In early times, Christians quite frequently used miracles to show that God exists and that Jesus was the Son of God. Not only do the gospels record many miracles performed by Jesus, Acts of the Apostles tells us that Peter was able to perform miracles that were even more astonishing than those performed by Jesus. Many brought the sick, just to let Peter's shadow pass over them and they would be cured.
In the days of lrenaeus, about the end of the second century, the resurrection of the dead was very far from being esteemed an uncommon event. The miracle was frequently performed on necessary occasions, by great fasting and the joint supplication of the church of the place, and the persons thus restored lived afterwards amongst them many years. In spite of the many victories over death, there remained those who were sceptical of the power of Christian miracles. A noble Grecian promised Theophilus, bishop of Antioch, that, if he could be gratified with the sight of a single person who had been actually raised from the dead, he would immediately embrace the Christian religion. For some reason, the prelate, however anxious for the conversion of his friend, thought proper to decline this fair and reasonable challenge.
Miracles remain a matter of faith to this day. Those who already believe God exists usually believe in miracles, at least in biblical times. Those who do not believe God exists do not believe that miracles happen. Of course, if a modern Christian could ever show unambiguous and incontrovertible evidence of even one miracle, then many would believe.