Sorry, I stopped short of giving a complete answer before to this part. Had to run.
Corroboration is good of course. But what is missing in that, is hearing His voice. The Pharisees, for example, knew the scriptures quite well, but did not know Christ by His voice--mainly, because they expected something else, and were blinded by their own assumptions. Meanwhile, Israel was led by the spirit, as are we, and the exception that raises above the understanding of men, is what comes from God most commonly initially misunderstood.
Which creates the dilemma we are all faced with: Waiting to see if a claim comes to pass is all well and good after the fact, and if a claim aligns with scripture, that is also good. But that is not the pattern of the past--not completely. Therefore, Jesus said, "My sheep hear My voice"--because going forward--just as Peter came to know that Jesus was the Christ--not by study, not entirely by corroboration with scripture--was to be the way going forward. Which is not so different than what was before...it's just that we have also now heard it from Jesus that the only confirmation is spiritual, to which He specifies would come as if by His own voice. Which we know by what is written, came with rejection, with correction, with woe, and yet also good news with authority. But hearing does not easily come to those who are not silent and waiting with expectation.