Wesley Buckwalter

We accomplish three things in this paper. First, we provide evidence that the motivational internalism/externalism debate in moral psychology could be a false dichotomy born of ambiguity. Second, we provide further evidence for a crucial distinction between two different categories of belief in folk psychology: thick belief and thin belief. Third, we demonstrate how careful attention to deep features of folk psychology can help diagnose and defuse seemingly intractable philosophical disagreement in metaethics.

People suffering from severe monothematic delusions, such as Capgras, Fregoli, or Cotard patients, regularly assert extraordinary and unlikely things. For example, some say that their loved ones have been replaced by impostors. A popular view in philosophy and cognitive science is that such monothematic delusions aren't beliefs because they don't guide behaviour and affect in the way that beliefs do. Or, if they are beliefs, they are somehow anomalous, atypical, or marginal beliefs. We present evidence from five studies that folk psychology unambiguously views monothematic delusions as stereotypical beliefs. This calls into question widespread assumptions in the professional literature about belief's stereotypical functional profile. We also show that folk psychology views delusional patients as holding contradictory beliefs. And we show that frequent assertion is a powerful cue to belief ascription, more powerful than even a robust and consistent track record of non-verbal behaviour.

We distinguish between two categories of belief—thin belief and thick belief—and provide evidence that they approximate genuinely distinct categories within folk psychology. We use the distinction to make informative predictions about how laypeople view the relationship between knowledge and belief. More specifically, we show that if the distinction is genuine, then we can make sense of otherwise extremely puzzling recent experimental findings on the entailment thesis (i.e. the widely held philosophical thesis that knowledge entails belief). We also suggest that the distinction can be applied to debates in the philosophy of mind and metaethics.

Recently psychologists and experimental philosophers have reported findings showing that in some cases ordinary people's moral intuitions are affected by factors of dubious relevance to the truth of the content of the intuition. Some defend the use of intuition as evidence in ethics by arguing that philosophers are the experts in this area, and philosophers' moral intuitions are both different from those of ordinary people and more reliable. We conducted two experiments indicating that philosophers and non-philosophers do indeed sometimes have different moral intuitions, but challenging the notion that philosophers have better or more reliable intuitions.