People have free will, thus, are capable of good or evil "on their own." No argument there. . .
People such as Hitler, Stalin, bin Laden, etc., are capable of GREAT evil and harm to others. Much of this can be explained by the predeliction of man for power, etc. BUT they are greatly tempted to great evil, and it does not seem necessary to disregard that they could be tempted in their human foibles by an evil ONE. . .
A temptation they could, nonetheless, choose to reject . . .
The implication being explored is also whether or not demonic power could have helped Hitler to achieve his great evil . . . speaking from a statistical standpoint, were the odds of his coming to power and staying alive greater than those of chance and human action alone? We will never know with scientific certainty. But that does not mean that those who leave open that possibility are unenlightened, benighted, etc. . . . We are not, after all, ignoring the laws of physical nature and human reason and will in the process of evaluating the events . . .As good observers using the scientific method, what is wrong with acknowledging other variables as yet unexplained? I don't think psychology, psychiatry, sociology, etc. claim to adequately explain the behavior of a Hitler with a scientific model . . .So Occam's Razor does not apply. There is no simple adequate scientific explanation available . . .
The same goes for doing good: we model the behavior we admire, and von Staufenberg, for example, modeled the Christian and noblise oblige worldview. He had the soul of a philosopher, the courage of a military hero. He could have chosen not to risk his life in an attempt to save Germany and save others. The psychologists, etc., can't scientifically model him, either. He sought counsel from a confessor the night before the attempt. (Going from memory here.) One could argue: He was trained for this type of response -- yet so many others raised in similar backgrounds did NOT do what he did. (Although there were more of them than most of us are aware of.) His religious and philosophic heritage certainly motivated him (and his brother and uncle) to take action and helped him to have the courage to go through with it.
Beamer prayed before he said "Let's Roll" -- how can you say that he would have had the courage and RESOLVE to do what he did without prayer? It is possible, I'd warrant, and some have done so. However, I would also posit that it is easier to do with prayer and supernatural grace. Thus, more good is done in a world open to prayer and grace than by human powers alone. Bush himself no doubt obtains his RESOLVE to fight this EVIL of terrorism from his faith, aided by the strength obtained by prayer. OK, don't believe it if you don't want to. I admire people who try to do the good and moral and right thing, without help from God. That's trying to do it the hard way!
You would probably enjoy Thomas Mann's Dr. Faustus. You can read the analogies either way: as a literary device (echoing the well-known tradition of Goethe's Faust, the epic poem about selling one's soul to the devil for temporal power). Or, you might possibly "hear" in the roar of the flames of Berlin in those final hours, the laughter of demons celebrating their masterful achievement . . . death, fire, destruction. Oh, they had no love for Hitler, either. His death, in time, was all to their liking, too. But look how much evil was accomplished by his uncanny ability to stay alive for so long . . .
Aquinasfan, bump me if you start a good vs. evil/power of the demonic thread with the implications raised by Goethe and Mann! Much food for thought . . . The literary aspects alone are phenomenal, even for those who do not believe in the literal power of the demonic . . .