The comparative method is a time-honored method of inquiry that focuses on analysis of similarities and differences between two or more objects. The ancient Greek philosopher Aristotle ( 384–22 BCE ) used the comparative method to study a variety of polities in the Greek world and build a theory from his observations about the nature of politics and good government.
At the broadest level all modes of scientific inquiry require some form of comparison; it is difficult to make judgments about a particular without a reference point. The nineteenth-century British philosopher John Stuart Mill ( 1806–73 ) developed a system of logical reasoning by distinguishing two methods of inquiry—the method of agreement and the method of difference. Scholars use comparison in inductive reasoning when they draw generalizations by observing, classifying, and comparing particular cases. They also use comparison in deductive reasoning when they test hypotheses or apply general principles in the world of particular cases.
Comparison figures into the various modes of scientific inquiry. The experimental and quasi-experimental methods use comparison when they test for similarities and differences between a treatment group and a control group; comparison is part of broad statistical analysis involving a large number of cases; and comparison even finds its way into the case-study approach in which observers focus on one specific case to get a better sense of its nuances and complexities.
The political scientist Arend Lijphart, however, argued for a narrower meaning of the comparative method. By his definition the comparative method in political science has come to refer to the method of “the small n” in which “n” refers to the number of cases studied ( Lijphart 1971 ). In this sense the comparative method is used to study questions that are best addressed less by statistical analysis of a large number of cases or by case-study analysis of one case than by the study of a few cases that share in common some medium-range topic, such as models of political revolution or types of local government reform. When used in this way, as an intermediate form of analysis, the comparative method can draw on the strengths of both the breadth of statistical analysis and the focus of casestudy analysis.
The comparative method is an indispensable tool of interpretation, perspective taking, and accounting for different points of view. These may involve cross-cultural comparisons across or within nations. Comparativists argue that even a topic such as American exceptionalism requires comparison to understand how America is and is not unique. The dangers of crosscultural comparisons are twofold: ethnocentrism, in which observers cannot get past their own culture in viewing others; and cultural relativism, in which observers sublimate their own culture and can become apologists for moral wrongs such as slavery because those wrongs were generally accepted as right in a certain culture or period. The classic applications of the interpretive use of comparison in studying American history remain best captured in C. Vann Woodward's collection of lectures, The Comparative Approach to American History ( 1968, 1997 ).
Hirschl, Ran. Comparative Matters: The Renaissance of Comparative Constitutional Law. Oxford, UK: Oxford University Press, 2014.
Lijphart, Arend. “Comparative Politics and the Comparative Method.” American Political Science Review 65, no. 3 (1971): 682–93.
Woodward, C. Vann, ed. The Comparative Approach to American History.(1968.) New York: Oxford University Press, 1997.
Russell Sage College