Jesus said there is only one unforgivable sin, and that is blasphemy of the holy ghost. Now here is the question, what exactly is the blasphemy of the holy ghost. Jesus rebuked the pharisees for calling him a false prophet or something like that, and Jesus considered that to be blasphemous.
I'll tell you what I think. I think it is almost downright impossible to blasphemy against the holy ghost. I think that it requires someone seeing God performing a miracle right in front of their eyes, and them denying that it happened or attributing it to satanic forces.
Tell me what you guys think.