Evidence for the life of Jesus is not just found in the Gospels. He was mentioned by a variety of non-Christian writers in the years following his death.
1. Josephus, a first century Jewish historian, mentions Jesus twice in Jewish Antiquities. The first time he mentions Christ is when he writes about the condemnation of James “the brother of Jesus the so-called Christ."
Later he writes, “At this time there was a wise man who was called Jesus. And his conduct was good and he was known to be virtuous. And many people from among the Jews and from the other nations became his disciples. Pilate condemned him to be crucified and to die. And those who became his disciples did not abandon his discipleship. They reported that he had appeared to them three days after his crucifixion and that he was alive.”  Some of this quote may be an interpolation by a later Christian editor but the fact that a Jewish historian mentions Jesus at all is significant.
2. The Roman historian Tacitus wrote in 115 A.D about the fire that destroyed Rome in A.D. 64, “Nero fastened the guilt ... 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 Pilatus, and a most mischievous superstition, thus checked for the moment, again broke out not only in Judaea, the first source of the evil, but even in Rome....”
3. Pliny the Younger wrote to Emperor Trajan around A.D. 112 seeking advice concerning the prosecution of Christians in the court of law. Concerning Christians, he writes, “they were in the habit of meeting on a certain fixed day before it was light, when they sang in alternate verses a hymn to Christ, as to a god, and bound themselves by a solemn oath, not to any wicked deeds, but never to commit any fraud, theft or adultery, never to falsify their word, nor deny a trust when they should be called upon to deliver it up; after which it was their custom to separate, and then reassemble to partake of food – but food of an ordinary and innocent kind.”
4. The Babylonian Talmud mentions Jesus in a negative light. In writings dated to A.D. 70-200, they say, “On the eve of the Passover Yeshu was hanged. For forty days before the execution took place, a herald ... cried, "He is going forth to be stoned because he has practiced sorcery and enticed Israel to apostasy."
5. Lucian of Samosata, a second century Greek satirist, wrote about the Christians, “The Christians ... worship a man to this day – the distinguished personage who introduced their novel rites, and was crucified on that account.... [It] was impressed on them by their original lawgiver that they are all brothers, from the moment that they are converted, and deny the gods of Greece, and worship the crucified sage, and live after his laws.”
 Josephus, Antiquities xx. 200
 Josephus, Antiquities 18.63-64
 Tacitus, Annals 15.44
 Pliny, Epistles x. 96
 The Babylonian Talmud, transl. by I. Epstein (London: Soncino, 1935), vol. III, Sanhedrin 43a, 281
 Lucian, "The Death of Peregrine", 11-13, in The Works of Lucian of Samosata, transl. by H.W. Fowler and F.G. Fowler, 4 vols. (Oxford: Clarendon, 1949), vol. 4