C.S. Lewis on the Godhead of Christ

I've just been involved in a discussion on FishEaters Forum regarding a woman hoping to convert her Jewish husband, whose major problem is the Holy Trinity. Here is her original post, slightly edited for clarity,

Please help. My Jewish husband told me today that the only obstacle to his conversion is the Trinity. He believes there is one God and has a lot of trouble being convinced that Jesus is God and the Holy Spirit is God. 

In fact he cites Jesus’s last words on the cross “my God why has Thou forsaken me” as proof that Jesus was just a man who died… like Moses. A great prophet but nothing more than that. 

He really does object to praying to three beings.  

Here is my answer, taking as my cue his belief that Christ was 'A great prophet but nothing more than that.'

That is one thing he CANNOT be. If he's not God, he's either insane or the Father of Lies, Satan himself. There can be absolutely NO doubt that he said he is God. 'God said to Moses: I AM WHO AM. He said: Thus shalt thou say to the children of Israel: HE WHO IS, hath sent me to you' (Exodus 3:14). 'Jesus said to them: Amen, amen I say to you, before Abraham was made, I am' (St John 8:58). Verse 59 continues, 'They took up stones, therefore, to cast at him', because they knew that he had just claimed to be God, which to them was blasphemy worthy of being stoned to death.  

As C.S. Lewis said on the question,

Quote: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 or you can fall at his feet and call him Lord and God, but let us not come with any patronizing nonsense about his being a great human teacher. He has not left that open to us. He did not intend to. ... Now it seems to me obvious that He was neither a lunatic nor a fiend: and consequently, however strange or terrifying or unlikely it may seem, I have to accept the view that He was and is God. (Lewis, C. S., Mere Christianity, London: Collins, 1952, pp. 54–56. In all editions, this is Bk. II, Ch. 3, "The Shocking Alternative.")