C.S. Lewis's trilemma is an argument intended to prove the divinity of Jesus. C. S. Lewis was an Oxford medieval historian, popular writer, and Christian apologist. He used the trilemma argument in a series of BBC radio talks later published as the book Mere Christianity. It is sometimes summarized either as "Lunatic, Liar, or Lord", or as "Mad, Bad, or God".
... A frequent criticism is the claim that the statements and actions referred to by Lewis were an invention of the early Christian movement, seeking to glorify Jesus. According to Bart Ehrman, 'there could be a fourth option – legend'. Lewis himself denied the accounts of Jesus were legends: "I have read a great deal of legend and I am quite clear that they are not the same sort of thing". N. T. Wright, a leading New Testament scholar, comments that Lewis's argument "doesn't work as history, and it backfires dangerously when historical critics question his reading of the Gospels."
There are sufficient non-Christian and Christian writings that dismiss the idea that Jesus was simply a "legend" and not a real person that existed when he was said to. The issue really is what does one "do" with Jesus?
I had an semi-atheistic (agnostic?) friend that didn't deny Jesus was a real person he just dismissed the resurrection account. He believed that Jesus wasn't really dead and that he revived in the tomb and walked out of his own strength. When I offered the rebuttal that the Romans were masters of execution and would have ensured Jesus WAS dead before they took him down from the cross, that he was wrapped in burial cloths that included about a hundred pounds of spices - (John 19:39 - the substitute for embalming back then), that there was a bunch of Roman soldiers guarding the tomb - and who, under threat of death, would not have neglected their duty to make sure Jesus stayed in the tomb - and that some of those guards conspired with the chief priests to explain how the tomb came to be empty, and, finally, how every Apostle but one died a martyr's death rather than denounce that Jesus was the risen Messiah (many people die for a lie, but no one dies for what they KNOW is a lie). All these points may have cracked a little of his skepticism but he refused to accept that Jesus really did rise from the dead. I believe the chief cause of this is pride and, of all the sins man is guilty of, this is the one the Lord hates the most. We can certainly see why Jesus said that the "poor in spirit" will be blessed and will see heaven. Being poor in spirit requires humility - an acknowledgment that we have nothing of our own works of righteousness or merit to earn salvation but must trust wholly in the grace of God who saves us through faith.