The notion that civility is on the decline is a perennial one. If the BBC website’s Have Your Say slot had existed in Tudor England, you can be sure “Mike from London” would have used it to rail against insolent costermongers and youths playing their lutes too loudly. The thesis has been challenged – a report last year from the Young Foundation argued that civility is thriving, especially in disadvantaged areas – but the perception seems unshakable: one survey, in 2009, found that 90% of Britons believed manners were getting worse. Still, whatever the facts, we can all agree it would be bad if true. Or can we? After reading the philosopher Emrys Westacott’s book, The Virtues Of Our Vices – subtitled A Modest Defence Of Gossip, Rudeness, And Other Bad Habits – I’m less sure. He claims rudeness isn’t all bad; and before telling him to shut his face, we should politely consider his argument.

Our debates about civility are undeniably odd. Have you noticed, for example, how those who complain most about declining manners are enraged by “political correctness”? Set aside the fact that PC is largely imaginary, an emission of foul mind-gas from the brain of Richard Littlejohn. Even if it weren’t, it would be a case of too much politeness towards others, not too little. Also: is rudeness based on obliviousness the same as rudeness based on contempt? And so on. Maybe we need a philosopher, after all.

The idea of applying philosophy to everyday life has been back in fashion for a while, but as Westacott points out, it isn’t always as practical as it purports to be. Bringing Heidegger to bear on your views on the death penalty isn’t of practical use most days. And while thought experiments like the one about pushing a fat man off a bridge are a staple of “practical ethics”, here’s hoping you never face that dilemma. Westacott focuses instead on “microethics”, the philosophical conundrums we encounter hourly. “Precisely because rudeness is quite common,” he writes, “it is not a trivial issue… in our day-to-day lives it is possibly responsible for more pain than any other moral failing.”

At the core of rudeness, Westacott argues, is the violation of social convention, which leads to a crucial distinction – between violating (out of selfishness) a convention to which one otherwise subscribes, versus simply not subscribing to it. We tend to assume most rudeness belongs to the former category. But conventions change, and “rudeness” may often just be the label we give to the friction between two people following different rules. When sons started abandoning the convention of calling their fathers “Sir”, it was presumably perceived as rude. It’s disconcerting to realise that “music in train carriages ought not to be audible to others” might prove just as historically contingent.

“The problem is not that people today are trampling underfoot the time-honoured rules of polite behaviour; the problem is that these rules are in flux,” Westacott writes. Rudeness is the price we pay for “living in a dynamic culture”. That may not make it good, exactly, but it makes it an inevitable by-product of something many of us think of as good. Maybe that explains why critics of PC also bemoan the rise of rudeness: both complaints are reactions against change. A world with no rudeness, and no material for stories about “PC gone mad”, would be one that had come to a standstill.