"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 patronising 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, p55 (Wikipedia paste)
The name for this is the "Liar, Lunatic, or Lord" trilemma. I would add a fourth for completeness, which is "legend"---the possibility that the disciples made up the story.
I'm going to start addressing these piece by piece.
Lunatic(Edit)
If He was mistaken in His claim that He was God born as a man, then how did he achieve the miraculous things he did? I admit that a trickster could fake a healing, but how could a delusional person do the same?
Legend(Edit)
Ancient history is an odd thing, but the evidence for the testimonies we have of Jesus are some of the most secure of the old stuff we know. I read someone ranting that the account of Jesus has had 2000 years to change. Nope. We have very early copies of texts that match what we have today, so at the most you could claim that there were a few generations between Jesus and the text we have now.
Lord(Edit)
Yes.
Romans 3:23 - for all have sinned and fall short of the glory of God,
Romans 6:23 - For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord.
Romans 10:9-10 - because, if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. 10 For with the heart one believes and is justified, and with the mouth one confesses and is saved.
Revelation 3:16 - Behold, I stand at the door and knock. If anyone hears my voice and opens the door, I will come in to him and eat with him, and he with me.