Why is the old Adamic nature prone to rebelling against God?

Les explains that Paul had been constantly hammering home our need to deal with old Adam, the sin nature with which we are born. The multitudes of the human race are existing under the control of that old Adamic nature, which is prone to rebellion and to doing that which is contrary to the will of God. The reason for this inclination is that the old nature is under the control of God's greatest adversary, Satan. Les also notes that he had mentioned a verse in a past program, forgotten what it was at the time, and now plans to use it.