What does the Bible say about the natural man's ability to understand God's word?

According to 1 Corinthians 2:14, the natural man does not accept the things that come from the Spirit of God because they are foolishness to him, and he cannot understand them since they are spiritually discerned. This highlights a fundamental truth in Reformed theology: human beings are spiritually dead in their sins and cannot comprehend the gospel or the truths of Scripture apart from divine revelation. It requires a transformation through the Holy Spirit for one to have spiritual discernment and believe in Christ. This lack of ability underscores God's grace—the necessity for the Holy Spirit to regenerate the heart, enabling true understanding and faith.