On this day (April 4) in 1945, the last in a famous series of talks by C.S. Lewis was broadcast across the BBC. These talks would become the substance of Mere Christianity, a book often listed as the most influential Christian book of the twentieth century. Lewis was a layman who was trained in philosophy, logic, and literature, not theology. How did he manage to produce such a profound and important work on the Christian faith? 

While many are familiar with the story of Lewis’ conversion from atheism to Christianity, fewer know anything about his spiritual growth after conversion. An early critical element of his formation came in 1935, four years after his conversion, when Lewis was assigned to write the volume on sixteenth century literature for the Oxford History of English Literature. Lewis read everything published in English in the sixteenth century, including every work of Thomas More and the translations of Martin Luther, John Calvin, and all other Catholic and Protestant thinkers of the Reformation.  

From this unmatched education in historical theology, Lewis realized that many of the accusations leveled by each side of the Reformation weren’t wholly true but often caricatures of the other’s positions. This encouraged him to focus, in his BBC addresses, on those points to which all Christians agreed. The label “mere” Christianity was borrowed from seventeenth-century Puritan Richard Baxter. 

Another important element in Lewis’ spiritual growth came in 1940 when he decided he needed a “spiritual director.” In the nearby village of Cowley was Anglican priest Father Walter Adams of the Society of St. John the Evangelist. Lewis met with Father Adams every week for confession and spiritual direction for the next twelve years. 

While very little is known about their meetings, Adams was a High Church Anglican who directed Lewis toward traditional devotional disciplines. Lewis began to pray through the Psalter each month and developed a deep appreciation for the Lord’s Supper. Father Adams pointed him to Richard Meux Benson, the founder of the Society of St. John the Evangelist. Benson’s theology influenced Lewis in profound ways, particularly the ideas found in book four of Mere Christianity. 

Father Adams’ spiritual direction had a profound and dramatic effect on Lewis. For example, Lewis attributed the overcoming of a number of personal sins to prayer and fasting and, according to friends who knew nothing about his meetings with Adams, Lewis’ character began to change in profound ways in the early 1940s. Every book Lewis is known for, aside from Out of the Silent Planet and The Problem of Pain, were written after he began to meet with Father Adams. In fact, the rate at which he produced books grew tremendously after 1940, despite his busy schedule traveling and speaking at Royal Air Force bases during the War, giving the BBC talks that would become Mere Christianity, personally answering every letter he received, and carrying out his duties at Oxford University. 

Of course, Lewis was gifted with an incredible mind, an amazing education, and an ability to write. Still, he recognized his need for a mentor. His spiritual formation included a deep devotional life and serious, in-depth study, each anchored firmly in the historic Christian tradition. The breadth and depth of Lewis’ theological readings made him, as a self-taught theologian, one of the great Christian thinkers of the twentieth century, and his practice of spiritual disciplines, worship, and spiritual accountability shaped his heart. With head and heart in line, God granted Lewis an extraordinary ministry. 

In this way, Lewis is a model of discipleship, the kind that provides a foundation by which we can serve others and live a life pleasing to God.