The concept of willpower is frequently sourced to Rene Descartes, the 17th-century philosopher who championed the idea of free will as “the ability to do or not do something.” Later, psychologists explored the mental processes—impulses, desires, ambitions—that lead us to act, or not act, when an urge strikes us. But for something that looms so large in the minds of the public—and would make for one hell of a pharmaceutical windfall if you could put it in a pill—the way that willpower actually works remains strangely mysterious. Could it be because there’s no such thing?