Not saved by works lest we boast, Eph. No flesh can be saved by works. The only saving work is faith, Jn. Our goodness is dirty rags to God. Saved by grace or not at all.
Experience is the best test of the truth.
Natural mind can't understand the Bible. God's secrets are only for those who trust Him. Mind is blinded by Satan. Some people don't want to believe. If Gospel is foolish, it is a sign you perish.