Imagine an elected official, Ofra, who emphasizes the importance of campaign finance reform legislation in all of her speeches. She commands all the relevant facts of the proposed legislation, and can explain exactly how she thinks it will offer much needed protections against inappropriate corporate interference in governance. But when the opportunity arises, Ofra abstains from casting the deciding vote that would pass the bill into law. So does Ofra believe that the reform legislation is important?
On the one hand, given her command of the facts, it seems that on at least some level Ofra thinks that the reform legislation is important. On some level she accepts that the proposition <the reform legislation is important> is true. On the other hand, when given the opportunity, she doesn’t vote the bill into law, which makes it seem that she doesn’t believe that the legislation is important. It's almost like on a purely intellectual level, Ofra believes the proposition, whereas on a more practical level, she doesn’t.
In a new [paper], David Rose, John Turri, and I argue that the ambivalence we feel about Ofra reflects implicit competence with two related but distinct folk psychological concepts, each of which often finds expression with ‘belief’. We call these divergent senses thin belief and thick belief. On our view, a thin belief is a bare cognitive pro-attitude. Thinly believing P involves representing that P is true, regarding it as true, or taking it to be true. However a thick belief requires more than a bare cognitive pro-attitude. On first approximation, thick belief also involves emotion or conation. For example, in addition to representing and storing P as information, you might also like it that P is true, emotionally endorse the truth of P, explicitly avow or assent to the truth of P, or even actively promote an agenda that makes sense given P.
We suggest that thin and thick beliefs approximate genuine and genuinely distinct categories within folk psychology, and can be used to make informative predictions about how people view the relationship between knowledge and belief. Specifically, our main focus in the paper is to show that if the distinction is genuine, then we can make sense of otherwise extremely puzzling findings in recent experimental philosophy [here], [here] and [here] questioning the entailment thesis (i.e. the widely held philosophical thesis that knowledge entails belief). We argue that the entailment thesis should be understood in terms of thin belief. And as it turns out, when people are primed to employ the concept of thin belief, they respond exactly as we would expect if belief entailment was widely accepted.