Reasons to Believe

Lewis’s Mere Christianity Relevant Today

C. S. Lewis’s death was overshadowed by the enormous press coverage of the same-day shocking assassination of President John F. Kennedy. Yet Lewis’s legacy endures and his popularity continues to grow as many of his distinctive ideas continue to resonate among believers.

Lewis’s Enduring Idea of Mere Christianity

One such idea, found in the preface of Lewis’s book by the same name, introduces his idea of “mere Christianity.” This term refers to a group of essential and “agreed, or common, or central”1 Christian doctrines (such as the Trinity, the Incarnation, and the Atonement) that all branches of historic Christendom affirm.

Lewis describes historic Christendom as being like a large house with many individual rooms. The branches of Christendom (Eastern Orthodox, Roman Catholic, Protestant) as well as individual denominations within Protestantism (Lutheran, Reformed, Anglican, Baptist, etc.) live in their own various rooms. Lewis suggested that mere Christianity (the essential shared doctrines reflected in the historic creeds of Christendom) represents the hallways or corridors that connect all the individual rooms.

However, Lewis insists that people live and churches function within the rooms themselves, not in the hallways. In other words, individual believers cannot live as mere Christians but rather must embrace a fuller version (a denomination or branch) of the faith. He states: “I hope no reader will suppose that ‘mere’ Christianity is here put forward as an alternative to the creeds of the existing communions.”2

Not all members of Christendom find Lewis’s idea of mere Christianity acceptable. For example, at least some Roman Catholic theologians do not accept the idea that the Catholic Church is merely one room (or one denomination) among many.3 Rather, for traditional Catholicism the Catholic room is the historic Christian church.

While mere Christianity isn’t a perfect description of Christendom, nevertheless many Protestants see significant value in it.4 For example, sometimes all genuine Christians, regardless of their denominational connections, need to stand together. These hallway interactions give believers an opportunity to show unity. Additionally, the hallways offer a venue for allowing individual denominations to share their unique theological features with members of other denominations.

Lewis also makes two critical points about unity and charity. Concerning the need for Christian unity in an unbelieving world, he states:

Our divisions should never be discussed except in the presence of those who have already come to believe that there is one God and that Jesus Christ is His only Son.5

And of the need for Christians to treat each other charitably, he states:

When you have reached your own room, be kind to those who have chosen different doors and to those who are still in the hall.6

Though Lewis has been dead for fifty years, his work—even just the content found in the preface of his amazing book Mere Christianity—contains ample wisdom that today’s Christians can’t afford to miss.

Subjects: Historical Apologetics, Historical Theology

Kenneth R. Samples

I believe deeply that “all truth is God’s truth.” As an RTB scholar I have a great passion to help people understand and see the truth and relevance of Christianity’s truth-claims. Read more about Kenneth Samples.

1. C. S. Lewis, Mere Christianity (New York: Simon & Schuster, 1996), 8.

2. Ibid., 11.

3. See David Mills, “No Mere Christianity,” First Things, October 18, 2010,

4. See Michael S. Horton, “Whose Orthodoxy?” Modern Reformation 17 (September/October 2008): 14–19,

5. Lewis, Mere Christianity, 6.

6. Ibid., 12.