My point is, whether or not you really did exist, and they can't know for sure, you are more likely to exist, with them having found a record of 'misterwhite' than if at that instant someone made up the name 'kljljlkjlj' and wondered if 'kljljlkjlj' actually existed.
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This may be true for ordinary claims such as "a person named Jesus lived", but much less so for extraordinary claims such as "a person named Jesus rose from the dead." We know that people can live and if a contemporary left some record of a person living, then that is credible evidence for the claim that a person lived at the time the contemporary lived. We have no evidence of anyone rising from the dead so a claim made 2000 years ago by someone who was a contemporary of a person they claim rose from the dead is hardly credible evidence. (Not to mention that there isn't a contemporary record of Jesus rising from the dead.)