A plea for the majority method in aggregating judgements

作者：Garcia Bermejo Juan Carlos^*

来源：Journal of Logic and Computation, 2012, 22(6): 1279-1299.

DOI：10.1093/logcom/exr008

• Judgement aggregation
• majority method
• majority voting logical consistency
• collective judgements

The aim of this article is to vindicate the majority method as a procedure that may be suitable for some judgement aggregation problems. The standard literature on judgement aggregation has emphasized that the majority method may fail to meet some restrictions that are considered as binding. For instance, if the number of persons is even, aggregating individual judgements may fail to return a collective judgement. More importantly, using the majority method may lead to a logically inconsistent set of collective judgements. As a consequence, it has been discredited as a suitable judgement aggregation mechanism, while it is known that it meets many attractive properties. In contrast, this article explains how the standard logical consistency restrictions can be weakened in ways that are plausible for some kinds of judgement aggregation problems, in particular when the aggregation aim is of an informational nature rather than using the collective output for decision making. In addition, it is shown that the majority method meets those weak consistency restrictions. Therefore, the article concludes that the use of the majority method can be vindicated at least in addressing such aggregation problems. In order to do so, the article uses a simple variant of the majority method which ranks propositions according to the number of persons that support them, and is closer to the way that the method is used in social choice theory. In addition, it is shown that such a variant satisfies the translation of all the properties that the method meets in that theory, without facing transitivity difficulties such the voting paradox.

• 出版日期2012-12