Externality and taboo: Resolving the Judaic pig puzzle

Originally published in Rationality and Society

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Judaic law famously bans pigs. For millennia, scholars have wondered why. This paper uses the economics of property rights to resolve the puzzle. We argue that the Judaic pig ban was an instrument for internalizing swine externalities. Free ranging pigs in search of sustenance trespass on agricultural landowners’ property, wreaking destruction. Activities that foster such pigs thus create negative externalities that can cripple agricultural economies. When the expected cost of swine externalities becomes large, internalization becomes worthwhile: lawmakers with a vested interest in the agricultural economy ban activities that foster free ranging pigs. That is what transpired in ancient Judah, where lawmakers were priests whose livelihoods depended on agriculture, where all swine ranged freely, and where the expected cost of swine externalities surged during the late Iron Age. Lawmakers invoked God to enjoin involvement with pigs because a supernatural injunction was cheaper to enforce than a natural one: in a land of faithful Hebrews, Yahweh’s swine prohibition enforced itself. The Judaic pig ban’s features are consistent with pig bans recently adopted by US states such as Montana, which everyone agrees are instruments for internalizing swine externalities.