Lecture 2: Judgment Aggregation and Collective Annotation. Judgment aggregation deals with situations where several individuals each make a yes/no choice regarding a number of propositions and these choices then need to be aggregated into a collective choice. Applications range from legal theory to multiagent systems and crowdsourcing. In this lecture we will review a formal framework for judgment aggregation, the doctrinal paradox, a basic impossibility theorem, and the embedding of preference aggregation into judgment aggregation. In the second part of the lecture we will see how to use aggregation rules to process noisy data collected through crowdsourcing and report on a case study with data from computational linguistics.