Trilemma - lord, liar or lunatic?
The 'Trilemma'
One of the arguments Lewis uses in his books has grown particularly famous. It is referred to as the 'trilemma' or the 'lord, liar or lunatic' problem, and it is a response to people who believe Jesus was a great human teacher but was not really divine.
Look at Jesus's words as recorded in the Bible, Lewis said: he claimed to be the Son of God and to have the power to forgive sins. They are not the sort of claims a good human being would make.
A man who was merely a man and said the sort of things Jesus said would not be a great moral teacher. He would either be a lunatic - on the level with a man who says he is a poached egg - or he would be the devil of hell. You must take your choice. Either this was, and is, the Son of God, or else a madman or something worse. You can shut Him up for a fool or you can fall at His feet and call Him Lord and God. But let us not come with any patronising nonsense about His being a great human teacher. He has not left that open to us. He did not intend to.C.S. Lewis, Mere Christianity
The passage displays Lewis's overall attitude towards his faith: he felt Christianity was an all-or-nothing affair. Half-heartedness was not to be tolerated. There was no middle ground.