"Insanity in individuals is something rare - but in groups, parties, nations and epochs, it is the rule"

Nietzsche points to a paradox at the heart of human nature and society. As individuals, people usually act with a certain degree of logic, awareness, and restraint. True irrationality, going so far as to be labeled "insanity", is uncommon when someone is left to their own thoughts or private life. Decisions, emotions, and beliefs are shaped by personal experience and reflection, which often serves as a moderating force. However, the dynamic changes drastically when people come together in larger collectives, whether these are groups, political parties, nations, or even entire historical periods.

The collective mind takes on properties that do not merely reflect a sum of individual tendencies. Swept up by group identity, emotional contagion, ideology, or social pressure, people in collective settings often demonstrate behaviors and beliefs that defy individual logic. Mass hysteria, nationalism, moral panics, and ideological zeal reveal that a crowd can foster delusions, irrationality, and self-destructive impulses on a scale rarely seen in isolated individuals. The mechanisms at play, anonymity, lack of accountability, conformism, and the diffusion of responsibility, enable actions that would be unthinkable to most people when acting alone.

Nietzsche’s observation is especially striking when considered in historical context. Epochs are remembered as periods defined by their prevailing narratives, visions, and collective actions, which often include widespread fanaticism, violence, or social delusion. Mass movements, revolutions, wars, and systemic injustices are not anomalies in human history but recurring features, "the rule". Social and psychological factors conspire to dissolve individual reason, amplifying shared passions or prejudices until they become irresistible forces. Nietzsche does not merely diagnose a social ill but suggests that collective irrationality may be an inescapable feature of civilization, urging readers to reckon with the dangers inherent in the human tendency to subsume individuality within the group.