For the message of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God. 1 Corinthians 1:18
Christianity has never been without its skeptics. For those who believe wisdom is acquired only through science and reason, Christianity is foolish.

Paul in Athens, Raphael
In Paul’s letter to the Corinthian church (1:18-25) he sees 2 groups that are skeptical of the Gospel: cultured Greeks and devout Jews.
The Jewish leaders demanded a sign (1:22; John 6:30). They expected God to meet their criteria for wisdom by providing irrefutable and tangible proof. They envisioned the Messiah as one who would demonstrate power and majesty, so a crucified Messiah was a contradiction in terms.
They pointed to their own law which said, “anyone hung on a pole is under God’s curse” (Deuteronomy 21:23).
Cultured Greeks sought wisdom through reasoning and argument. They were enthralled with sophisticated words. In an unsuccessful mission trip to Athens, the author of Acts observed that those “who lived there spent their time doing nothing but talking about and listening to the latest ideas” (Acts 17:21). To them a Christian preacher with a blunt message was a crude and uncultured person. He was to be ridiculed, rather than to be listened to and respected (Acts 17:32).
The Christian message has always disappointed those requiring tangible evidence or airtight logic. To them, Christianity is foolish. However rational and meaningful the message of the cross is to us, we cannot respond to the arguments of worldly wisdom only with words.
God has made himself unknowable by human wisdom. He has made himself known in a crucified Messiah, which is offensive to some and irrational to others. God’s answer to the wisdom of the world is to act in power: His power to save and to change men and women is the most persuasive response to skeptics (1 Corinthians 1:18).
This wisdom may seem both foolish and weak, but it is far wiser and stronger than anything worldly wisdom can offer (1 Corinthians 1:25).