“To do evil a human being must first of all believe that what he's doing is good.”

The concept is sufficiently correct to get 5 stars from my perspective BUT (and that is a big but), much evil is simply done for the pleasure of it (a sick enjoyment of inflicting pain for example) and a multitude of reasons other than the pursuit of good. To support the quote for example, such things as are reported concerning the chief executive are;
http://www.eutimes.net/2013/01/obama-death-squads-kill-top-gun-activists-as-new-massacre-fears-rise/

That's why the "true believers" are the most dangereous.

Fanatics of all stripes have committed the worst atrocities with a clean conscience.

Amazing quote. I'll try to use it in my writings from now on. I'm really eager for reading Solzhenitsyn's work.