The evidence of St. Paul is merely hearsay.

The Catholic Answers

Even had not St. Paul seen the risen Christ personally, his evidence would not be unreliable. If we demanded that no historian should set down anything except that which he had actually witnessed for himself very little history would be written. So long as the historian knows that the source of his information is reliable he is free to record his information. St. Paul did have the testimony of many and independent eye-witnesses, and would quickly have detected conflict in their accounts. But in addition to the evidence of other eye-witnesses, St. Paul personally saw the risen Christ. In Acts IX., he is converted by Christ in person. In I. Cor. XV., 8, he writes, “And last of all He was seen also by me.” In I. Cor. IX., 1, “Have not I seen Christ Jesus Our Lord?” Again in I. Cor. XL, 23, “For I have received of the Lord that which also I delivered unto you.” St. Paul could hope to gain nothing in this world or the next by lying. His doctrine led to his martyrdom in this life, and as for the next, he himself taught that God hates liars.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty