Philosophical Capital and Sustainable Livelihoods: A Comprehensive Analysis of Small-Scale Polyculture Fisheries in Medan, Indonesia

Beyond the conventional five-capital sustainable livelihood framework, this research reveals the significance of philosophical capital—systems of values, local wisdom, and cultural practices—as a crucial dimension in the sustainability of small-scale polyculture fish farmers in Medan City, Indonesia. Through a survey of 89 fish farmers in Medan Labuhan and Medan Belawan Districts, this study develops and validates philosophical capital measurement instruments and analyzes their contribution to livelihood system sustainability through linear and non-linear approaches. Results show that the farmers' livelihood system falls into the "quite sustainable" category (SLCI = 0.571). Social capital emerges as the dominant component (index 0.6067), while philosophical capital (index 0.5290) contributes significantly by integrating traditional values into cultivation practices. Non-linear threshold effects analysis identified significant thresholds for natural capital (0.48), philosophical capital (0.51), and social capital (0.58), revealing how these capitals contribute to sustainability through different critical points. Comparative validation confirms that philosophical capital possesses strong psychometric properties (α = 0.87, AVE = 0.64) with the highest correlation to social capital (r = 0.58, p < 0.01). This research contributes to developing a more holistic sustainable livelihood analysis framework by identifying philosophical capital as a "meta-capital" that influences how other capitals are accessed and maintained. The implications include the importance of an integrative approach to policy development that accommodates local cultural values and dimensions as the foundation for resilience in small-scale polyculture fish farming livelihood systems.