there are ancient, non-Christian documents supporting the besides the Gospels that supported the Gospels. For example, Josephus, a Jewish historian from the first century, also wrote about Jesus, such as in the following passage called the Testimonium Flavianum:
About this time there lived Jesus, a wise man, if indeed one ought to call him a man. For he was one who wrought surprising feats and was a teacher of such people as accept the truth gladly. He won over many Jews and many of the Greeks. He was the Christ. When Pilate, upon hearing him accused by men of the highest standing among us, had condemned him to be crucified, those who had in the first place come to love him did not give up their affection for him. On the third day he appeared to them restored to life, for the prophets of God had prophesied these and countless other marvelous things about him. And the tribe of Christians, so called after him, has still to this day not disappeared (qtd. in Christ 103-104).
While most scholars agree that the phrases 'if indeed one ought to call him a man,' 'He was the Christ,' and 'On the third day he appeared to them restored to life' were inserted by early Christians, the rest is accepted as written by Josephus and plays an important part in buttressing the Gospels as a corroboration by a non-Christian.
There is also an extremely important piece by the Roman historian Tacticus, which helps confirm another basic premise in the Gospels.
Nero fastened the guilt and inflicted the most exquisite tortures on a class hated for their abominations, called Christians by the populace. Christus, from whom the name had its origin, suffered the extreme penalty during the reign of Tiberius at the hands of one of our procurators, Pontius Pilate, and a most mischievous superstition, thus checked for the moment, again broke out in Judea, the first source of the evil, but even in Rome. Accordingly, an arrest was first made of all who pleaded guilty: then, upon their information, an immense multitude was convicted, not so much of the crime of firing the city, as of the hatred of mankind (quoted in Christ 107-108).
Not only does this state that Nero persecuted Christians for the fire that he started in Rome, but it also confirms the crucifixion story.