Quantification is one way of employing the scientific method to discover things about the world. In the social sciences we are trying to discover things about the social world, but the approach we use can still be regarded as scientific. The scientific approach attempts to abstract from the nuances and details of a story the salient features that can be built up into a theoretical statement (or statements) expected to hold true of any situation that can be defined in terms of the same abstractions. If such a theoretical statement does not hold true in some specific situation, this is presumed to be either because the theory was wrong or because it was not sufficiently elaborated. Elaborating social theories to bring in additional features of the world, found necessary for a full explanation, is an important feature of the scientific approach; but for elaboration to progress very far we need to employ quantitative analysis, as this chapter will try to show.

The transition from case studies to quantitative analysis is largely a matter of the number of cases. If you have one case, no causal inferences can be made. If you have two cases, you can rule out something as a necessary condition for something else. If you have three cases you can rule out two things, or you can start to make quantitative statements (for example, something might be found to pertain two-thirds of the time).