Willpower: Rediscovering the Greatest Human Strength

by Roy F. Baumeister

He needs the help of “bright lines,” a term that Ainslie borrows from lawyers. These are clear, simple, unambiguous rules. You can’t help but notice when you cross a bright line. If you promise yourself to drink or smoke “moderately,” that’s not a bright line. It’s a fuzzy boundary with no obvious point at which you go from moderation to excess. Because the transition is so gradual and your mind is so adept at overlooking your own peccadilloes, you may fail to notice when you’ve gone too far. So you can’t be sure you’re always going to follow the rule to drink moderately. In contrast, zero tolerance is a bright line: total abstinence with no exceptions anytime. It’s not practical for all self-control problems—a dieter cannot stop eating all food—but it works well in many situations. Once you’re committed to following a bright-line rule, your present self can feel confident that your future self will observe it, too. And if you believe that the rule is sacred—a commandment from God, the unquestionable law of a higher power—then it becomes an especially bright line. You have more reason to expect your future self to respect it, and therefore your belief becomes a form of self-control: a self-fulfilling mandate. I think I won’t, therefore I don’t.