The Two-party System and Duverger's Law: An Essay on the History of Political Science

Abstract

Science involves the accumulation of knowledge, which means not only the formulation of new sentences about discoveries but also the reformulation of empirically falsified or theoretically discredited old sentences. Science has therefore a history that is mainly a chronicle and interpretation of a series of reformulations. It is often asserted that political science has no history. Although this assertion is perhaps motivated by a desire to identify politics with belles lettres, it may also have a reasonable foundation, in that political institutions may change faster than knowledge can be accumulated. To investigate whether propositions about evanescent institutions can be scientifically falsified and reformulated, I examine in this essay the history of the recent and not wholly accepted revisions of the propositions collectively called Duverger's law: that the plurality rule for selecting the winner of elections favors the two-party system. The body of the essay presents the discovery, revision, testing, and reformulation of sentences in this series in order to demonstrate that in at least one instance in political science, knowledge has been accumulated and a history exists.