In the book Mere Christianity, Lewis famously proposed that Jesus' status as a great moral teacher cannot be divorced from his claims to divinity:
"I am trying here to prevent anyone saying the really foolish thing that people often say about him: I'm ready to accept Jesus as a great moral teacher, but I don't accept his claim to be God. That is the one thing we must not say. 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 the man who says he is a poached egg - or else he would be the Devil of Hell. You must make your choice. Either this man was, and is, the Son of God, or else a madman or something worse. You can shut him up for a fool, you can spit at him and kill him as a demon and 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."
According to the argument, most people are willing to accept Jesus Christ as a great moral teacher, but the Gospels record that Jesus made many claims to divinity, either explicitly ("I and the father are one." - John 10:30) or implicitly, by assuming authority only God could have ("...the Son of Man has authority on earth to forgive sins..." - Matthew 9:6). Assuming that the Gospels are accurate, Lewis said there are three options:
1. Jesus was telling falsehoods and knew it, and so he was a liar.
2. Jesus was telling falsehoods but believed he was telling the truth, and so he was insane.
3. Jesus was telling the truth, and so he was divine.
Lewis held that for Jesus to be a liar or insane would contradict his position as a "great moral teacher", and the remaining option would make Jesus both a "great moral teacher" and divine. This was aimed against a specific line of reasoning which accepts the Jesus portrayed in the gospels as a "great moral teacher", but not as a divine being. Lewis maintained that they are failing to deal with the logical consequences of their position.