How do we know man is totally depraved?

The doctrine of total depravity teaches that man, because of the fall, is entirely incapable of saving himself. Romans 5:12 informs us that sin entered the world through one man, Adam, and death through sin, leading to the condemnation of all humanity. Genesis 6:5 further illustrates this by describing the thoughts of man's heart as 'only evil continually.' This underscores that without divine intervention, humanity remains in a state of spiritual blindness and death, completely helpless to rescue themselves from sin.