Argument from scriptural 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 physical 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 of these events.
Imagine taking a number of tribesmen from New Guinea and subjecting them to a magic show. Afterward it would be possible to collect as many testimonies as desired to the "fact" that, for example, the magician was beheaded by a guillotine, but was re-integrated and completely unharmed several minutes later. These testimonies are contemporary (indeed, as contemporary as is possible) and mutually corroborative, Moreover, these witnesses could be question to any degree. What would be our reaction? Would we take these testimonies as evidence and conclude, based only on them, that the magician really did have his head cut off and survive? 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?