We imagine science as an open-ended pursuit in which doubt is encouraged, new evidence is welcomed, and theories are revisable. The basic sciences operate roughly like that. But “regulatory science,” in which conclusions are required on a deadline, works differently. A drug must be approved or not, a level of pollution pronounced safe or not. In these circumstances, Eyal explains, the authorities must at some point close the case, push errant facts aside, and draw a line. Such moments generate “inevitable friction.”