Published online by Cambridge University Press: 08 September 2015
In Democratic Reason, Hélène Landemore has built a case for the epistemic virtues of inclusive deliberative democracy based on the cognitive diversity of the group engaged in making collective decisions. She supports her thesis by appealing to the Diversity Trumps Ability Theorem of Lu Hong and Scott Page. This theorem is quite technical and the informal statements of it aimed at democratic theorists are inaccurate, which has resulted in some misguided critiques of the theorem's applicability to democratic politics. This paper provides an exposition of the Diversity Trumps Ability Theorem that does not sacrifice precision for accessibility. It also shows that it is not possible to satisfy the assumptions of this theorem when there are only two options. Thus, the Diversity Trumps Ability Theorem cannot provide support for the epistemic virtues of inclusive democratic deliberation for binary collective decisions.