A recent development in moral psychology with important theoretical consequences is the division of morality into distinct domains (Rozin, Lowery, Imada, & Haidt, Reference Rozin, Lowery, Imada and Haidt1999). One such hypothesized moral domain has become the focus of intense research: purity. Purity was theorized to be distinct from other moral domains, such as autonomy for example. Autonomy violations occur when a perpetrator intentionally harms another person and thereby elicits anger in a witness, whereas purity violations occur when the perpetrator, intentionally or not, defiles his or her own body or soul and thereby elicits disgust in a witness (Rozin et al., Reference Rozin, Lowery, Imada and Haidt1999). However, more recent research questions whether purity is distinct from autonomy (Gray, DiMaggio, Schein, & Kachanoff, Reference Gray, DiMaggio, Schein and Kachanoff2022; Kollareth, Brownell, Durán, & Russell, Reference Kollareth, Brownell, Durán and Russell2023).

Consistent with the recent questioning of purity as a distinct moral domain, Fitouchi et al. raise the question whether a subset of violations in the purity domain, what can be called puritanical morality (condemnation of lust, gluttony, drinking, drugs, gambling, etc.) is an exception to the cooperative function of moral cognition. They propose moral disciplining theory (MDT) and argue that at least some acts featured in puritanical morality are cooperation-based moral concerns. If so, such acts, allegedly understood as violations in the domain of purity, lack distinct psychological foundations and evolutionary concerns said to characterize that domain.

That violations of purity are characterized by a unique emotion, disgust, is also questionable. Fitouchi et al. argue that puritanical moral acts such as lust, gluttony, intemperance, lack of self-discipline, and impiety are unrelated to disgust. Furthermore, much of the research offered in support of the claim that purity violations are disgusting confounds the violation with a pathogen. Examples include: thinking of scriptures while expelling excrement (Haidt, Reference Haidt, Keyes and Haidt2003) or cleaning a bathroom with the national flag (Haidt, Reference Haidt2012; Haidt, Koller, & Dias, Reference Haidt, Koller and Dias1993). When studies de-confound purity violations from pathogens, those alleged purity violations are not perceived as disgusting (Kollareth & Russell, Reference Kollareth and Russell2019; Kollareth et al., Reference Kollareth, Brownell, Durán and Russell2023; Royzman, Atanasov, Landy, Parks, & Gepty, Reference Royzman, Atanasov, Landy, Parks and Gepty2014).

Fitouchi et al. also note that the word disgust is polysemous. Thus, there is a problem using the word disgust to measure the emotional reaction of disgust. The word disgust is synonymous with “grossed-out” when the target includes a pathogen. However, in other contexts, a witness may use the word disgust to indicate anger or even dislike. In studies that used the word gross or phrase grossed-out in the response format, purity violations free of pathogens were more angering than gross (Kollareth & Russell, Reference Kollareth and Russell2019; Kollareth et al., Reference Kollareth, Brownell, Durán and Russell2023; Royzman et al., Reference Royzman, Atanasov, Landy, Parks and Gepty2014).

A similar confound occurs with the use of an emotional facial expression as a measure of disgust. The standard disgust face (nose-scrunch, raised upper lip) is associated with both disgust and anger (Pochedly, Widen, & Russell, Reference Pochedly, Widen and Russell2012; Rozin, Lowery, & Ebert, Reference Rozin, Lowery and Ebert1994; Widen & Russell, Reference Widen and Russell2010). However, the face of someone about to vomit (open mouth, lowered bottom lip, cheeks raised), which we call the “sick face,” was more reliably associated with pathogen disgust (Widen, Pochedly, Pieloch, & Russell, Reference Widen, Pochedly, Pieloch and Russell2013). Studies have shown that the standard disgust face is commonly interpreted as angry rather than disgusted (Pochedly et al., Reference Pochedly, Widen and Russell2012; Rozin et al., Reference Rozin, Lowery and Ebert1994; Widen & Russell, Reference Widen and Russell2010). Ekman (Reference Ekman and Cole1972) found what he called a “confusion” of anger and disgust when Papua New Guineans selected faces for basic emotions. Opposing the view that purity violations (free from pathogens) elicit genuine disgust, Ritter, Preston, Salomon, and Relihan-Johnson (Reference Ritter, Preston, Salomon and Relihan-Johnson2016) found that religious thought violations were not associated with the standard “disgust face” that was elicited by physically disgusting stimuli.

Yet another question raised by Fitouchi et al. in relation to disgust is whether behaviors that degrade the elevated nature of the human soul or remind humans of their animal nature are disgusting. Empirical studies have examined this specific hypothesis and conclude: Animal reminders per se are not disgusting (Kollareth & Russell, Reference Kollareth and Russell2017). Some disgusting things may remind us of our animal nature, but they are not disgusting because they do so (Kollareth & Russell, Reference Kollareth and Russell2018).

Consistent with the idea of purity violations degrading one's spiritual self, Rottman, Kelemen, and Young (Reference Rottman, Kelemen and Young2014) offered “taint to soul” as a marker of a purity violation. However, studies show that purity violations are not the only type of moral violation that a witness believes taints or degrades the soul (Kollareth et al., Reference Kollareth, Brownell, Durán and Russell2023). Witnesses find that murder, a hypothesized autonomy violation, taints the soul of the perpetrator more than does suicide, a hypothesized purity violation (Allam, Kollareth, & Russell, Reference Allam, Kollareth and Russell2022).

Yet another hypothesized marker of a purity violation is related to the role of intention. According to Young and Tsoi (Reference Young and Tsoi2013), “mental states, in fact, matter less, specifically, in cases of ‘purity’ violations” (p. 586). Initial research provided some support for this hypothesis (Barrett et al., Reference Barrett, Bolyanatz, Crittenden, Fessler, Fitzpatrick, Gurven and Laurence2016; Chakroff et al., Reference Chakroff, Dungan, Koster-Hale, Brown, Saxe and Young2016). However, more recent studies emphasize the role of the perpetrator's intention in the judged morality of various violations including those of purity. Context rather than domain governs the role of the perpetrator's intention (McHugh, McGann, Igou, & Kinsella, Reference McHugh, McGann, Igou and Kinsella2022). When context is taken into account, intention plays a significant role in the judged immorality of purity violations just as it does for autonomy violations (Kupfer, Inbar, & Tybur, Reference Kupfer, Inbar and Tybur2020; Parkinson & Byrne, Reference Parkinson and Byrne2018). In the purity domain, the perpetrator's intention is significant and substantial: It is used to judge whether an impure act is moral or immoral (Kollareth & Russell, Reference Kollareth and Russell2022).

In short, although every moral violation is distinct, empirical evidence does not support the claim of a distinct moral domain of purity. Indeed, violations characterized as purity overlap in many ways with other hypothesized moral domains – a claim consistent with Fitouchi et al.'s interesting and important hypothesis that puritanical morality is part of cooperation-based morality.