Moral foundations theory (MFT; Graham et al., Reference Graham, Haidt, Koleva, Motyl, Iyer, Wojcik and Ditto2013; Haidt & Joseph, Reference Haidt and Joseph2004) was created to explain cross-cultural variation as well as cross-cultural similarities in moral judgments. MFT has four central claims: (a) There is a first draft of the moral mind (i.e., evolutionary processes created a universal initial configuration, not a tabula rasa); (b) the first draft of the moral mind gets edited during development within a culture; (c) intuitions come first, deliberative justifications come later; and (d) there are many psychological foundations of morality (see Graham et al., Reference Graham, Haidt, Motyl, Meindl, Iskiwitch, Mooijman, Gray and Graham2018). While the bulk of existing research has examined the initial list of five foundations (care, fairness, loyalty, authority, and purity), the founders of MFT have emphasized “moral pluralism” (i.e., that morality is more than one thing) rather than insisting on a fixed number of foundations. In fact, they have explicitly encouraged new foundations to be explored and added to MFT. Graham et al. (Reference Graham, Haidt, Koleva, Motyl, Iyer, Wojcik and Ditto2013, p. 58) paraphrased Isaiah Berlin in writing that they “do not know how many moral foundations there really are. There may be 74, or perhaps 122, or 27, or maybe only 5, but certainly more than one.” Graham et al. (Reference Graham, Nosek, Haidt, Iyer, Koleva and Ditto2011) posited that their original map of the moral domain (the five foundations) was “surely incomplete” (p. 382). So, what are these other foundations?

Since MFT was first described in 2004 (Haidt & Joseph, Reference Haidt and Joseph2004), we have tried to identify the candidate foundations for which the empirical evidence was strongest. We proposed five criteria for foundationhood (Graham et al., Reference Graham, Haidt, Koleva, Motyl, Iyer, Wojcik and Ditto2013): (a) Being common in third-party normative judgments; (b) automatic affective evaluations; (c) being culturally widespread though not necessarily universal; (d) evidence of innate preparedness; and (e) a robust pre-existing evolutionary model. As we proposed these criteria, we solicited criticism and feedback from our colleagues and even offered a prize to researchers who could demonstrate the existence of a new foundation or the need to re-arrange the old ones. Three potential candidates were winners of the challenge, and so at the time we thought “that Liberty/oppression, Efficiency/waste, and Ownership/theft [were] all good candidates for foundationhood” (Graham et al., Reference Graham, Haidt, Koleva, Motyl, Iyer, Wojcik and Ditto2013, p. 104). More recently, other researchers have also built upon MFT, developing different typologies of moral judgments with slightly different lists of foundations. Among these efforts is an interesting line of work by Curry, Mullins, and Whitehouse (Reference Curry, Mullins and Whitehouse2019), where they make the case for seven moral foundations: Family, group, reciprocity, bravery, respect, fairness, and property (which is the same as ownership). All in all, ownership has been on the radar of moral psychologists for a long time, and yet it remains one of the least studied constructs in this literature.

Boyer proposes a useful model of ownership as the outcome of interaction between two evolved cognitive systems, namely, competitive acquisition (i.e., competition for resources) and cooperation (e.g., sharing, trade). Boyer's minimalist model advances moral psychology and we largely agree with his claims. He effectively reviews ownership's foundationhood criteria: (a) Ownership is strongly present in third-party normative judgments (e.g., Gelman, Manczak, Was, & Noles, Reference Gelman, Manczak, Was and Noles2016); (b) consistent with the Social Intuitionist Model (Haidt, Reference Haidt2001), intuitions about ownership come quickly and without much deliberation; (c) ownership intuitions and norms are culturally widespread; (d) schemas of ownership appear in human infants (e.g., Noles, Keil, Bloom, & Gelman, Reference Noles, Keil, Bloom and Gelman2012; Tatone, Geraci, & Csibra, Reference Tatone, Geraci and Csibra2015); and (e) human intuitions about ownership (not just of land and objects, but of mates and children) have obvious parallels in other animals, and respect for property is an evolutionarily stable strategy. Boyer's model also offers a novel account of the evolution of ownership intuitions (which can interact with ecology and historical dynamics; see Bowles & Choi, Reference Bowles and Choi2013; Haynie et al., Reference Haynie, Kushnick, Kavanagh, Ember, Bowern, Low and Gavin2021).

Here, we suggest an expansion of Boyer's model to explicate substantial cross-cultural variation in the domains of ownership. Then we caution against attempting to account for highly complex social issues and moral phenomena such as slavery via a monist approach that ignores the plurality of moral concerns.

Boyer is not particularly attentive to culture in this target article. The actual “domain” of the ownership foundation can vary quite a bit across cultures. Resources such as water and land may be owned communally, individually, organized around kinship boundaries, or not at all. Intangibles such as intellectual property can be owned in modern societies, although the ownership foundation seems rather unresponsive to thefts of intangibles (e.g., downloading music illegally) compared with thefts of physical objects (e.g., music CDs in stores). In Western societies, differential endorsement of the ownership foundation is almost definitive of the left–right political axis. Marx's slogan “From each according to his ability, to each according to his need” is a beautiful ideal if you are an extreme communitarian and extreme egalitarian. But if your moral matrix rests heavily on the ownership and proportionality foundations (see Atari et al., Reference Atari, Haidt, Graham, Koleva, Stevens and Dehghani2022, for proportionality), then communism is an abomination that tramples on two foundations. Even the far milder versions of socialism and wealth redistribution that are supported by the left in most Western nations reveal that the left does not rely upon the ownership foundation as much as does the right. We have empirical evidence for this statement from several items we have tested at YourMorals.org in our exploration of a potential ownership foundation. For example, this item correlated r = 0.30 (N = 6459) with being on the left, politically: “If a person really needed to visit a friend in the hospital, and so he borrowed a stranger's bicycle for an hour, and the owner never found out, I would say this was OK.”

We also would like to give a cautionary note against analyzing morally reprehensible acts such as slavery from a monist perspective (as opposed to a pluralistic approach such as MFT's). As an alternative explanation to Boyer's theory about “contested ownership” and special cases such as slavery, we argue that intuitions in response to such transgressions can in fact be the outcome of tension between multiple moral foundations. For example, care, equality, proportionality, and liberty intuitions are strongly violated by slavery, as is evident in abolitionist literature and imagery.

In sum, Boyer's target article provides strong arguments that ownership is a moral foundation that should be incorporated within the broader MFT framework. More empirical evidence is needed to determine how this foundation develops, varies across cultures, and applies in contested domains. Intuitions about ownership seem to exist across human populations, although with enough variations in their scope and application to keep moral psychologists busy for a while.