Lol that most CEMBers still believe that Mo believed his own stories.
I think you misunderstand what I mean when I say "Believed his own lies".
It is a common trait of people who have personality disorders. It is very common for people to do this, this is especially true of people who are pathological and narcissistic.
Without going to in depth with it, imagine like this:
A kid playing may pretend to be a superhero. The child will invent superpowers and stories of their super hero exploits, and treat them like they are real, so as to not spoil the play.
I did this (and am sure others here have to) as a child, and can remember it. I remember completely believing the nonsense I had been making up. Like when I was 5 and convinced myself I was a cyborg, or when I was 9 and was terrified of a ghost that was haunting my house....that I had completely made up. Things like these both made life more interesting and inflated my own ego ("I'm so cool because I'm a robot").
The more these are indulged the more important they get, and kids will make up any number of lies to continue them. Now, I dont only mean lies to other people, but more importantly to themselves. Cognitive Dissonance is the main factor here. If you wish to maintain the ego boost/self importance of being a robot, you need to believe it too...else the cognitive dissonance.
All children do this in play to certain degrees, and most grow out of it.
Now, someone with say some form of personality disorder may have this to an extreme degree, and not grow out of it in adulthood in the way children.
So imagine an adult who plays make believe like an overly imaginative child...and that gives you an idea. There are many many examples, from the cult leaders who drink their own cool aid to Kings who really believe they are gods to people who cry over tragedies that never happened
EDIT:
OF COURSE....for the sake of this we are assuming that Muhammed did exist, and as a historical character was a 'prophet' who recited the quran