Without proof?!
The fact that anyone believes is a miracle. I don't need to perform miracles to be a Christian. That word was first coined by the apostle Paul in Koine Greek.
Which was Χριστιανός - meaning - a follower of Christ
I looked up the definition of the suffix 'ian' and got:
(as a noun) native of, relating to.
Noun: related to, one that is
One doesn't have to perform physical miracles to be labeled as a Christian.
https://www.msu.edu/~defores1/gre/roots/gre_rts_afx3.htm?pagewanted=all
TOEFL Vocabulary Workshop