Via Andrew Sullivan:
"Tyranny starts as a habit; it has the tendency to, and generally finally does develop into a disease. I believe that habit may coarsen and stultify the very best of men, reducing them to the level of brutes. Blood and power make a man drunk: callous coarseness and depravity develop in him; the most abnormal phenomena become accessible, and in the end pleasurable to the mind and the senses. The human being and the citizen perish forever in the tyrant, and a return to human dignity, to repentance, to regeneration becomes practically impossible for him," - Fëdor Mikhailovich Dostoevsky, "Memoirs from the House of the Dead."