Oct 20, 2009
Sorry, I should have been a bit clearer.
The Sunni belief about Imam Mahdi is that he will be a normal person who will be born and grow up and then receive revelation from Allah that he is the Imam of the age, the Imam Mahdi.
This differs from "12'er" shia beliefs that the Imam Mahdi will be/is the 12th Imam who will return. It also differs from other Shia sects' views on the identity of the Imam Mahdi.
The differences between sects is over the identity of the Imam Mahdi, not that whether he will come or not. There is little difference over what his actions/mission will be when he comes, although there is some debate over whether the prophecies will be fulfilled literally or metaphorically.
Cheers,
Shafique