What does Proverbs 12:15 mean?

One of the primary hallmarks of a "fool," in Scripture, is summarized here. The root word 'eviyl, in Hebrew, means a hardened, thickheaded person who will not listen to reason. This is not a person lacking intelligence, but someone who refuses to let sound advice penetrate his head. The same concept is applied in Proverbs 1:7 as a fundamental reason why people don't respond to godly truth. Proverbs chapter 10 reflects this kind of "foolishness" multiple times.

A fool rejects the counsel nature provides that God exists (Romans 1:19–20). He convinces himself that there is no God. Psalm 14:1 declares, "The fool says in his heart, 'There is no God.'" A person may have a PhD, but he is a fool if he denies the existence of God.

Furthermore, a person who trusts in riches instead of in God is a fool. In a parable, God called a certain rich farmer a fool because he trusted in a bountiful harvest instead of in God. God said to him, "Fool! This night your soul is required of you, and the things you have prepared, whose will they be?" (Luke 12:20). Proverbs 14:12 assures us "there is a way that seems right to a man, but its end is the way to death." By contrast, a wise man heeds advice. He accepts nature's testimony that God exists. He takes to heart the instruction Scripture gives him. He follows God's will and not his own.