“But the natural man does not receive the things of the
Spirit of God, for they are foolishness to him; nor can he know
them, because they are spiritually discerned.”
1 Corinthians 2:14 

The natural man is not complete. He is a person that is interested in the physical world only, the “here and now” rather than the future. He lives without spiritual aspect of his nature. There is a void within him. He has no desire to know God or His Word. The natural man is far from God, guilty before God, and condemned by God.

Billy Graham says, “The heart of man is filthy and needs the cleansing that only Jesus Christ can give. The heart of man is guilty and needs the forgiveness that only Jesus Christ can give. Without God, the best man in the world is capable of the most terrifying crimes in this life.”