In what follows I discuss and (hopefully) render harmless a doctrine which has a very long ancestry, has constantly reappeared in the history of sociology and still appears to haunt the scene. It was, we might say, conceived by Hobbes, who held that "it is necessary that we know the things that are to be compounded before we can know the whole compound' for "everything is best understood by its constitutive causes', the causes of the social compound residing in "men as if but even now sprung out of the earth, and suddenly, like mushrooms, come to full maturity, without all kinds of engagement to each other'.' It was begat by the thinkers of the Enlightenment, among whom, with a few important exceptions (such as Vico and Montesquieu) an individualist mode of explanation became pre-eminent, though with wide divergences as to what was included, in the characterisation of the explanatory elements. It was confronted by a wide range of thinkers in the early nineteenth century, who brought to the understanding of social life a new perspective, in which collective phenomena were accorded priority in explanation.