Judgment aggregation theory is a new aggregative theory that differs from the antecedent theory of social choice by having the collective rule bear on judgments rather than preferences or utilities. It represents judgments, both individual and collective, in terms of a formalism borrowed from elementary logic, hence its alternative labelling as logical aggregation theory. It originates in a classic court example due to Kornhauser and Sager (1992), the doctrinal paradox, and the present lecture will be geared at further clarifying this example by means of the new theory, following the lines of recent work by Dietrich and Mongin (2010) and Mongin (2012). After elaborating on the doctrinal paradox, the lecture will expand on legal applications more generally.