Argument from biblical miracles
The argument from biblical miracles states (more or less) that because the Bible claims that people witnessed miracles performed right in front of them by Jesus, we can therefore believe that they happened—which confirms Jesus's claims to be God.
(Double) Standard of Evidence
Since there can be no archaeological evidence of a man walking on water, or feeding 5000 with five loaves and two fishes, or turning water into wine, we are left solely with testimonial attestation.
Imagine taking a number of tribesmen from New Guinea and subjecting them to a magic show. At the end, it would be possible to collect as many testimonies as desired to the "fact" that, for example, David Copperfield was sliced in half by a giagantic circular saw, and was re-integrated and completely unharmed minutes after that. These testimonies are contemporary (indeed, as contemporary as is possible) and mutually corroborative - what would be our reaction? Would we take these testimonies as evidence and conclude, based only on them, that Copperfield really did saw himself in half? Or would our incredulity at the likelihood of the event override the testimonies and lead us consider other alternatives (the tribesmen were fooled/they aren't remembering correctly/they're lying).
Would adding two thousand years of possible embelishment and distortion make the testimonies more, or less, credible?