I offered to do a favor for a friend yes­ter­day and got the usual response: “I’ll owe you one.” This trans­ac­tion always makes me uneasy, and I am usu­ally quick to protest that no, noth­ing is owed. I don’t say that because it’s polite, and I don’t think peo­ple lack com­pelling things to offer in return. I say it because I already feel indebted, and any kind­ness I show is an effort to cor­rect at least a lit­tle of an insur­mount­able imbalance. […]