Thomas Piketty, the French economist whose earlier work Capital in the Twenty-First Century documented the dynamics of wealth concentration, here offers a more accessible and optimistic account of the historical movement toward equality. Piketty argues that over the centuries, societies have made genuine progress in reducing inequality through political struggle and institutional innovation, from the abolition of slavery to progressive taxation to the expansion of education. This book synthesizes decades of research into global wealth and income data while making the case that greater equality is both possible and desirable. Piketty examines the specific policies and social movements that have produced more egalitarian outcomes, including labor organizing, suffrage expansion, and the construction of welfare states. He challenges both the conservative view that inequality is natural or beneficial and the pessimistic left-wing view that nothing ever really changes. At the same time, Piketty documents the reversals of the past four decades and the ideological developments that enabled them, calling for renewed commitment to democratic socialism. The book's recommendations include wealth taxes, inheritance reform, and what Piketty calls 'participatory socialism' involving worker representation in corporate governance. More hopeful than his earlier work, this book provides both historical evidence and policy proposals for those who believe a more equal world is achievable.