The Bible.
"The Bible doesn't count."
The Church has an extensively documented history of miracles over the past two thousand years.
"You can't use anything from the Church."
Two billion one hundred eighty million people believe today (when have that many people ever believed in a single idea?).
"They are all deluded by the Church."
No archeological or historical record has contradicted any historical record from the Bible, while numerous archeological and historical records have corroborated events in the Bible.
"Just because something hasn't been disproven, that doesn't mean that it is proven, and I already told you that you can't use the Bible."
People I know, including my previous pastor, witnessed a miraculous appearance of Christ's image during a Eucharistic adoration.
"Did you see it?"
No.
"Hearsay."
My mother had a miraculous transformation of both her sight and, more recently, a rosary.
"There's no proof that God did that."
... I haven't strangled you yet.
"Now ... that might just be a miracle ..."