True, on Arabic coins and inscriptions, and in papyri and other documentary evidence in the language, Mohammed only appears in the 680s, some fifty years after his death (whatever its exact date). This is the ground on which some, notably Yehuda D Nevo and Judith Koren, have questioned his existence. But few would accept the implied premise that history has to be reconstructed on the sole basis of documentary evidence (i.e. information which has not been handed down from one generation to the next, but rather been inscribed on stone or metal or dug up from the ground and thus preserved in its original form). The evidence that a prophet was active among the Arabs in the early decades of the 7th century, on the eve of the Arab conquest of the middle east, must be said to be exceptionally good.
Everything else about Mohammed is more uncertain, but we can still say a fair amount with reasonable assurance. Most importantly, we can be reasonably sure that the Qur'an is a collection of utterances that he made in the belief that they had been revealed to him by God. The book may not preserve all the messages he claimed to have received, and he is not responsible for the arrangement in which we have them. They were collected after his death – how long after is controversial. But that he uttered all or most of them is difficult to doubt. Those who deny the existence of an Arabian prophet dispute it, of course, but it causes too many problems with later evidence, and indeed with the Qur'an itself, for the attempt to be persuasive.
