Yeah, man. You might want to go ahead and assume that I know most of the fancy words.
Cool.
'Within period'?? Did you mistype? What does 'within period' mean?
You know all the fancy words ... but you don't know this?
What the actual charlie-foxtrot?
"Within period" means "Within the time between the alleged events and Celsus' writings."
As I've quoted, the Second John letter makes the accusation. So the Bible itself contains evidence that the accusation was made.
The 2 John statement doesn't mean what you seem to think it means. 2 John is arguing against a "spiritualist only" interpretation of the Resurrection, or of the Incarnation as a whole. The author of this epistle is not reacting to an accusation that Jesus never existed: rather, he is arguing against the doctrine that Jesus was entirely spiritual, either during his life or after his supposed resurrection.
2 John is anti-Gnostic, not anti-mythicist.
Are you aware that the (perhaps fictional) Celsus lived at least a hundred years after Jesus is claimed to have lived?
Can you refute the existence of any man who was claimed to have lived in 1914?
For you to make the claim that Celsus did not exist, you have to support your claim. WHether or not I can refute your claim is irrelevant until it is supported.