Our doctrine becomes uncertain, darkness obscured as it is by the darkness surrounding the Devil. But our curiosity, excited by the certainly of his multiple existence, has a right to raise two questions. But this diagnosis is too extensive and difficult for Us to attempt to probe and authenticate it now. The problem of evil remains one of the greatest and most lasting problems for the human mind, even after the victorious response given to it by Jesus Christ. Grace is the decisive defense.
Innocence takes on the aspect of strength.
May Our apostolic blessing also be a help toward achieving this. See St. Augustine, Soliloquies. See the Gloria of the Mass. See Rom 7. Romans 5, 12.