The Gospels are eye-witness testimony by the named authors, and that's why we can cite them as evidence. If the Gospels were written by anonymous authors writing down what they heard somebody say they heard from someone else, then they'd just be hearsay and wouldn't count as evidence.
These eyewitness accounts are extraordinary. Take the Gospel of Luke, for example. For this to be an eyewitness account, then Luke would have had to
- witness the conversation between Mary and the angel telling her that she's going to become pregnant
- follow Mary and Joseph around Bethlehem watching them go from inn to inn looking for a room
- witness Mary giving birth to Jesus
- sprint out to the pastures so he could witness the angels announcing the birth of Christ to the shepherds
- sneak into Herod's palace on multiple occasions to witness private conversations between Herod and his advisers
- follow the three eastern kings around and witness the conversation between them and the angel
- follow Jesus and the disciples around so he could record everything they did
- and beat everyone else to the tomb Sunday morning so he could record what happened there.
Furthermore, he would have had to do all of this without being noticed by anyone, so that when the apostles met Luke the Physician for the first time in Acts, he could play dumb and pretend that he didn't know about any of this. Why did he do that? I guess he just didn't want them to think he was a weirdo. "Um, yeah, I already know all about it. I've been sneaking around following all of you and writing down everything you did for the last 40 years."
Now, you may be asking, how could one man have been in all of those places at those times? The answer is obvious. God must have been telling him where he needed to be and to write down what he saw. Therefore, the unlikeliness of these eyewitness accounts is proof that the Bible is inspired by God.
Pastor Billy-Reuben