This essay argues that the motifs of divine vengeance present in the Histories represent a conscious, considered theory of divine action in the world. This theory is the result of Herodotus’ empirical methodology, and is defined by an admitted lack of access to poetic revelation or other actual insight into the motivation and nature of divinity. Instead, Herodotus’ theory is based on his own analysis of historical events on a large scale. Divinity possesses a basically regulatory role in the cosmos, ensuring that history follows certain consistent patterns. One such pattern is vengeance, by which a large-scale balance of reciprocity is maintained in human events through acts of repayment carried out with the support of divinity. This theory underlies Herodotus’ historical project, reinforcing his general skepticism about human knowledge and power and making possible his universalizing approach to historical narrative.