I added a recommendation of this essay to my discussion so I am updating it to today.
From p. 224 of Davis, Kendall and O'Collins' book "The Incarnation." (Oxford University Press, 2002). The essay is entitled "Was Jesus Mad, Bad, or God."
I highly recommend Davis's essay. He presents evidence based on the passages that even the Jesus Seminar is willing to accept as genuine and argues, based on those, that Jesus is making implicit deity claims.
1. Jesus claimed either explicitly or implicitly, to be divine.
2. Jesus was either right or wrong in claiming to be divine.
3. If Jesus was wrong in claiming to be divine, then Jesus was either mad or bad.
4. Jesus was not bad.
5. Jesus was not mad.
6. Therefore Jesus was not wrong in claiming to be divine.
7. Therefore Jesus was right in claiming to be divine.
8. Therefore, Jesus was divine.
An interesting issue that I think no one to my knowledge has talked about. Of course the argument didn't originate with Lewis, it is the theme of Chesterton's The Everlasting Man. And Lewis refers to the argument by its Latin title, aut deus aut homo malus, in many of his letters. Now if you think about it, if an argument has a Latin name, you'd think its goes way way back. So where did it come from. It looks like an argument tailor-made for the Arian controversy, and I recall reading something in Lewis that suggests that it was used in Athanasius' "On the Incarnation," which as we know, his friend Sister Penelope translated and he wrote the introduction for. Does anyone know this argument's history?