A long time ago, I happened upon a cartoon in some publication or other. A single frame—in the vein of Gary Larson—depicted thousands of sheep rushing headlong off a cliff. In the middle of this great multitude, one particular sheep moved in the opposite direction. “Excuse me…excuse me…excuse me,” it bleated. That scene came to mind recently as I read Douglas Murray’s latest book. He takes his title and inspiration from Extraordinary Popular Delusions and the Madness of Crowds (1841), that oddly compelling 19th-century miscellany by Charles Mackay, a book that is still in print and widely read today. This is because it concerns the most bestial part of human nature: the herd mentality.