Clive Staples Lewis was the 20th century's most influential Christian apologist, whose Mere Christianity, The Chronicles of Narnia, and The Screwtape Letters brought Christian faith to millions. An Oxford and Cambridge don, Lewis converted from atheism to Christianity partly through conversations with his friend J.R.R. Tolkien.
Lewis argued for Christianity through reason, imagination, and moral intuition. His 'argument from desire' suggested that human longing for transcendence points to a transcendent reality. His BBC radio broadcasts during World War II, later published as Mere Christianity, defended basic Christian beliefs common to all denominations.
The Narnia series clothed Christian themes in fantasy for children. The Screwtape Letters offered satirical instruction in temptation. Lewis's science fiction (Space Trilogy) and works like The Problem of Pain and A Grief Observed (on his wife's death) addressed suffering. Though not a systematic theologian, Lewis communicated Christian faith with clarity and imagination that continues to convert skeptics and strengthen believers.