The Romans were simultaneously the most practically minded people in the ancient world and among the most superstitious. This is not a contradiction. Superstition — the belief that specific acts, objects, words, and encounters have causal effects on outcomes beyond what rational analysis can explain — tends to flourish precisely among people who need reliable outcomes and who have incomplete knowledge of the mechanisms that produce them. The Romans needed reliable harvests, reliable military victories, reliable births, and reliable business outcomes. Their practical knowledge of how to achieve these things was considerable but not complete. The gap between what they knew and what they needed to know was filled by omens, amulets, spells, and the accumulated lore of good luck and bad luck that constituted Roman superstition.