How Is Bottom-Line Unity Possible? Common Bottom Lines and Their Governance Mechanisms in a Plural World

The cross-border diffusion of global risks has not automatically eliminated value divergence and fragmentation of action, which places an evident limit on community-building practices premised on the homogenization of higher-order values. This paper uses "bottom-line unity" to capture the alternative approach: actors need not eliminate value differences, yet they must form minimal common judgments about the non-breakable boundaries that concern human survival, security, dignity, development, and the future, and translate those judgments into differentiated responsibilities and institutional constraints. The paper proposes four recognition criteria, categorizes bottom lines into eight domains within four tiers (existence, risk, justice, and order); analyzes five mechanisms of bottom-line failure (insufficient cognition, absent responsibility, politicization, institutional gaps, and temporal mismatch); identifies three types of blocking forces (geopolitical power capital, algorithmic cognitive cocoons, and short-term electoral interests) and the corresponding checks; and develops a five-step governance mechanism of bottom-line recognition, minimal consensus, responsibility allocation, institutional embedding, and violation correction, which is then applied to nuclear risk, climate governance, and lethal autonomous weapons systems. The study shows that shared risks can generate minimal order only when they are transformed into stable public knowledge, supported by plural reasons, distributed as legitimate and differentiated responsibilities, and embedded in institutions capable of monitoring and correction; bottom-line unity does not replace the higher-order ideals of the community but provides the minimal guarantee against their collapse.