"Transposition" was preached in the chapel of Mansfield College, Oxford, on the Feast of Pentecost, May 28, 1944. The day after, a local newspaper, The Daily Telegraph, called Lewis "Modern Oxford's Newman." It was reported that Lewis was so overcome by emotion that he stopped in the middle of the sermon, said "I'm sorry," and left the pulpit. After receiving assistance, and after a hymn was sung, Lewis returned and finished the sermon with his deeply personal feelings about his subject (and its setting) still evident.

Someone has suggested that "Transposition" represents some of C. S. Lewis' best theological thinking. It was really a sermon about spirituality, and the objections that the materialistic thinking (Freudian and naturalistic) of Lewis' day had against it. Many non-believers and "religious pessimists" had protested that the spiritual life of the Christian was a mirage, a psychological projection. To answer this objection Lewis developed a theory called transposition, which meant for him an "adaptation of a richer to a poorer medium."

He explained this to his audience by suggesting that the Christian looks at so-called spiritual events "from above" -- that is, with a godly and "heavenly" viewpoint. The non-believer sees events without God in mind. For Lewis, the Christian's devotion to God, however it is expressed, is not merely a "desire for Heaven" or desire for immortality - it has been placed in us by God.

Since "Transposition" was preached on the day that many Christians celebrated the coming of the Holy Spirit, Lewis used the example of glossolalia, or speaking in tongues, to make one of his major points. He admitted this event was difficult for him to understand, as it was (and still is) for a great percentage of Christians. But he defended this instance of glossolalia (in Acts) because -- although it was for him "an extreme example" of spirituality - he believed it needed defending because of what was at stake. Lewis thought the existence of the spiritual life (as a whole) was under attack by the "mind of the age." "Transposition" was his attempt to articulate his defense of the spiritual life, which he believed with all his heart and mind to be straight from the love of God.

"A Slip of the Tongue" was the last sermon Lewis preached. It was given at the invitation of the Chaplain of Magdalene College, Cambridge, in the college chapel (at Evensong) on January 29, 1956. About a year earlier Lewis had accepted a position at the college as Professor of Medieval and Renaissance Literature. The chapel register reported that the little chapel was so crowded with people (over 100) that extra seats had to be brought in. This sermon was first published in Screwtape Proposes a Toast and Other Pieces (1965). He was helping his publisher plan this volume just before he died.

Lewis started this sermon like he did so many, by identifying with his listeners. When a layman like himself was asked to preach, he told them, the most likely way he could be entertaining and useful would be if he started where he was. Thus the sermon would be like comparing notes with the audience. "A Slip of the Tongue" is a very short and intimate sermon, especially when compared to his other university talks.