How did Edward Westermarck study differences among moral systems?

Edward Westermarck studied differences among moral systems by employing a comparative sociological and anthropological approach, which he detailed in his influential work, The Origin and Development of the Moral Ideas (1906–08).12

Rather than establishing rules for conduct, Westermarck sought to describe and analyze the vast diversity of moral attitudes across different cultures. He systematically compared how various societies approached a wide range of issues, including:12

• Life and Death: The wrongness of killing, encompassing warfare, euthanasia, suicide, infanticide, abortion, human sacrifice, and dueling.2
• Social Duties: Obligations to support children, the aged, or the poor, as well as the status of women and the holding of slaves.2
• Conduct and Belief: The duty to tell the truth, dietary restrictions, property rights, theft, concern for nonhuman animals, and duties to the dead and the gods.2

By demonstrating this tremendous diversity, Westermarck argued that moral judgments are based on emotions of approval and disapproval rather than objective truths.12