Ethical philosophy isn't the most scintillating of subjects, but it has its moments. Take, for example, the work of the US philosopher Eric Schwitzgebel, who's spent a large chunk of his career confirming the entertaining finding that ethicists aren't very ethical. Ethics books, it turns out, are more likely to be stolen from libraries than other philosophy books. Ethics professors are more likely to believe that eating animals is wrong, but no less likely to eat meat. They're also more likely to say giving to charity is a moral obligation, but they were less likely than other philosophers to return a questionnaire when researchers promised to donate to charity if they did. Back when the American Philosophical Association charged for some meetings using an honesty system, ethicists were no less likely to freeload.

One take on this is that ethicists are terrible hypocrites. As Schwitzgebel points out, that's not necessarily as bad as it sounds: if philosophers were obliged to live by their findings, that might exert a "distortive pressure" on their work, tempting them to reach more self-indulgent conclusions about the moral life. (And there's a case to be made, after all, that it's better for people to preach the right thing but not practise it than to do neither.) But another possibility bears thinking about. It's plausible to suggest that ethicists have an unusually strong sense of what's right and wrong; that's what they spend their days pondering, after all. What if their overdeveloped sense of morality – their confidence that they know what's what, ethically speaking – makes them less likely to act ethically in real life?

This would be an intriguing twist on "moral licensing", the deep-seated human tendency that leaves us feeling entitled to do something bad because we've already done something good. It explains why people give up plastic bags, then feel justified in taking a long-haul flight, obliterating the carbon savings. It's also why, if you give people a chance to condemn sexist statements, they'll subsequently be more likely to favour hiring a man in a male-dominated profession. Could it be that merely doing the mental work of figuring out what's right ticks an internal "morality" box, so licensing "moral" people to act as badly as anyone else? (Or worse: remember those library books.) This is speculation, but if it's right, the implications would reach beyond philosophers. Smugness might not just be annoying to others; it could actively make smug people less moral.

The broader peril here – that we might fail to do what we ought to do because we know we ought to do it – threatens to undermine personal happiness, too. Consider this extreme example: about a decade ago, the multimillionaire banker Rajat Gupta gave a speech about the dangers of becoming super-rich. "You have to watch out for it," he said. "Because the more you have, the more you get used to comforts [and] big houses and vacation homes, and going and doing whatever you want. So it is very seductive." He knew the unrestrained pursuit of material wealth wasn't the path to happiness. But last year Gupta was convicted of conspiracy and fraud in the Galleon hedge fund case, the biggest insider trading scandal in US history. You can't really say he should have known better: clearly he did. Was it his confidence in his knowledge that caused him to forget himself? Was knowing better the problem?

oliver.burkeman@theguardian.com

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