Thomas Piketty put inequality in the advanced market economies at the heart of political debate. The French economist’s 2013 bestseller Capital in the 21st Century used long runs of historical data on incomes and wealth to demonstrate how wide the gap between the rich and the rest has become. Thick with data and the famous “r>g” formula, it was published after a decade or more of median incomes stagnating, validating righteous outrage about the chasms scarring early 21st-century society.

It was a rather gloomy book, arguing in effect that as “r” — the rate of return on capital — usually is greater than “g” — the growth rate of the economy and hence labour incomes, it takes a cataclysm to reduce inequality. War, destroying the value of the assets held by the rentier classes, is generally required.

That underlying pessimism is also present in this new book, A Brief History of Equality. “[T]he most fundamental transformations seen in the history of inegalitarian regimes involve social conflicts and large-scale political crises,” Piketty writes, referring to the French Revolution and the two world wars: the assets of the wealth are destroyed and, alongside this levelling down, crises generate a more egalitarian sentiment, at least for a while.

Yet there is an unexpected seam of optimism too — reflected in the choice of the word “equality” in the book’s title, running counter to the Piketty-the-pessimist brand. This is not because we are currently experiencing pestilence and war (the book was written before the Russian attack on Ukraine). Rather, it is because Piketty focuses instead on the promise of socialism to reduce inequalities. The book advocates for positive political change — though it does not map out any practicalities of how such positive change might be achieved.

Rather, social struggles, labour movements and taxes in the mid-20th century are highlighted. “We have to deepen and generalize the institutions that made the movement toward equality, human progress, and prosperity possible . . . starting with the welfare state and progressive taxation,” writes Piketty. These institutions include unions to fight for higher earnings, redistribution through progressive taxes and generous benefits, and universal public services.

The author envisions “a democratic and federal socialism, decentralized and participatory, ecological and multicultural”. Thanks to the revival of the political debate about redistribution and justice, we will have power-sharing in business, reparations for colonialism and slavery, and will have driven the influence of money out of politics and the media, according to this extraordinarily rose-tinted agenda.

The tension between the pessimistic and optimistic Pikettys runs through A Brief History. It condenses the 3,000 pages of his previous books (Top Incomes in France in the 20th Century, Capital in the 21st Century and Capital and Ideology) into 250 pages, with a greater focus on the global political perspective of the last of these than on the long-run economic trends of the first two.

The sins of empire feature prominently, from the horror of the slave trade to the protection of the imperial centre’s markets and extraction of colonial resources. It is a unidimensional history: exploitation is the only reason for the rise of the west, and that other dimensions exist is not even mentioned. Indeed, the end of empire is introduced as a key explanatory factor for the “Great Redistribution” that occurred between 1914 and 1980. While world wars and the Depression paved the way for subsequent social struggles internal to the west, the liquidation of foreign and colonial assets “helped to reduce inequalities and destroy perceptions of private property as sacred”.

A Brief History of Equality is a route into Piketty’s arguments in his earlier books, with their luxuriantly extensive data and historical detail. Anybody who has not been able to face those tomes (the third so bulky it came with its own sturdy canvas tote bag) should read this one. But it will probably be less influential. Although economists nitpicked holes in the theory and data of Capital in the 21st Century, and while historians challenged the, well, ideological interpretations of global history in Capital and Ideology, the huge mass of detail in those earlier volumes was the source of their rhetorical impact in the inequality debate. There was no need for most people to read them cover to cover — and they did not; it was enough to know that their argument rested on so many pages of evidence.

Strip away the detail and what remains is an all-too-apparent underlying abstraction from the practical politics of change, an abstraction emphasised by the book’s very literal translation by Steven Rendall from intellectual French. If “r” really is greater than “g”, then perhaps inequality does have its own internal dynamics, but achieving a turn to “democratic, decentralized socialism” surely demands some attention to how it might come about?

The issue is that Piketty’s theory of change is motivated by ideology, so articulating a persuasive alternative ideology is enough. And surely a vision of a fair, green, participatory future is persuasive enough? Sadly, what convinces readers in the salon differs from what drives action on the streets, or even in the corridors of power, where Pessimistic Piketty is likely to prove more persuasive than this newly Optimistic Piketty.

A Brief History of Equality by Thomas Piketty, translated by Steven Rendall, Belknap (Harvard) £22.95, 288 pages

Diane Coyle is professor of public policy at the University of Cambridge

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