Why do we call people without Christ “lost?” Dr. John MacArthur teaches us why the cross is foolishness to the unbeliever:
“Unregenerate sinners are completely lost.
Unaided and unilluminated, in his natural condition and without the gospel, the sinner will never find a way to God. In fact, he won’t be looking for it to begin with. “A natural man does not accept the things of the Spirit of God, for they are foolishness to him; and he cannot understand them, because they are spiritually appraised” (1 Corinthians 2:14). He’s spiritually dead and blind, with no hope of finding God on his own.
But even when sinners are presented with the gospel of the cross, they reject it. First Corinthians 1:18 says, “For the word of the cross is foolishness to those who are perishing.” Even when a sinner has been shown the only way of salvation, he will ignore and dismiss it. On the other hand, 1 Corinthians 1:18 goes on to say, “But to us who are being saved it is the power of God.” Man’s supposed wisdom—the very thing that natural theology tells us will lead him to God—forces him to reject the message of the cross and the only power there is that can save him.
What does God think of man’s wisdom? Paul continues in 1 Corinthians 1:19–20: “For it is written, ‘I will destroy the wisdom of the wise, and the cleverness of the clever I will set aside.’ Where is the wise man? Where is the scribe? Where is the debater of this age?” In other words, bring on the finest minds, the most articulate communicators, the best debaters—give me the elite, and I will show you a group of fools. In Acts 17, Paul is in Athens, and Scripture says, “His spirit was being provoked within him as he was observing the city full of idols” (Acts 17:16). In the Areopagus—the gathering place for all the philosophers and intellectuals of the day—he boldly confronted their laughable ignorance and proclaimed the only message by which they could be saved.
Men of Athens, I observe that you are very religious in all respects. For while I was passing through and examining the objects of your worship, I also found an altar with this inscription, “To an Unknown God.” Therefore what you worship in ignorance, this I proclaim to you. The God who made the world and all things in it, since He is Lord of heaven and earth, does not dwell in temples made with hands; nor is He served by human hands, as though He needed anything, since He Himself gives to all people life and breath and all things; . . . for in Him we live and move and exist, as even some of your own poets have said. . . . Therefore having overlooked the times of ignorance, God is now declaring to men that all people everywhere should repent, because He has fixed a day in which He will judge the world in righteousness through a Man whom He has appointed, having furnished proof to all men by raising Him from the dead. (Acts 17:22-31)
These were perhaps the finest minds in the world at the time, and the best they could do was put up a placard to serve as a safety net for any deities they had overlooked. That’s maybe the best you can hope for from natural theology—the guilty sensation that you might have overlooked the true God of the universe.
Back to 1 Corinthians 1, and the pinnacle of the passage in verse 21: “For since in the wisdom of God the world through its wisdom did not come to know God, God was well-pleased through the foolishness of the message preached to save those who believe.” That’s effectively the Great Commission in different words. The only hope of salvation is through the preaching of the cross. Paul acknowledges that such a message is a stumbling block to Jews, and pure stupidity to Gentiles (1 Corinthians 1:23), and he’s right. From a human perspective, believing that the horrific, humiliating death of a Jewish carpenter more than two thousand years ago has any impact on modern life—let alone offers any sort of substitutionary atonement for our sins—sounds like madness. But as Peter boldly exclaimed to the priests and leaders of Israel, “There is salvation in no one else; for there is no other name under heaven that has been given among men by which we must be saved” (Acts 4:12).
Why is that salvation found in Christ alone? Paul gives us the answer in 1 Corinthians 1:29-31,
So that no man may boast before God. But by His doing you are in Christ Jesus, who became to us wisdom from God, and righteousness and sanctification, and redemption, so that, just as it is written, “Let him who boasts, boast in the Lord.”
Ultimately the gospel is not for the proud, the arrogant, or those who believe they can get to God by themselves. God intentionally chose a foolish message to humble us and to guarantee that no one would boast in his or her own intelligence. He chose the cross to stifle any inclination in us to think we got to Him on our own. All the glory goes to God.”
https://www.gty.org/library/blog/B180919
