The American business guru Clayton Christensen often tells a story from his days as a student at Oxford. He played basketball for the university team, and they made it to the national finals – whereupon it emerged the big game would be on a Sunday. Christensen is a devout Mormon, and playing on the Sabbath offended his principles. The team coach asked him to break his rule, just this once; Christensen prayed to God for guidance, and concluded that he couldn't play. So he didn't. That's the end of the story.
Unless you're deeply religious, you may find this anecdote doubly alienating: first because it smacks of halo-polishing self-righteousness, and second because you might – like me – be distrustful of the modern trend for seeking life guidance from business experts. (I note that the co-founder of LinkedIn, the social networking service that pesters me to join it daily, has written a book on "the Silicon Valley approach to building a life" – but if I wanted his advice, I'd send him six unsolicited emails a week requesting it.) Yet to read Christensen's new book, How Will You Measure Your Life?, is to be struck by the solidity of his wisdom. That basketball tale, it turns out, illustrates a powerful principle that really does apply in business and life.
The problem is what Christensen calls "marginal thinking". His favoured corporate example is the US video chain Blockbuster, which proved disastrously non-responsive to the challenge of smaller rivals offering movies by mail. It's not that Blockbuster executives were idiots. It simply made no sense, in terms of marginal costs, to splurge on a new mail-order arm, which would bring smaller profits while cannibalising the firm's main business. Blockbuster had invested millions in its existing setup; marginally speaking, it was far wiser to plough company money into reaping returns from that. Until, one day, it wasn't.
Had Christensen played that basketball game, he'd have been thinking marginally, too: the marginal cost of breaking his rule "just this once" was minor, while the upfront loss of skipping the final was huge. Given his beliefs, though, the eventual cost of compromising his principles would have been larger still. There's always an extenuating circumstance; the cost of "just this once" is always enticingly low. But "life is just one unending stream of extenuating circumstances". Every next step that, say, Nick Leeson or Enron's Jeffrey Skilling took, Christensen points out, was no big deal from a marginal perspective. "The next step," he writes, "is always a small one, and given what you've already done, why stop now?"
Besides, for many people, it's just easier to do things 100% than 98%. That's the approach of Alcoholics Anonymous: once you've decided to stop drinking completely – or never bring work home, or go for a daily run, or keep Sundays basketball-free – you needn't waste time or energy weighing the merits of each potential exception, because there aren't any. "Abstinence is as easy to me as temperance would be difficult," Samuel Johnson said. Hard-and-fast rules can be strangely freeing. Mormons never have to worry if they've had a bit too much coffee.
• The Antidote: Happiness For People Who Can't Stand Positive Thinking, by Oliver Burkeman, is published on June 21, by Canongate Books, at £15. To pre-order a copy for £12, including mainland UK p&p, go to guardianbookshop.co.uk
oliver.burkeman@theguardian.com; twitter.com/oliverburkeman
