Alan Macfarlane is a distinguished British social anthropologist, celebrated for giving that discipline an historical turn. He is the author of important books claiming that the English had become “individualist”—in familial matters as much as in economic life—in the late Middle Ages. This view had the mixed blessing of an endorsement by Sir Keith Joseph, the intellectual powerhouse of early Thatcherism, thereby making Macfarlane a decidedly controversial figure. The present book draws on these early views, but is very much the product of sustained interaction with the thought of the late Ernest Gellner (who spent most of the last years of his life at Cambridge chairing the department in which Macfarlane teaches). What we are offered in this book then is a summary of a particular line of argument, drawing on philosophy and anthropology, which speaks to the interests of economic historians in a slightly abstract but decidedly high-powered manner. The presupposition of the whole is stated in the title, albeit that the “riddle” is in fact twofold. One riddle is the blocking of sustained development: given human ingenuity and obvious early development, why was it that most agrarian civilizations eventually hit some sort of ceiling? The second conundrum then concerns the fundamental breakthrough to capitalist and industrial modernity.