Merely Christian
Merely Christian
Though his parents were Irish Protestants, when Lewis converted later in life he joined the Church of England. He aimed to reach as many people as possible with his apologetic books, which meant that he was anxious to avoid points of disagreement between the different Christian denominations and focus on the ideas they all agreed on: the core of Christianity.
That was what Lewis did when he gave the radio talks that were later published in book form as Mere Christianity. He sent part of the text to clergymen of the Church of England, the Roman Catholic Church, Methodist and Presbyterian denominations to make sure his representation of 'mere Christianity' was one that they could all agree on.
He did not intend 'mere Christianity' to be an alternative to the other denominations:
It is more like a hall out of which doors open into several rooms. If I can bring anyone into that hall I shall have done what I attempted. But it is in the rooms, not in the hall, that there are fires and chairs and meals. The hall is a place to wait in, a place from which to try the various doors, not a place to live in.C.S. Lewis, in the introduction to the reprint of Mere Christianity
Analogy
The hallway illustration is only one example of Lewis's penchant for analogy. He broke down complicated questions for an audience with little or no religious knowledge.
In a memorable example, when explaining the meaning of 'numinous' Lewis asked the reader to suppose they had been told there was a tiger in the next room: "you would probably feel fear". If, however, they believed there was a ghost in the next room, they would feel "fear, but of a different kind ... with the Uncanny one has reached the fringes of the Numinous". (The Problem of Pain)
In facing quite a complicated question about the idea that God lives outside time, Lewis used another clever analogy:
Suppose I am writing a novel. I write "Mary laid down her work; next moment came a knock at the door!" For Mary who has to live in the imaginary time of my story there is no interval between putting down her work and hearing the knock. But I, who am Mary's maker, do not live in that imaginary time at all. Between writing the first half of that sentence and the second, I might sit down for three hours and think steadily about Mary ... and the hours I spent in doing so would not appear in Mary's time (the time inside the story) at all.C.S. Lewis, Mere Christianity
Piano keys, playwrights, megaphones and horses: Lewis recruited all these and more to explain his points. They are one of the chief factors in his lively and accessible writing style.