Numerous classical authors report that natural phenomena played an essential part in one of their most sacred religious rituals: the oracle at Delphi. According to the geographer Strabo (c. 64 B.C.–25 A.D.), for example, "the seat of the oracle is a cavern hollowed down in the depths … from which arises pneuma [breath, vapor, gas] that inspires a divine state of possession" (Geography 9.3.5). Over the past five years, a team of researchers -- a geologist, an archaeologist, a chemist and a toxicologist -- has put that claim to the test, making it much more likely that we will actually...