Population Decline as Ontological Consequence: Falsifiability Immunity, Generativity Contraction, and the Structural Convergence of Advanced Societies

Population decline is no longer a regional anomaly but a structural global convergence.Institutional explanations—economic, cultural, or political—have failed to account for its persistence.This paper argues that fertility collapse reflects a deeper ontological shift toward optimized existence.As life becomes a project of stabilization and calculation, generativity contracts.Demographic decline thus signals not social malfunction but civilizational phase transition. HIGHLIGHTS 1. Fertility decline across advanced societies cannot be explained by single institutional variables such as capitalism, feminism, or marital change. 2. Systematic refutation of surface causes produces a “falsifiability-immunity” mechanism that obscures deeper structural dynamics. 3. Modern institutions function as transmission channels of an optimization-centered ontology (S-ontology) rather than isolated causal drivers. 4. As time, attention, and life planning become fully optimized, generativity (Φ) is redefined as opportunity cost, leading to contraction of the generative basin. 5. Population decline should be interpreted as a civilizational phase transition in which divergent institutions converge toward a shared ontological structure. ABSTRACT Population decline has emerged as a defining structural feature of advanced societies. Despite extensive demographic research, no single institutional factor—economic system, gender regime, or family structure—adequately explains the global convergence toward sub-replacement fertility. This paper proposes that the persistence of low fertility reflects a deeper transformation in the ontological organization of life rather than isolated policy or cultural failures. The analysis introduces a layered causal framework distinguishing surface institutional variables, transmission mechanisms, and deep ontological structure. While comparative demographic research has successfully refuted monocausal explanations of fertility decline, this very process has generated a “falsifiability-immunity” effect in which the dismissal of individual causes obscures the shared structural conditions underlying demographic convergence. The paper identifies S-ontology—an optimization-centered mode of existence in which life is organized around stabilization, measurement, and opportunity maximization—as the underlying structural condition. Within this framework, reproduction is increasingly evaluated as a long-term allocation decision within an already saturated optimization field. Generativity (Φ), once foundational, becomes conditional and often deferred. A comparative structural overlay of Japan, France, and South Korea demonstrates how divergent institutional arrangements produce convergent demographic outcomes. Differences in welfare regimes, gender relations, and marital patterns shape transmission pathways but do not alter the underlying orientation toward optimized existence. Fertility decline thus reflects contraction of the generative basin across distinct social contexts. Population decline is therefore interpreted as a civilizational phase transition rather than a demographic anomaly. As optimization becomes the dominant organizing principle of life, generativity contracts structurally. Understanding contemporary demographic change requires moving beyond institutional explanations toward an ontological analysis of modern social organization. Author’s Related Works Ohumi, K. (2025). Manifesto of the Life OS: The "It from Wave" Philosophy. Zenodo. https://doi.org/10.5281/zenodo.18106437 Ohumi, K. (2025). A Sampling-Theoretic Reinterpretation of Quantum Uncertainty and Wave Function Collapse. Zenodo. https://doi.org/10.5281/zenodo.18004579 Ohumi, K. (2025). 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