Cognitive Dissonance

“Faced with the choice between changing one’s mind and proving that there is no need to do so, almost everyone gets busy on the proof.” 
John Kenneth Galbraith 

Cognitive dissonance is the mental discomfort (psychological stress) experienced by a person who simultaneously holds two or more contradictory beliefs, ideas, or values. The occurrence of cognitive dissonance is a consequence of a person performing an action that contradicts personal beliefs, ideals, and values; and also occurs when confronted with new information that contradicts said beliefs, ideals, and values.