Why does the old Adam have to die for us to be right with God?

Les explains that when Adam sinned, the old sin nature became the only nature, and it is the nature every person is born with. To come back into a right relationship with God, that old Adam must die. It must be put to death by crucifixion, which is accomplished in the realm of the Spirit by God when we believe the Gospel. God then immediately places opposite the old Adamic nature a new nature, a new divine nature, which cannot sin because it is divine. When believers sin, Les says, it is because the old Adam has taken control for a moment, and it is through the old nature that they continue to sin. In God's eyes, old Adam is dead; that is why He can declare us justified, as if we had never sinned, because old Adam is dead and gone so far as God is concerned. Experientially, however, in everyday life, old Adam still affects the believer.