In the introduction to the first volume of Democracy in America (1835), Alexis de Tocqueville famously declared that an ‘irresistible revolution’ was sweeping America and would eventually convulse Europe and the world. That powerful movement had been under way for centuries, he believed, and had as its consequence an ever-expanding ‘equality of conditions’, the progress of which was ineluctable, a ‘providential fact’.

Now another French thinker of note, the economist Thomas Piketty, has surveyed the past since the 18th century, along with the present and future, and likewise detected a ‘long-term movement … toward more social, economic, and political equality’ afoot. Piketty, to be sure, sees nothing providential about the process. The ‘movement toward equality is a battle that can be won’, he declares, ‘but it is a battle whose outcome is uncertain’. And whereas Tocqueville regarded this movement with apprehension, observing it with a ‘kind of religious terror’, Piketty embraces it with enthusiasm. His A Brief History of Equality is thus an activist’s history, part reckoning with the past and part manifesto for the future, designed to bolster the courage of those who would continue the forward march.

It is an admirable undertaking, and Piketty, it strikes me at least, is an admirable man. Intellectually generous and wide-ranging in his interests in the way the best French social scientists can be, he is a highly productive and original scholar who has done more than almost anyone alive