Sen's Theorem

Sen's Theorem is a fundamental result in social choice theory that states if certain fair conditions are met—specifically, that individual preferences are consistent, non-contradictory, and respect collective rationality—then there must be at least one collective decision (like a societal ranking) that aligns with these individual preferences without causing conflicts. Essentially, it demonstrates that when preferences are compatible and consistent, society can reach a rational, overarching agreement that reflects everyone's views, ensuring fairness and coherence in collective decision-making.