We live in an information network and in an exchange of opinions that is ubiquitous and constant – a net of epistemic acts that we exchange with other agents and affect what we end up believing and deciding. Working with information implies more and more that we face the social effects of this – and these are today faster and faster, and we get a glimpse of them in real time. However, the more agents we have involved, the harder to understand the dynamics of information release turn to be.

This course introduces a formal toolkit that helps in this enterprise.
In particular, the course aims at securing: (1) the understanding of the problems of reasoning that can be triggered by the release of information; (2) the understanding of models that capture the dynamic effects of information release, and the conceptual problems they raise; (3) the problems connected to the representation of belief-merging and, in general, the relations between individual and collective notions of epistemic attitudes;
(4) the understanding of the conditions at which consensus is possible, the role it can play, and the relation between the information release policies, the connection of the epistemic network, and the hierarchies and trust distribution in epistemic communities.

(3) e (4) presuppose (1) and (2). In turn, the last two objectives come with a view on the social impact that the information release policies have on a community of epistemic agents. The course employs a varied package of methods and tools, especially those from Epistemic Logic and Dynamic Epistemic Logic, but also, to a lesser extent, notions and methods from Judgement Aggregation and Network Epistemology, which the course will briefly introduce.

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The course discusses the problems that motivated Judgment Aggregation Theory, and how the latter reacts to such problems. In particular, we will discuss the problems connected to the majority rule, the formal intepretation of the aggregation from individual to collective opinions envisaged by Judgment Aggregation Theory, and a list of conditions that are traditionally deemed desirable for aggregation rules. We will then explore the impossibility results showing that, at given conditions, an aggregation rule satisfying some given bundles of desirable conditions cannot but collapse on dictatorship or oligarchies. We will then explore the attempts at circumventing the collapse implied by the impossibility results by a convenient redesign of the desirable conditions. The course is taught in English.

Core Documentation

Grossi D. e Pigozzi G., Judgment Aggregation: a Primer, Morgan & Claypool Publishers, Kentfield, CA, 2013.

Type of delivery of the course

Lectures. Participation of students will be required in different occasions during classes. When possible, the lectures will start by discussing examples and specific problems. Participation is required especially in these occasions. The class will be taught in English. In case the medical emergency connected with COVID-19 is extended or reinstated, the possible dispositions governing teaching activities will be adopted.

Type of evaluation

There will a written exam after the course ends. Valuation will consider and depend on: 1) Knowledge of the conceptual contents presented through the lectures; 2) The mastery of the problems of Judgment Aggregation Theory through the discussion of specific problems; 3) The ability of answering in a clear and precise way. In case the medical emergency connected with COVID-19 is extended or reinstated, the possible dispositions governing teaching activities will be adopted.