21 Lessons for the 21st Century

21 Lessons for the 21st Century is a book by Israeli historian Yuval Noah Harari, published in English in August 2018 and, the same month, in Spanish by the publisher Debate, in a translation by Joandomènec Ros i Aragonès. It is the third volume of a trilogy begun with Sapiens and Homo Deus, but where those works examined humanity's past and future, this one focuses on the present. Several of its twenty-one essays grew out of articles previously published in the press.

The book is organised into five sections. The first, on the technological challenge, argues that liberalism, the dominant story of our time, is in crisis without a successor able to address artificial intelligence and biotechnology. The second deals with the political challenge: nationalism is not enough, and paths toward global cooperation must keep being opened. The third, titled despair and hope, acknowledges the scale of the problems and holds that humanity can still weather them if it keeps its composure and the values of secularism. The fourth concerns truth in a world flooded with disinformation and recommends confronting one's own prejudices and seeking reliable sources. The fifth, on resilience, insists on distinguishing fiction from reality in order to live a full life and to face existential threats.

Its reception was wide. Bill Gates called it fascinating and a contribution to a much-needed global conversation, while other critics, such as John Thornhill in the Financial Times, found it less illuminating than his earlier books and noted that several analyses recycled ideas already aired. Gavin Jacobson, writing in The New Statesman, judged its recommendations too vague to be of real use.