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Sunday, July 31, 2022

What is 'purity'? Conceptual murkiness in moral psychology

Gray, K., DiMaggio, N., Schein, C., 
& Kachanoff, F. (2021, February 3). 


Purity is an important topic in psychology. It has a long history in moral discourse, has helped catalyze paradigm shifts in moral psychology, and is thought to underlie political differences. But what exactly is “purity?” To answer this question, we review the history of purity and then systematically examine 158 psychology papers that define and operationalization (im)purity. In contrast to the many concepts defined by what they are, purity is often understood by what it isn’t—obvious dyadic harm. Because of this “contra”-harm understanding, definitions and operationalizations of purity are quite varied. Acts used to operationalize impurity include taking drugs, eating your sister’s scab, vandalizing a church, wearing unmatched clothes, buying music with sexually explicit lyrics, and having a messy house. This heterogeneity makes purity a “chimera”—an entity composed of various distinct elements. Our review reveals that the “contra-chimera” of purity has 9 different scientific understandings, and that most papers define purity differently from how they operationalize it. Although people clearly moralize diverse concerns—including those related to religion, sex, and food—such heterogeneity in conceptual definitions is problematic for theory development. Shifting definitions of purity provide “theoretical degrees of freedom” that make falsification extremely difficult. Doubts about the coherence and consistency of purity raise questions about key purity-related claims of modern moral psychology, including the nature of political differences and the cognitive foundations of moral judgment.


Purity is an ancient concept that has moved from historical religious rhetoric to modern moral psychology.  Many things have changed in this leap—Dr. Kellogg would never have imagined a scientific discipline catalyzed by loving incest—but purity still seems to be a heterogeneous concept with diverse understandings. This diversity makes purity an exciting topic to study, but our review suggests that purity lacks a common core, beyond involving acts that are less-than-obviously harmful.  Without a consistent and non-tautological understanding of purity, it is difficult to argue that purity is a unique and distinct construct, and it is impossible to argue for a mental mechanism dedicated to purity. It is clear, however, that purity is featured in moral rhetoric and can help shed light on cultural differences. Moving forward, we suggest that the field should unpack the richness of purity and individually explore its many understanding. When conducting this research, we should consider not only what purity isn’t, but what it really is.