Actually, there are very few contemporary accounts from independent (i.e. non-Christian) sources that mention him. Mostly, independent sources refer to the "cult" of the Christians and the like, rather than to a historical Jesus. Nevertheless, it seems plausible that there was a real person around whom the various myths of Christianity coalesced. It is debateable as to how much of the content of the gospels and the other New Testament writing record actual sayings or doings of the man himself, compared to how many things are merely attributed to him by the writers. As gmilam said, scholars generally agree that the Mark gospel is the primary source for some of the content in Matthew and Luke. John is a later writing. The situation we're in is kind of like people who, a thousand years from now, find fragments of fan fiction that all refer to a person called Harry Potter, which they then choose to compile into a definitive textbook. Those future scholars note that many of the texts agree on certain common elements: the Potter character can do magic, he has two close associates named Ron and Hermoine, his nemesis is a figure whose name is variously given as "the Dark Lord" or "Voldemort" or "He Who Must Not Be Named" (there is some debate, but most scholars agree that these all seem to refer to the same person), etc. For some reason, whatever the primary source was, it has been lost to history. No doubt, some of those future scholars would argue, like you, that due to the consistency of a number of different text fragments, it is very likely that the accounts of this "Harry Potter" person are "most likely close to right", even though there is not total consistency in all the recovered source fragments. Some might conclude that, 1000 years ago, the "magic" referred to in many fragments might have been real. Even if they were to discount that as too improbable, they might surmise that the "Harry Potter" figure was a real person, or at least based largely on a real person. See the problem? The same argument could be made for the Harry Potter fan fiction fragments recovered from the rubble of World War III.