We live in an unfair universe. Like all primates, humans have strong negative reactions to perceived unfairness; thus we find this fact stressful. There are two popular methods of dealing with the resulting cognitive dissonance. First, one may change one's view of the facts - deny that the unfair events took place, or edit the history to make it appear fair. Second, one may change one's morality - deny that the events are unfair.
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