In his account of the Persian wars, Herodotus tells how the Lydian king Croesus consulted the Delphic oracle, asking whether he should go to war with Persia. If Croesus attacks the Persians, said the oracle, he will destroy a mighty empire. Croesus confidently marched on Cappadocia, but it was his own mighty empire that he destroyed by doing so, not that of the enemy king, Cyrus. Other oracular pronouncements were equally ambiguous. According to Ennius, “Aio te Romanos vincere posse” (quoted by Shakespeare in Henry VI, Part 2) was the answer that Pyrrhus, king of Epirus, received when he asked about making war with Rome: “I assert that you can conquer the Romans/the Romans can conquer you.” The lesson is clear: listen carefully to those whom you consult—they may not be saying what …