When the Doctor asks if he is a good man perhaps what he really wants to know is whether he is abusing his power. The thrill of and even addiction to power is a recurring theme in series eight. Weve seen Clara struggle with her need to control as her attention seeking behavior at times overrides her empathy. The Master and the Doctor are mirrors of each other. The Master has completely lost sight of the beauty of the universe. She represents the voice of the jaded and cynical the people who refuse to see beyond their own selfishness and greed. To them power is a means to an end. To the Doctor power is a tool and one he uses warily. He loves the thrill of adventure but he is aware what may happen if he allows himself to believe his own hype.