Purity Testing
What it is
Setting increasingly narrow ideological criteria for group membership, expelling allies who fail arbitrary litmus tests.
How it works
Real-world examples
- •Political movements declaring long-standing supporters "problematic" for one disagreement on one issue.
- •Online communities demanding increasingly specific ideological commitments as prerequisites for participation.
- •Religious groups excommunicating members for questioning specific doctrines while maintaining overall faith.
Ethical guidelines
- ●Effective movements tolerate internal disagreement on specific issues while maintaining shared core values.
- ●Purity testing serves gatekeepers, not the movement's stated goals.
- ●The demand for perfect ideological alignment is itself a form of authoritarian control.
How to defend against it
- ►Movements that spend more energy policing members than opposing adversaries are in a purity spiral.
- ►Maintain your own principled positions rather than tracking shifting purity standards.
- ►Coalition-building requires tolerating disagreement — reject demands for ideological uniformity.
From the Defense Playbook
Restate the other side's position in its strongest form, to their satisfaction, before you answer it, so that you respond to the actual argument rather than to the caricature a persuader or your own side handed you.
When you argue across a political or cultural divide, make your honest case in terms of the values the listener actually holds, not your own, because arguments grounded in the other side's moral vocabulary are heard as arguments while those grounded in yours are heard as noise.
When you are handed exactly two choices, stop and generate at least one more before choosing, including doing nothing, doing both, doing part, doing it later, or pursuing the underlying goal in a different way.
Every playbook entry states how strong its evidence is and when not to use it. Browse the full playbook.
References
- Marques, J. M., Yzerbyt, V. Y., & Leyens, J.-P. (1988). The 'black sheep effect': Extremity of judgments towards ingroup members as a function of group identification. European Journal of Social Psychology, 18(1), 1–16Why yesterday's ally becomes today's enemy: strongly identified group members judged an unlikeable ingroup member more harshly than an equivalent outgroup member, because deviant insiders threaten the group's positive image more than outsiders do.
- Erikson, K. T. (1966). Wayward Puritans: A Study in the Sociology of Deviance. John Wiley & SonsThe entry's premise that groups maintain cohesion through boundary enforcement: Erikson's study of the Massachusetts Bay colony argues that communities define and police deviance in order to mark their moral boundaries, and manufacture new deviants when the boundaries need reaffirming.