On September 19, 1931, 94 years ago today, three friends had a conversation on Addison’s Walk, a tree-lined path on the grounds of Magdalen (pronounced “Maudlin”) College in Oxford. This discussion would be the catalyst for the conversion of one of the most important Christian thinkers of the twentieth century.

Hugo Dyson and J.R.R. Tolkien, both committed Christians, were discussing Christianity and myth with C.S. Lewis. Lewis was an odd duck. Intellectually, he was a rationalist, but temperamentally, he was a romantic: he loved mythology and fairy tales but saw no real value in them since they did not provide the only kind of truth his rationalist mind could accept. He started as an atheist, but philosophical reflections had forced him to accept the existence of God in 1929, describing himself as the most dejected and reluctant convert in all England. But this was just a conversion to theism, not Christianity.

Two years later, after dinner on September 19, Dyson, Tolkien, and Lewis went to Addison’s Walk and began a discussion on metaphor and myth, “interrupted,” as Lewis reported in a letter to Arthur Greaves, “by a rush of wind which came so suddenly on the still, warm evening and sent so many leaves pattering down that we thought it was raining.” The conversation then turned to Christianity. Lewis accepted the historicity of the Gospels but could not accept the idea that Jesus’ crucifixion could in any way save us.

Tolkien and Dyson pointed to myth as a way of explaining Jesus’ death and resurrection, but Lewis dismissed myth as “lies breathed through silver”—as beautiful as the myths were, they were not true as Lewis the rationalist understood truth. Dyson and Lewis countered that the pagan myths were true in the sense that they were inklings of what God himself would do in history. As Lewis would describe it later, they were the good dreams of the pagans, or in Tolkien’s words, fragments of splintered light, pieces of truth not completely understood but pointing to the fulness of truth expressed in Christ. The Gospel, they said, was a myth like the myths of Baldr and the other dying and rising gods that Lewis loved so much, but with one tremendous difference: it really happened. It was myth made fact.

The three returned to Lewis’s room at Magdalen and the conversation continued long into the wee hours of the morning—Tolkien left at around 3 AM and Dyson around 4.

This conversation was the key to Lewis’s conversion. It provided a means to unite his mind and heart around the Gospel, to connect what he loved with what he saw as truth. He would later use this in a new, imaginative approach to apologetics and theology that led the University of St. Andrews to award him an honorary Doctor of Divinity.

The conversation on Addison’s Walk also helped Lewis develop his theories of myth and led him to embrace fairy tales as a method of communicating truth. Without it, we would never have had Narnia, the Ransom Trilogy, the Great Divorce, or Till We Have Faces. Even more, we might not have had C.S. Lewis the Christian at all.