Fitouchi et al. illustrate the cognitive and evolutionary foundations of puritanical morality, while leave the emotional foundation unclear. We complement their theory by proposing moral emotions (e.g., guilt and shame) as characteristic emotions underlying puritanical morality. Our proposition is based on the findings that these moral emotions emerge after violations of puritanical norms and promote self-control and cooperation.

Commentators raise fundamental questions about the notion of purity (sect. R1), the architecture of moral cognition (sect. R2), the functional relationship between morality and cooperation (sect. R3), the role of folk-theories of self-control in moral judgment (sect. R4), and the cultural variation of morality (sect. R5). In our response, we address all these issues by clarifying our theory of puritanism, responding to counter-arguments, and incorporating welcome corrections and extensions.

Ownership is universal and ubiquitous in human societies, yet the psychology underpinning ownership intuitions is generally not described in a coherent and computationally tractable manner. Ownership intuitions are commonly assumed to derive from culturally transmitted social norms, or from a mentally represented implicit theory. While the social norms account is entirely ad hoc, the mental theory requires prior assumptions about possession and ownership that must be explained. Here I propose such an explanation, arguing that the intuitions result from the interaction of two cognitive systems. One of these handles competitive interactions for the possession of resources observed in many species including humans. The other handles mutually beneficial cooperation between agents, as observed in communal sharing, collective action and trade. Together, these systems attend to specific cues in the environment, and produce definite intuitions such as “this is hers,” “that is not mine.” This computational model provides an explanation for ownership intuitions, not just in straightforward cases of property, but also in disputed ownership (squatters, indigenous rights), historical changes (abolition of slavery), as well as apparently marginal cases, such as the questions, whether people own their seats on the bus, or their places in a queue, and how people understand “cultural appropriation” and slavery. In contrast to some previous theories, the model is empirically testable and free of ad hoc stipulations.

We applaud Boyer's attempt to ground the psychology of ownership partly in a cooperative logic. In this commentary, we propose to go further and ground the psychology of ownership solely in a cooperative logic. The predictions of bargaining theory, we argue, completely contradict the actual features of ownership intuitions. Ownership is only about the calculation of mutually beneficial, reciprocal contracts.

The psychology of ownership is rooted in self-ownership. The human brain has an evolved interoceptive sense of owning the body that supports self-ownership and the ownership of external things as extensions of the self-owning self. In this way, evolutionary neuroscience supports a Lockean liberal conception of equal natural rights rooted in natural self-ownership.

Boyer presents a compelling account of ownership as the outcome of interaction between two evolved cognitive systems. We integrate this model into current discussions of moral pluralism, suggesting that ownership meets the criteria to be a moral foundation. We caution against ignoring cultural variation in ownership norms and against explaining complex, contested moral phenomena using a monist approach.

We argue that ownership is a highly flexible concept, shaped by both innate and learned aspects, and heavily influenced by culture. Boyer's model focuses solely on universal personal ownership, neglecting other forms such as shared ownership, fractionalized property rights, and the ownership of the meanings and memories attached to possessions. A comprehensive understanding requires considering diverse human relationships with objects.

The developmental evidence for children's respect for ownership reveals that children will enforce the property rights of third parties before they themselves respect other's property. This pattern of development suggests the need for clarification or modification of the minimalist model. Here, I consider three explanations for the gap between knowledge and behavior for respect of ownership.

Every day, people make decisions about who owns what. What cognitive processes produce this? The target article emphasises the role of biologically evolved intuitions about competition and cooperation. We elaborate the role of cultural evolutionary processes for solving coordination problems. A model based fully on biological evolution misses important insights for explaining the arbitrariness and historical contingency in ownership beliefs.

Microbes perfect social interactions with intuitive logics and goal-directed reciprocity. These multilevel, cognition-resembling adaptations in Dictyostelid cellular molds enable individual-to-group viability through public/private bacterial farming and dynamic marketspaces. Like humans and animals, Dictyostelid livestock-ownership depends on environmental sensing, cooperation, and competition. Moreover, social-norm policing of cosmopolitan colonies coordinates farmer decisions, phenotypes, and ownership identities with bacteria herding, privatization, and consumption.

Human group size seemingly has no limit, with many individuals living alongside thousands – even millions – of others. Non-human primate groups, on the other hand, cannot be sustained past a certain, relatively small size. I propose that Pascal Boyer's model of ownership psychology may offer an explanation for such a significant divergence.

The target article claims that we should speak in code to understand property, because natural language is too ambiguous. Yet the best computer programmers tell us the opposite: Arbitrary code is too ambiguous, so we should use natural language for variables, functions, and classes. I discuss how meaningless code makes Boyer's theory too enigmatic to properly debate.

Boyer's cognitive model of ownership, based on cooperation and competition, underscores the importance of studying disagreements in ownership. We argue that exploring the factors that can lead to different perceptions and experiences of ownership will uniquely inform our understanding of legal, psychological, and perceived ownership beliefs.

We contrast Boyer's intuitive account of ownership with formal legal accounts based on institutions of ownership. Boyer's emphasis on social aspects of ownership intuitions may have a bearing on recent arguments that property institutions are justified by their capacity to promote human flourishing. Moreover, Boyer's account of property intuitions facilitates the study of acquisition and mental representation of formal ownership concepts.

Cooperation is fundamentally moderated by the form of relationship between the actors involved, as is normative resource distribution. We argue that possessions are likely treated differently across different types of cooperative relationships. Whereas Boyer's computational model might in principle account for this, the theory would benefit from a specification of how different cooperative contexts can shape the representation of ownership.

Boyer proposes that ownership intuitions depend on tracking cues predictive of agents’ motivations to compete for resources. However, the account may mis-predict people's intuitions about ownership, and it may also be too cognitively costly to be feasible. Even so, alternative accounts could benefit by taking inspiration from how the account handles thorny issues in the psychology of ownership.

We discuss and expand Boyer's idea of ownership coordination. Interpersonal similarity, we suggest, can moderate the attainment of coordination: Perceived similarity predicts coordination costs, whereas actual similarity dictates coordination success and the severity of illusory assumptions regarding a shared understanding of ownership. The example of similarity highlights the complexity of the social projection process uncritically assumed behind ownership coordination.

Ownership of resources can be established by evolved competitive and cooperative mechanisms as explained by the target article. However, there is one aspect of ownership that is not captured by computational models which is important to identity, namely the role of owned items as components of “the extended self” hypothesis.

Can Boyer's model of ownership psychology provide useful insights for comparative research? I apply his model to argue that we currently have evidence for possession psychology (based on competitive resource acquisition) in non-human primates, but not for ownership psychology.

Many languages grammatically distinguish between alienable and inalienable possessions. The latter are sometimes restricted to body parts, but they often include other kinds of personally significant entities too. These cross-linguistic patterns suggest that one's most precious owned objects tend to fall within a complex self system that includes not only the core (corporeal) self, but also the extended (noncorporeal) self.