Sarah-Jane Leslie

Higginbotham argues that conditionals embedded under quantifiers constitute a counterexample to the thesis that natural language is semantically compositional. More recently, Higginbotham and von Fintel and Iatridou have suggested that compositionality can be upheld, but only if we assume the validity of the principle of Conditional Excluded Middle. I argue that these authors’ proposals deliver unsatisfactory results for conditionals that, at least intuitively, do not appear to obey Conditional Excluded Middle. Further, there is no natural way to extend their accounts to conditionals containing ‘unless’. I propose instead an account that takes both ‘if’ and ‘unless’ statements to restrict the quantifiers in whose scope they occur, while also contributing a covert modal element to the semantics. In providing this account, I also offer a semantics for unquantified statements containing ‘unless’

Psychological essentialism is the belief that some internal, unseen essence or force determines the common outward appearances and behaviors of category members. We investigated whether reasoning about transplants of bodily elements showed evidence of essentialist thinking. Both Americans and Indians endorsed the possibility of transplants conferring donors' personality, behavior, and luck on recipients, consistent with essentialism. Respondents also endorsed essentialist effects even when denying that transplants would change a recipient's category membership (e.g., predicting that a recipient of a pig's heart would act more pig-like but denying that the recipient would become a pig). This finding runs counter to predictions from the strongest version of the “minimalist” position (Strevens,2000), an alternative to essentialism. Finally, studies asking about a broader range of donor-to-recipient transfers indicated that Indians essentialized more types of transfers than Americans, but neither sample essentialized monetary transfer. This suggests that results from bodily transplant conditions reflect genuine essentialism rather than broader magical thinking

Generic sentences (e.g., bare plural sentences such as “dogs have four legs” and “mosquitoes carry malaria”) are used to talk about kinds of things. Three experiments investigated the conceptual foundations of generics as well as claims within the formal semantic approaches to generics concerning the roles of prevalence, cue validity and normalcy in licensing generics. Two classes of generic sentences that pose challenges to both the conceptually based and formal semantic approaches to generics were investigated. Striking property generics (e.g. “sharks bite swimmers”) are true even though only a tiny minority of instances have the property and thus pose obvious problems for quantificational approaches, and they also do not seem to characterize kinds in terms of the principled or statistical connections investigated in previous research ( Prasada and Dillingham, 2006 ; Prasada and Dillingham, 2009). The second class — minority characteristic generics (e.g. “ducks lay eggs”) — also poses serious problems for quantificational accounts, and appears to involve principled connections even though fewer than half of its instances have the relevant property. The experiments revealed three principal discoveries: first, striking generics involve neither principled nor statistical connections. Instead, they involve a causal connection between a kind and a property. Second, minority characteristic generics exhibit the characteristics of principled connections, which suggests that principled connections license the expectation that most instances will have the property, but do not require it. Finally, the experiments also provided evidence that prevalence and the acceptability of generics may be dissociated and provided data that are problematic for normalcy approaches to generics, and for the idea that cue validity licenses low prevalence generics. As such, the studies provided evidence in favor of a conceptually based approach to the semantics of generics ( Leslie, 2007 ; Leslie, 2008; see also Carlson, 2009).

The present paper focuses on essentialism about natural kinds as a case study in order to illustrate this more general point. Saul Kripke and Hilary Putnam famously argued that natural kinds have essences, which are discovered by science, and which determine the extensions of our natural kind terms and concepts. This line of thought has been enormously influential in philosophy, and is often taken to have been established beyond doubt. The argument for the conclusion, however, makes critical use of intuitions, and I note that the intuitions are of the sort had by preschool children, and that they are traceable to a deep-seated cognitive outlook, which is often called “psychological essentialism.” Further, if we did not have such a cognitive outlook or implicit belief set—a belief set which is in fact in place by at least age 4—then we would not have the relevant philosophical intuitions. In light of this, I consider the question of whether natural kinds actually have scientifically discovered or discoverable essences, and whether these putative essences could determine the extensions of our terms and concepts as Kripke, Putnam, and many others have supposed. In fact, a number of philosophers of biology and chemistry have argued that biological and chemical kinds do not have such essences, yet these arguments—particularly in the case of chemistry—have not been assimilated by philosophers more generally. The reason for this poor assimilation is, I suggest, that the Kripke/Putnam view is just so intuitive. But this fact, I argue, is due to a deep-seated cognitive bias, rather than to any special insight into the nature of reality.