I propose a new axiom on the aggregation of individual yes/no judgments on propositions into collective judgments: each collective judgment depends only on people's judgments on 'relevant' propositions. This contrasts with classical independence: each collective judgment depends only on people's...

Behaviourism is the view that preferences, beliefs, and other mental states in social-scienti�c theories are auxiliary constructs re-describing people's behav- ioural dispositions. Mentalism is the view that they capture real phenomena, no less existent than the unobservable entities and...

We introduce a “reason-based” way of rationalizing an agent’s choice behaviour, which explains choices by specifying which properties of the options or choice context the agent cares about (the “motivationally salient properties”) and how he or she cares about these properties (the...

It is often claimed that opinions are more likely to be correct if they are held independently by many individuals. But what does it mean to hold independent opinions? To clarify this condition, we distinguish four notions of probabilistic opinion independence. Which notion applies depends on...

The contemporary theory of epistemic democracy often draws on the Condorcet Jury Theorem to formally justify the `wisdom of crowds'. But this theorem is inapplicable in its current form, since one of its premises -- voter independence -- is notoriously violated. This premise carries...

How can different individuals' probability assignments to some events be aggregated into a collective probability assignment? Classic results on this problem assume that the set of relevant events -- the agenda -- is a σ-algebra and is thus closed under disjunction (union) and conjunction...

This paper characterizes different belief revision rules in a unified framework: Bayesian revision upon learning some event, Jeffrey revision upon learning new probabilities of some events, Adams revision upon learning some new conditional probabilities, and `dual-Jeffrey' revision upon learning...

What is the relationship between degrees of belief and (all-or-nothing) beliefs? Can the latter be expressed as a function of the former, without running into paradoxes? We reassess this “belief-binarization” problem from the perspective of judgmentaggregation theory. Although some...

How can different individuals' probability functions on a given σ-algebra of events be aggregated into a collective probability function? Classic approaches to this problem often require `event-wise independence': the collective probability for each event should depend only on the individuals'...

When individual judgments ('yes' or 'no') on some propositions are aggregated into collective judgments, the agenda setter can sometimes reverse a collective judgment by changing the set of propositions under consideration (the agenda). I define different kinds of agenda manipulation, and...