The dazzling achievements of the natural sciences have exerted an enormous pressure on the social sciences to model themselves on the former. Positivists believe that we should study the natural and social worlds in the same way. Initially, in the nineteenth century, positivists wanted to exclude appeals to supernatural causes. They argued that humans were part of nature, and so open to empirical study using a scientific method based on the rigorous collection and sifting of facts. Later, by the middle of the twentieth century, positivists began to argue that the social sciences should search for causal and predictive explanations akin to those in the natural sciences (Ayer, 1967; Hempel, 1942). This positivism suggests that the social sciences study fixed objects with observable and, to some extent, measurable properties. Social scientists explain these objects by general laws, albeit general laws that assign probabilities to different outcomes.