Britain has experienced two crises this August, one on the streets and one in the markets. The French philosopher Jean-Jacques Rousseau perceived the common issue three centuries ago. The gangs he observed were not on the city streets or trading floors, they were huntsmen: “If a deer was to be taken, everyone saw that, in order to succeed, he must abide faithfully by his post: but if a hare happened to come within the reach of any one of them, it is not to be doubted that he pursued it without scruple and, having seized his prey, cared very little, if by so doing he caused his companions to miss theirs.”

Rousseau was an early and incisive critic of the idea that self-interested behaviour would necessarily work to the benefit of all. If the hunt were to catch a deer, it would need to establish shared values and probably impose them through some sort of hierarchy. Without such a structure there would be no more for supper than the occasional hare. It is unlikely that the people who introduced the concept of “eat what you kill” into modern professional services had read Rousseau. Nor – it is safe to say – had the people who snatched electrical goods from the broken shop windows of Tottenham.

Two broad economic theories describe the allocation of income and wealth. The power theory states, broadly, that people get what they grab: from the forest, the markets, or the shop window. The distribution of income reflects the distribution of power. For most of history, this was plainly true – the landlord took what he could from the tenant, the baron what he could from the landlord and the king what he could from everyone. The sixth Duke of Muck was rich because the first Duke of Muck had been an especially successful gang leader. The alternative theory is that what people earn reflects their marginal productivity – how much they personally add to the value of goods and services. The marginal productivity theory has many attractions, especially to those who are well paid: if what they receive is a product of their own efforts, their rewards are surely well deserved.