To sell well is to convince someone else to part with resources—not to deprive that person, but to leave him better off in the end. That is also what, say, a good algebra teacher does. At the beginning of a term, students don’t know much about the subject. But the teacher works to convince his class to part with resources—time, attention, effort—and if they do, they will be better off when the term ends than they were when it began.
