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.
1 Corinthians 2:14
14 But the natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned.
Because they did not receive the love of the truth. 2 Thess. 2:10