Whitehouse argues that extreme self-sacrifice for the benefit of the group emerges through two pathways. First, people may go through transformative experiences with other group members (e.g., life-changing ordeals or highly arousing rituals), creating a visceral sense of oneness between the self and the group. Second, people may perceive that they share essential biological properties with the group, either because they literally have shared phenotypic characteristics (local fusion) or because group norms and practices emphasize obligations of kinship and common ancestry (extended fusion).

As an account of why people might die for their own group, the target article provides an impressive and plausible theoretical perspective. However, even the broader conceptualization of extended fusion – fusion among “much larger group categories, such as country, ethnic group or world religion” (sect. 6, para. 1) – is limited to explaining extreme self-sacrifice within the bounds of shared biological or ideological markers. Therefore, as a “general theory of extreme self-sacrifice,” the article misses one relevant dimension: people's willingness to risk their lives in support of people and entities that are not bound by biological markers or a sense of ancestral kinship (allyship).

Allyship refers to individuals becoming committed participants in collective action to improve the treatment of disadvantaged out-groups (Droogendyk et al. Reference Droogendyk, Wright, Lubensky and Louis2016). Examples of allyship that potentially involve extreme self-sacrifice include Anglo-Americans risking their lives in support of African Americans (e.g., the civil rights movement, the Charlottesville protests) and radical environmentalism in support of wildlife and non-human animals (e.g., Greenpeace, Sea Shepard). We propose an extension to the target article that accounts for the occurrence of extreme self-sacrifice in circumstances where shared essence is less conceivable or apparent. Just as fusion can motivate extreme self-sacrifice for the benefit of local and extended groups, we propose that an expanded sense of moral obligation can motivate extreme sacrifice for the benefit of those beyond it.

History shows that we continually expand our moral sensibilities to defend the moral standing of entities beyond biologically predictable limits (Pinker Reference Pinker2011; Singer Reference Singer1981). Research on the psychological construct of moral expansiveness has uncovered that some individuals perceive “distant” others (e.g., members of national and religious out-groups and non-human animals) to possess high levels of moral worth. As a result, they feel a moral obligation to defend these entities, even at personal cost (Crimston et al. Reference Crimston, Bain, Hornsey and Bastian2016; Reference Crimston, Hornsey, Bain and Bastian2018). Singer (Reference Singer1981) proposed that this extension of the moral circle is accompanied by the perception that – from the perspective of the universe – one's life holds no unique moral value.

In line with this, we found that the higher individuals were in moral expansiveness, the more they reported a willingness to make costly sacrifices to benefit people and entities that lie outside traditional notions of in-group membership or common ancestry (Crimston et al. Reference Crimston, Bain, Hornsey and Bastian2016). For example, those high in moral expansiveness were more willing to donate a kidney to “distant” others, including refugees and murderers. In other studies, we introduced a hypothetical evil dictator game: Participants were asked to imagine that a dictator had passed laws that placed a range of specific groups and entities at risk of being wiped out. However, if somebody volunteered to sacrifice him- or herself, the groups would be saved. Participants were asked how many of these groups and entities would need to be killed before they would lay down their own lives to save them. Those high in moral expansiveness indicated a willingness to sacrifice themselves earlier, not just to save people from their hometown, but also Africans, chimpanzees, and redwood trees. Crucially, these relationships held after controlling for numerous alternative constructs, including extended identification with humanity, connectedness with nature, endorsement of universalism values, and empathy. This highlights the unique role of moral expansiveness in predicting extreme sacrificial attitudes.

Additional work from the field of moral psychology can shed light on why an individual might engage in – or, at the very least, report a strong urge to engage in – these acts of extreme self-sacrifice. People typically consider the rights and well-being of entities at the center of their moral circles to take precedence over other considerations. It is likely that these perceived obligations are held with such deep moral conviction that they become “moral mandates” (Skitka et al. Reference Skitka, Bauman and Sargis2005). Indeed, moral convictions have been identified as a potential antecedent of allyship, as they provide powerful motivation for a call to action (van Zomeren et al. Reference van Zomeren, Postmes, Spears and Bettache2011). Such deeply embraced moral convictions go beyond mere attitudes or beliefs; rather, they are held with extreme significance and certainty, and produce visceral emotional responses with high action potential (Mullen & Skitka Reference Mullen and Skitka2006). Therefore, moral conviction may serve as a catalyst for these extreme self-sacrificial acts beyond the bounds of the group.

In sum, Whitehouse's work offers a compelling theoretical account of why individuals may be willing to lay down their lives for the sake of their groups and the crucial role of identity fusion in this process. We offer an extension, highlighting the powerful and unique role an expansive sense of moral obligation can play in the occurrence of extreme self-sacrifice beyond the boundaries of shared markers.