The first edition of this work was an extension of a much shorter book, Nuts and Bolts for the Social Sciences. By and large, the extension was in breadth, not in depth. Many more topics were covered, but at more or less the same level of analysis. This revised edition covers roughly the same topics as the first, but provides, I hope, greater insight.

To make room for the substantial amount of new material, while keeping the book within a manageable size, Part IV – “Lessons from the natural sciences” – has been eliminated. Some discussions in that Part have been incorporated into the new Chapter 11, “Reinforcement and selection,” and Chapter 20. A new chapter on “Transmutations” is added. The chapters in Part V on collective belief formation, collective action, collective decision making, institutions and constitutions, as well as the Conclusion, are entirely rewritten. Most chapters in Part II are also substantially modified. Parts I and III are also revised, but less heavily.

The revisions and additions draw on five books I have published in the meantime: Agir contre soi (2007), Le désintéressemen t (2009), Alexis de Tocqueville: The First Social Scientist (2009), L–irrationalité (2010), and Securities Against Misrule (2013). They also reflect a deeper immersion in Seneca, Tocqueville, Bentham, and Proust, as well as a belated first reading of The Theory of Moral Sentiments, Hume's History of England, and Gibbon–s Decline and Fall of the Roman Empire. A number of books on the American war in Vietnam opened my eyes to the importance of stupidity, however intelligent, in human affairs.

In revising the book, I have given free rein to associations and digressions. My role models in this respect are Montaigne's Essays, The Psychology of Interpersonal Relations by Fritz Heider, The Strategy of Conflict by Thomas Schelling, and The New Rhetoric by Chaim Perelman and Lucie-Olbrechts-Tyteca. However different in substance, these books have in common a playful obsession with revealing details, even seemingly trivial ones, superimposed on the analytical structure.