Daniel Kahneman and Amos Tversky legitimized behavioral economics—the study of how people really behave around money, as opposed to how economists say a rational person ought to behave.

Then Richard Thaler and Cass Sunstein applied the lessons of behavioral economics to everyday life with their book Nudge. The duo nudged so successfully that in recent years, their prescriptions have been put to work in corporate retirement plans—and even public policy—on a global scale.

When I spoke to Thaler to discuss his newest book, Misbehaving, a series of stories documenting the rise of behavioral economics, he told me that he has a message for those who seek to employ his methods:

“Nudge, for good.”

And why does he say that?