How did sin enter the world through Adam?
Through one man, Adam, sin entered the world when he fell in the Garden. His transgression brought death, and death passed upon all men because all sinned. The old Adamic nature entered, resulting in spiritual death for the human race, so every person is born dead.
Les teaches that justification by faith and faith alone is needed because of what happened in the Garden when Adam fell and death came with sin. Paul concludes in Romans 5:12 that by one man, Adam, sin—the old Adamic nature—entered into the world, and death came with sin, so death passed upon all men for all have sinned. The two become synonymous. Until the law, sin was in the world, but sin is not imputed when there is no law. Nevertheless, death reigned as a king from Adam to Moses, even over those who had not sinned after the similitude of Adam's transgression. The human race now faces the dilemma of being sinners and in a circumstance of death; spiritual death has already taken place, and we are born dead.
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: