That Amazon search confirmed my suspicion: Gratitude is a common topic of inspirational literature. You can get gratitude journals, gratitude calendars, gratitude guides, gratitude cards, gratitude with attitude books, probably gratitude mugs and teacups and bumperstickers and bracelets and decals and tattoos. What is almost completely absent is any serious examination of the theology, philosophy, ethics, or politics of gratitude.

To give the experiment a control group, do that same Amazon search on “justice” or “love” or any of a dozen other emotions and/or virtues.