trembling" as we realize what we really are in relation to God. "The only thing to save [us] from despair at that point" is our faith in Christ. But a person does not work with God like two people work together, for God is within and without us. The path of Christian morality ends with the transcendence of morality. When goodness is absolute, morality has no meaning. Walking this path affords us "a glimpse of a country where they do not talk of those things, except perhaps as a joke."


Lewis emphasizes the inseparability of faith and acts. He is addressing an issue that appeared at the core of Christianity during its earliest days and that underlay the rupture of the Church into Protestant and Catholic in the beginning of the 16th century. It continues to divide Christians to this day. The source of the contention is the doctrine of justification.

It is helpful to think of justification as cleansing, or as the process of replacing injustice with justice. A Christian is justified when God's grace cleanses him of sin and guilt, restoring him to a state of righteousness before God. The question is whether justification depends on an individual's faith, moral actions, or both. St. Paul, one of the primary authors of the New Testament, claimed justification was possible only through the grace of God as transmitted through the resurrection of Christ. It cannot be achieved, Paul said, by keeping the commandments or by good acts.

The concept of justification became a key doctrine in the early Catholic Church when St. Augustine (354–430), whose thought is also foundational to Christianity, held justification to be a gift of God, which cannot be attained by any human effort. The doctrine of justification was expanded in the Middle Ages. The medieval church viewed justification as a joint effort between God and man. This belief paved the way for the rising power of the papacy to secure its power via the institution of a system of indulgences. These indulgences, granted by the papacy, signified God's forgiveness of some part of an individual's burden of sin. The forgiveness moved the Christian toward justification when his faith and good acts fell short. Indulgences were offered as incentives to encourage people to sign up to fight the papal wars of conquest known as the Crusades. They could be bought through donations to the Church—a practice Lewis alludes to in this chapter—and eventually were offered by local governments in exchange for the largest part of a farmer's crop. It is this corrupt system of "salvation for sale" that the theologian Martin Luther attacked in 1517, sparking the Protestant Reformation. After meditating on a passage in the book of Romans, Luther had an epiphany that would change not only his life but also set the tone for the Protestant Church. He proclaimed justification occurred sola fide, Latin for "by faith alone." This doctrine, as well as doctrine of sola scriptura, "by scripture alone," was a radical break with the complexities and hierarchical power structure of the Church. The Roman Catholic Church solidified its opposing position on justification as the result of numerous factors on the part of God and man during the mid-16th century Council of Trent. Four hundred years later, Christianity remains split by the simple question of faith versus acts—what Luther called "the summary of all Christian doctrine."

Lewis avoids taking sides with either Catholicism or Protestantism but issues a jab at both by claiming the truth of justification lies in between the "two parodies of the truth." The whole argument is silly, he says, because faith and works feed each other; they are two aspects of a single cycle. To deny either is to fail at both.

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