The case of Paul is interesting to consider in that it presents a real problem for non-Christians.
When you read his words, you feel them. They are beautiful, the works of a deep mind. He is perhaps the greatest writer of all time, and his writings laid the foundation of Western literature for the next 2,000 years.
In these writings he references many miracles that he either performed himself or witnessed others performing. Including a vision of Jesus Christ and accounts of hundreds of others also seeing Jesus Christ.
Paul worked so hard to keep his writings truthful. This is evidenced by the many places, people, politicians, and even local businesses that he mentions, which have all been subsequently verified by outside sources.
Non believers who attempt to dismiss Paul’s preachings must either call him a madman, or a liar.
His writings make either line of attack virtually impossible to land. He is clearly not a madman. His writing is clear, humble, beautiful, and inspiring. As to being a liar, he made numerous claims that in 2,000 subsequent years have all been shown to be accurate. Likewise, there is no record of anyone in his own time refuting any of his claims.
Paul thus represents a real problem for non believers, in that he can’t be both the greatest writer of all time, filled with wisdom and insight, while also being crazy. Likewise, he can’t be the epitome of truth, while at the same time being a liar.
Then add to all of this, the fact that he can’t even be accused of doing it for fame or fortune. In his own time, he was a Roman citizen. The height of prestige. He gave up the comforts this offered him in order to preach the gospel. He didn’t take wages from his followers, but instead made his living and funded his missionary work by making tents.
Ultimately facing death by beheading at the orders of Nero.
Simply put, A man like Paul cannot exist, unless he is standing on a foundation of truth. The works of Paul therefor seem to be self-evidence of the things they proclaim.
Thus providing an almost impossible problem for those who do not believe In Jesus Christ to deal with, short of just choosing to ignore the testimony of Paul, and persisting in non-belief despite it.