This paper presents a game-theoretic rationale for the beneficial effect of a common enemy on cooperation. In a defence game against a common natural threat, the value of the public good of defence is equal to the sum of the players' defensive efforts. The game therefore takes the form of a...

This paper presents a game-theoretic rationale for the beneficial effect of a common enemy on cooperation. In a defence game against a common natural threat, the value of the public good of defence is equal to the sum of the players’ defensive efforts. The game therefore takes the form of...