IF THERE were not a large class of influential people convinced that distributional issues in an economy are not especially important, there would have been no reason for Thomas Piketty to write his book. Its reception across a wide range of thinkers suggests that Mr Piketty's work has enjoyed some success in changing minds. But not everyone is convinced. For those on the fence, it is worth paying attention to the criticism the book has received. Mr Piketty's magnum opus is certainly not without its weaknesses, but the quality of the criticism it has attracted provides a sense of the strength of the argument he makes.

Consider Clive Crook's sceptical review at Bloomberg. He writes:

There's a persistent tension between the limits of the data he presents and the grandiosity of the conclusions he draws.

The line doubles as a pleasingly apt description of Mr Crook's review. He is unhappy at the way Mr Piketty has described the importance of the relationship between r (the rate of return on wealth), g (the growth rate of the economy), and the general significance of capital in an economy. The r>g inequality has been the subject of a lot of discussion, but most sceptics tend to focus on precisely which return or interest rate Mr Piketty has in mind. Mr Crook instead makes the rather remarkable claim that Mr Piketty has not qualified the statement enough. Why, for instance, doesn't Mr Piketty say that r must be significantly above g to generate the expected divergence, Mr Crook complains. This, after literally hundreds of pages in which Mr Piketty has walked through when and how the capital-income ratio has been pushed away from its long-run trend rate. You don't even have to read hundreds of pages to get the qualification Mr Crook wants; you can start with the page on which r>g is first mentioned:

If, moreover, the rate of return on capital remains significantly above the growth rate for an extended period of time (which is more likely when the growth rate is low, though not automatic), then the risk of divergence in the distribution of wealth is very high.

Emphasis mine. I suppose if you only read the book's conclusion you could miss these details, but who would do that? Mr Crook then goes on to present his evidence:

The trouble is, he also shows that capital-to-output ratios in Britain and France in the 18th and 19th centuries, when r exceeded g by very wide margins, were stable, not rising inexorably. The same was true of the share of national income paid to owners of capital. In Britain, the capitalists' share of income was about the same in 1910 as it had been in 1770, according to Piketty's numbers. In France, it was less in 1900 than it had been in 1820.

Mr Piketty is not arguing that r>g means that rising inequality is inevitable. Indeed, that is close to the precise opposite of his argument, which is that r>g is a force for divergence in the economy which has at times been countered by external forces, and which can and should be similarly countered in future. Presumably, if charts of stable capital-income ratios in the 19th century provided a devastating rebuttal to his story, Mr Piketty would not have included them so prominently in the book. I think he must have imagined that readers would look at the text around them as well. He was also good enough to include data on wealth concentrations in the 19th century, which do in fact reveal extraordinary divergence in the distribution of wealth. The wealth share of the rich in France rises steadily over this period, for example; on the eve of the first world war, the top 1% in France control 60% of all wealth.

Mr Crook rather uncharitably questions the motivations of those more taken with the book. He writes:

As I worked through the book, I became preoccupied with another gap: the one between the findings Piketty explains cautiously and statements such as, "The consequences for the long-term dynamics of the wealth distribution are potentially terrifying." Piketty's terror at rising inequality is an important data point for the reader. It has perhaps influenced his judgment and his tendentious reading of his own evidence. It could also explain why the book has been greeted with such erotic intensity: It meets the need for a work of deep research and scholarly respectability which affirms that inequality, as Cassidy remarked, is "a defining issue of our era."

It seems to me that Mr Crook has revealed more about his own priors than those of Mr Piketty's fans. "Terrifying" seems to me to be an accurate description of a society in which the top 10% of individuals own 90% of the wealth. Mr Crook scoffs at this characterisation of inequality, despite the fact that it was in the past associated with a revolution that gave us an episode of political violence known simply as "The Terror".

That brings us to the most important of Mr Crook's criticisms: that it is living standards which actually matter:

Over the course of history, capital accumulation has yielded growth in living standards that people in earlier centuries could not have imagined, let alone predicted -- and it wasn't just the owners of capital who benefited. Future capital accumulation may or may not increase the capital share of output; it may or may not widen inequality. If it does, that's a bad thing, and governments should act. But even if it does, it won't matter as much as whether and how quickly wages and living standards rise. That is, or ought to be, the defining issue of our era, and it's one on which "Capital in the 21st Century" has almost nothing to say.

Even if the book had nothing to say about growth, this would be an odd criticism. "Capital" is not first and foremost a book about the fundamental sources of economic growth. It is also not the great American novel, but that doesn't mean it isn't hugely important.

But in fact, the book speaks directly to Mr Crook's point. Imagine a pre-historic class of political pundit, the members of which firmly believed that the carrying out of winter solstice rituals was absolutely necessary to bring about the return of summer. Then imagine a wise man delivered into the hands of this class a piece of writing containing detailed evidence that there had been many times in the past in which summer had returned even when no rituals had been conducted. Such a work would not constitute a recipe for bringing back the sun, but it would be beyond churlish to say that it contained no information of importance about seasonal dynamics.

Why do we care about inequality? We care about it because we are human, and we can't help but be concerned about matters of fairness, however much economists might wish that were not the case. But what Mr Crook seems not to understand is that we also care about it because we care about living standards. Mr Piketty's book does an able job showing that high levels and concentrations of capital have not been a necessary or sufficient condition for rapid growth in the past, though they have often sowed the seeds for political backlash that is detrimental to long-run growth. His argument is that the living standards of many people around the rich world are now unnecessarily low, because of the nonchalance with which elites have approached distributional issues over the past generation, and that continued heedlessness of this sort will ultimately undermine the growth-boosting institutions of capitalism. His argument is that economic growth that concentrates benefits on a small group of people will probably not be tolerated as fair, even if living standards among the masses are not completely stagnant.

It is an argument that is powerful and well-supported by the data—and extremely relevant today, whether or not one thinks inequality qualifies as the defining issue of the era. That, it seems to me, is why the book has been received as it has.