There are plenty of theories around that Muhammad and Christ did not exist.
Whether they did or not exist is not a problem to me.(an agnostic)
In the case of Muhammed the problem is what Muslims believe , and not what you or I believe or what is true or not true.
Islam is a fatal religious belief for us Infidels, when Muslim believers are willing to kill us and die for their beliefs.
Christianity is not a fatal threat to others if you don't stay in the religion or join it, if the New Testament and the 10 commandments are followed.
The only threat Christianity poses is it is no match for Islam in its naive be nice to others belief system that Muslims will take advantage of, and are doing that right now -Tom
Capt. Tom wrote: "... the problem is what Muslims believe..."Again, while I believe you and I are on the same page with regards to concern about Islam, my interest in it's beginnings persists.
As for their beliefs, they too are subject to interpretation as well...
"...historic sites lost include the Prophet’s birthplace – now a library – and the house of his first wife, Khadijah, which was replaced with a public toilet block..."