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...

This review article introduces and evaluates various ways to aggregate probabilistic opinions of different individuals. For each of these three ways, an axiomatic characterization result is presented (a new one in the case of multiplicative pooling). The three ways satisfy different axioms and...