[alancarp]

That Mohammed never actually existed. He is a made-up character developed in response to Jesus Christ and Christianity.

[Verginius Rufus]

How do you explain the Arab conquests in the 7th century if Mohammed never existed?

There are people who claim that Jesus never existed, that he was invented by Josephus. Equally nuts.

[zeke37]

You are absolutely right. He is a composite character of several people. Most likely, he never existed. His name is actually a title: Machmad or Machmed means lovely one from Song of Solomon 5: 16.