Thirty years on from the Brixton and Toxteth riots of 1981, England's inner cities are once again disfigured by violence. There are some remarkable similarities to that momentous year: a lavish royal wedding, an austerity budget and high youth unemployment. This time, as then, the trigger for the unrest was an allegation of police brutality. The Metropolitan Police has improved significantly since the 1980s but its response to the shooting of Mark Duggan in Tottenham by its Operation Trident team was inept. It was wrong that Mr Duggan's family had to wait 36 hours to see his body and that confusion over whether the suspect had fired at police was allowed to spread.
There are important differences from the events of 1981. In the words of Lord Scarman's report into the upheavals in Brixton, those riots were "an outburst of anger and resentment by young black people against the police". The terrifying speed with which the violence spread from London to other big cities this time was suggestive of a far more complex and profound sense of social alienation.
Some of these discrepancies reflect a technological shift. The growth of social networks such as Twitter and mobile platforms such as BlackBerry Messenger has allowed riots to be co-ordinated at a speed that has left the police, by their own admission, "stretched beyond belief". Yet the medium should not be confused with the motive.
Returning from his holiday, David Cameron described the behaviour of the youths as "criminality, pure and simple". The analytical moment seems to have been postponed indefinitely. While the Prime Minister's desire not to be seen to "explain away" the riots was understandable, he must eventually offer the sort of thoughtful response of which he is capable. In 2006, in what became known as his "hug a hoodie" speech, the then leader of the opposition declared: "The first thing is to recognise that we'll never get the answers right unless we understand what's gone wrong. Understanding the background, the reasons, the causes. It doesn't mean excusing crime but it will help us tackle it." He was talking about antisocial behaviour but he could have been talking about this month's riots.
If the left is to create the intellectual space for such a debate, it must be far clearer about what those causes were. The riots were not, as some have claimed, an uprising or insurrection against the coalition's spending cuts. Many of the cuts deemed responsible for the violence have not even taken effect. This is not to say that the cuts will not make matters worse. Rather, it is to say that placing an undue and politically convenient emphasis on their role risks masking the social and economic deformities that lie beneath the violence.
Britain's disturbed and profoundly unequal society is one in which many feel they have no stake. Youth crime is a problem for all developed countries but, as Richard Wilkinson and Kate Pickett point out in their survey of inequality, The Spirit Level, the problem is worst in those societies in which the gap between rich and poor is greatest.
The looting was, on one level, pure nihilism; on another, it was a crude attempt by rioters to mimic the conspicuous consumption exercised by the affluent and credit-rich. It was an expression of the values of a society in which we have been taught that, in the words of the former Labour minister Alan Milburn, to lead a good life is to "earn and to own".
Labour and the wider left must pay greater attention to those cultural factors - most notably family breakdown - that they have too often downplayed. All of our politicians need to think deeply about how the urban poor have been disenfranchised by globalisation; how our culture has been coarsened and debased by lifestyle libertarianism.
If the Prime Minister still believes in tackling the causes of youth disorder, and not just the symptoms, he must now lead the thoughtful debate that the recent disturbances demand.