Evolutionary accounts of the origins of human morality may lead us to doubt the truth of our moral judgments. Sidgwick tried to vindicate ethics from this kind of external attack. However, he ended The Methods in despair over another problem - an apparent conflict between rational egoism and universal benevolence, which he called "the dualism of practical reason". Drawing on Sidgwick, we show that one way of defending objectivity in ethics against Sharon Street's recent evolutionary critique also puts us in a position to support a bold claim: the dualism of practical reason can be resolved in favor of impartiality.
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