How do we know man is spiritually dead by nature?

In Genesis 2:17, God warned Adam that eating from the tree would result in death. While Adam lived physically for many years, he and humanity died spiritually the moment they sinned, losing the life of God, which is inherent holiness, truth, and righteousness. This spiritual death is underscored in Romans 5:12, which states that sin entered through one man, causing death to spread to all men. Consequently, since man is dead in trespasses and sins (Ephesians 2:1), only God can impart new life, demonstrating the urgency of divine intervention for salvation.