The Fermi Paradox asks: If there are billions of potentially habitable planets, why is the universe so silent? This paper proposes an answer that radically shifts the existing discourse: It is not technological barriers that prevent interstellar alliance capability, but ethical immaturity. The X∞ model describes a systemic governance principle that anchors responsibility as a mathematically operationalizable quantity. Accountability, capability-based impact capacity, feedback obligation, and protection of the vulnerable replace traditional power architectures. This logic applies not only to AI governance or societies but also to the question of which civilizations can stably navigate the transition to the singularity in the long term. The thesis of this paper: Ethical maturity, not intelligence, is the true filter criterion for interstellar alliance capability. X∞ is not a dogma but a structurally formulable connection logic—independent of biology, technology, or culture. This paper combines mathematical models, systems theory, ethical foundations, and current singularity research to provide a new answer to the universe’s quietest question.