How do we know that mankind is totally depraved?

The doctrine of total depravity is grounded in Genesis 3, where the disobedience of Adam leads to sin entering the world, bringing death to all. Romans 5:12 states, 'Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned.' This illustrates that through Adam's transgression, every person is born into a corrupted state, unable to achieve salvation on their own merit. Therefore, total depravity encompasses not just an absence of goodness, but a nature inclined towards sin, necessitating divine intervention for redemption.