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Unfortunately for ethical egoism, the claim that we will all be better off if every one of us does what is in his or her own interest is incorrect. This is shown by what are known as "prisoner's dilemma" situations, which are playing an increasingly important role in discussions of ethical theory... At least on the collective level, therefore, egoism is self-defeating - a conclusion well brought out by Parfit in his aforementioned Reasons and Persons.
