When tolerance enables its own destruction
This passage appears not in the main text but in a footnote (Chapter 7, Note 4) of Popper's magnum opus. Written in 1945 as World War II ended, Popper—an Austrian philosopher of Jewish descent—was grappling with how "a German public full of otherwise good people allowed Hitler to come to power."
A tolerant society allows all viewpoints, including intolerant ones, to be expressed freely.
Intolerant groups exploit this openness to spread their ideology and recruit followers.
Tolerant people tolerate intolerance, but intolerant people actively suppress tolerance.
Once intolerant groups gain enough power, they dismantle the tolerant system entirely.
Popper continues: "I do not imply that we should always suppress the utterance of intolerant philosophies; as long as we can counter them by rational argument and keep them in check by public opinion, suppression would certainly be most unwise."
The key trigger for action is when intolerant groups "are not prepared to meet us on the level of rational argument, but begin by denouncing all argument"—when they answer arguments with "fists or pistols."
Tolerance must be defended. A society that extends unlimited tolerance to the intolerant will ultimately be destroyed. Claim the right not to tolerate those who preach violence.
In "A Theory of Justice," Rawls argues a just society should tolerate even the intolerant—but reserves the right to self-preservation when intolerance threatens liberty and security.
Critics warn the paradox can be weaponized: Who decides what counts as "intolerant"? Vague definitions enable suppressing legitimate dissent under the guise of protecting tolerance.
Like the Prisoner's Dilemma: if tolerant people cooperate while intolerant people defect, defectors win. Stable cooperation requires a mechanism to punish defection.
The visualization above models a society as a grid of agents. Green (Tolerant) agents accept all views—even intolerance. Red (Intolerant) agents actively try to convert their neighbors and resist being converted. Yellow (Moderate) agents defend tolerance by resisting conversion AND converting intolerant neighbors back.
Try the "Unlimited Tolerance" scenario to watch Popper's prediction unfold: without defenders, intolerance spreads like a contagion. Then try "Defended Tolerance" to see how moderates who actively resist can maintain a stable, tolerant society.
The key insight: Pure tolerance is inherently unstable. Stability requires some members willing to actively defend tolerant norms—not through intolerance, but through principled resistance to those who would destroy the open society.