Sometimes lying is simply kinder. Your friend asks, "Does this outfit make me look fat?" as she runs out the door for a date. The right answer is no, says Randy Cohen, who writes The Ethicist column for The New York Times Magazine. Had she asked earlier, you could have told her the black dress looked better. Softening the truth of a harsh world for children is also OK, says Geri Kerr, a marriage and family therapist in Hackettstown, New Jersey. Other times a lie is not just permissible, but obligatory. A classic example: It's the 1850s, and you have a houseful of slaves on the Underground Railroad. "If telling the truth will cause harm and your action is altruistic, you must lie," says Cohen. The bad news: lying to your boss about being sick? No-go, says Cohen. "You can't lie just because it's convenient." Oh well.