The Epistemic Core of Plausibility

Kiel Brennan-Marquez, Yale Law School

Abstract

By instituting a new benchmark of pleading—plausibility—Iqbal and Twombly have left an indelible mark on federal procedure. This article examines plausibility’s substantive origins in order to theorize its epistemic core. The central claim is that determinations of plausibility stem from a dual epistemology: legal knowledge combined with non-legal knowledge. To deem something plausible is to determine not only that it is cogent as a matter of law, but also that it is likely as a matter of practice. The latter requires extrapolating from a theory of “how the world works,” a synergy of experience and expertise. In reasoning about plausibility, judges draw on their own experiences in the world, but also on the wisdom of experts. Equipped with this definition of plausibility, the article closes by comparing Justice Souter’s use of plausibility analysis in Twombly to Justice Kennedy’s use of the same in Iqbal. It argues that Twombly thoughtfully incorporated expert knowledge into antitrust pleading, while Iqbal relied on unfounded “common sense” to draw shaky conclusions about matters of significant normative dispute. Iqbal, therefore, should be taken as far more controversial than Twombly.