First we have the New Testament documents which were written within 75 years of His ministry. There are numerous copies from within 100 years of these being written and thousands of copies. But how do we know the disciples were recording the truth? First the way the stories are written they are not in the form a myth because they are written as eye witness accounts with numerous details that are not central to the man events. Also, since they were written shortly after His death and Resurrection, if it were all a lie, there would have been many who would have protested. Instead, many feared this movement because of the truth of the events that took place and tried to persecute those who spread the stories and teachings.
But there is much more evidence from non biblical historical documents written by Jews and Romans who were not sympathetic to the Christians. One such evidence is the writing of Jewish historian Josephus who lived in Rome during the first century. He wrote one book around AD 94 that refers to Jesus. Here is what he wrote:
Now there was about this time, Jesus a wise man, if it be lawful to call him a man, for he was a doer of wonderful works, a teacher of such men as receive the truth with pleasure. He drew over to him both many of the Jews and many of the Gentiles. He was Christ; and when Pilate, as the suggestion of the principal men amongst us, had condemned him to the Cross, those that loved him at the first did not forsake him. For he appeared to them alive again the third day, as the divine prophets had foretold these and ten thousand other wonderful things concerning him; and the tribe of Christians, so named from him, are not extinct to this day.In this same book Josephus also mentions James as the brother of Christ who was tried before a council called by Anaius and turned over to the authorities to be stoned.
Another account is found in the writing of a Roman historian Tacitus discussing how Emperor Nero accused the Christians being responsible of the burning of Rome:
Hence to suppress the rumor, [Nero] falsely charged with the guilt and punished with the most exquisite tortures, the persons commonly called Christians, who were hated for their enormities. Christos, the founder of the name, was put to death by Pontius Pilate, procurator of Judea in the reign of Tiberius: but the pernicious superstition, repressed for a time broke out again, not only through Judea, where the mischief originated, but through the city of Rome also.There is also Lucian of Samosata who wrote a satire, The death of Peregrines, that was popular in its day. He wrote:
The Christians, you know, worship a man to this day––the distinguished personage who introduced their novel rites, and was crucified on that account.... These misguided creatures start with the general conviction that they are immortal for all time, which explains the contempt of death and voluntary self-devotion which are so common among them; and then 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. All this they take quite on faith, with the result that they despise all worldly goods alike, regarding them merely as common property.Also we have another Roman historian Suetonius who wrote Life of Caudius. In this book he wrote: "As the Jews were making constant disturbances at the instigation of Chrestu, [Claudius] expelled them from Rome." The event is also referred to by Luke in Acts as it took place in AD 49. In another book he wrote, The lives of the Caesars, you find this quote: "Punishment by Nero was inflicted on the Christians, a class of men given to a new and mischievous superstition."
Finally we have Pliny the Younger who is also known as Plynius Seconds who was the governor of Bithynia which is a territory in what today is known as Turkey. He was seeking advice from the Roman emperor Trajan on how to deal with the Christians. He wrote the following:
They affirmed, however, that the whole of their guilt, or their error, was that they were in the habit of meeting on a certain fixed day before it was light, when they sang in alternate verse a hymn to Christ as to a god, and bound themselves to a solemn oath, not to any wicked deeds, but never to commit any fraud, theft, adultery, never to falsify their word, not to deny a trust when they should be called upon to deliver it up.He also mentions in this letter that he had been forcing the Christians to "curse Christ, which a genuine Christian cant be induced to do."
We can also find reference in the Jewish Talmud seeing Jesus as a rabbi and claming that he was executed and had disciples being born of a virgin. There are several mentions of him as being an illegitimate bastard son of Miriam.
There is also evidence in the writing of Julius Africanis, who wrote around AD 221. He referred to a writer named Thallus who wrote in AD 52 mentioning a darkness that fell midday when Jesus was crucified. He wrote:
Thallus, in the third book of his histories, explains away this darkness as an eclipse of the sun––unreasonable, as it seems to me (unreasonably, of course, because a solar eclipse could not take place at the time of the full moon, and it was the season of the Paschal full moon that Christ died.)The bottom line is there is no valid basis to deny the historical reality of Jesus Christ. What is recorded in the New Testament is an accurate description of what took place. It has been well documented by the Gospel writers and affirmed in the letters of Paul.
Reference: Everything You Always Wanted to Know About God (but were afraid to ask): The Jesus Edition by Eric Metaxas, pp 13-23