"Let no man deceive himself. If any man among you thinks that he is wise in this age, he must become foolish, so that he may become wise. For the wisdom of this world is foolishness before God. For it is written, 'He is THE ONE WHO CATCHES THE WISE IN THEIR CRAFTINESS'; and again, 'THE LORD KNOWS THE REASONINGS of the wise, THAT THEY ARE USELESS.' "
Men deceive themselves when they equate knowledge with wisdom. Wisdom is seeing life from God's perspective, and apart from a changed life through the salvation that is found only in the Lord Jesus Christ, man will not naturally have God's perspective. Until, or unless one is given the fear of the Lord (which is the beginning of wisdom, Prov. 1:7), he will live life foolishly, with no spiritual reward. Indeed, all his "good" deeds will only serve to heighten the justified condemnation received at the Great White Throne judgment.
Meanwhile, why are the reasonings of the "wise" man (in the world's opinion) useless from the Creator's perspective? It is because the spiritual dimension is inoperable. The unchanged individual is spiritually separated from God (Ephesians 2:1), unable to understand the things of the Spirit (I Corinthians 2:14), because such require spiritual discernment. Consequently, without spiritual revelation upon which to act, the unbeliever has only speculation to work with in the realm of spiritual truths. Refusing to accept what God has revealed, he is left with guessing, surmising, and "common sense" assumptions for guidance. Such reasonings from a deceived and deceitful heart (Jeremiah 17:9), based on self-effort rather than faith (Hebrews 11:6) are unacceptable to the living God. What, then, is acceptable?
"...he must become foolish..." What the world calls foolish is to submit one's life to an unseen Being, who may or may not be trustworthy. To live a life ordered by such trust is viewed by the unbeliever as the height of foolishness. Why? The entire world system operates on Satan's pernicious and pervasive lie: "This (what you understand with your senses) is all there is." To "become foolish" (from the Creator's vantage point) is to abandon the works-approach to God, and come to Him as He requires: through trusting the Lord Jesus Christ alone for acceptance. Only He can change from the inside, out. He alone transforms spirit, soul, mind, and body.
Each and every one of us is a fool for someone. The one who says in his heart "there is no God" is a fool for Satan and his agenda. The one who has been changed by the Lord Jesus is to be a "fool" for Him, becoming all things to all men that more may be saved (I Corinthians 9:19).