An extensive corpus of ancient Mesopotamian (ca 1800--100 BCE) scribal knowledge survives in the form of text series entitled šumma P “If P.” The “if P then Q” statements establish systematic correspondences between visible, imaginable or conceivable physical phenomena on one hand, and events in the human social world on the other. They represent the written repertoire of ominous signs, the focus of scholarly divination. This talk is concerned with the conditional formulation of omens and their particular style of reasoning.