 Hypoxia: Aisha is out flying her small, unpressurized airplane, wondering whether she has enough fuel to make it to Hawaii. She looks at the gauges, dials, and maps, and obtains some evidence, E, which she knows strongly supports (say to degree .99) either the proposition that she has enough gas (G) or that she does not (~G). Thinking it over and performing the necessary calculations, Aisha concludes G; in fact, this is what E supports. But then she checks her altitude and notices that she’s at great risk for hypoxia, a condition which impairs one’s reasoning while leaving the reasoner feeling perfectly cogent and clear-headed. Aisha knows that at this altitude, pilots performing the kinds of calculations she just did only reach the correct conclusion 50% of the time.