Scientific communities have frequently denied claims that later prove justified: such episodes are used in debates about the conventions that govern decisions about matters of fact. Instructive cases of such decisions and reversals occurred during a serious crisis of facts that erupted in Enlightenment Europe from the 1780s. Establishment of scientific facts relied on appropriate groups to produce and judge them, but during such periods of radical social instability, these systems were in trouble. Notions of popular superstition and of over-sophisticated imagination were then used to manage fact claims. Plebeians were reckoned superstitious and incapable of imagination; genteel elites could seem too prone to imaginative fancy, too skeptical of received doctrine. Examples of the late Enlightenment fact crises especially evident during controversies around animal magnetism, which seemed to dramatize refined vulnerability to imagination, and around aeroliths, the widespread and allegedly vulgar superstition that stones could fall to Earth, illuminate issues of authority and evidence that continue decisively to affect public sciences, traditional customs, and their claims to produce effective factual knowledge.