Communities endure and cohere most effectively as harmonious, fluid structures because fixed points—rigid identities, absolute ideologies, unchanging hierarchies, or immutable norms—generate division. Human social life depends on ongoing coordination among individuals with overlapping but never identical interests, experiences, and capacities. When a community treats its boundaries, roles, and values as provisional and adjustable, it can absorb difference, renegotiate expectations, and maintain cooperation. When it elevates any element into a permanent, non-negotiable fixed point, that element becomes a fault line: membership is sorted into insiders and outsiders, status becomes zero-sum, and disagreement turns existential. Fluidity supports harmony for several interlocking social reasons. First, people change. Preferences, skills, alliances, and even self-conceptions shift across the life course and across contexts. A structure that insists on fixed categories—caste-like ranks, lifelo...