The Fabric of Spacetime as Ontological Nexus: A Philosophical Treatise on the Substrate of Reality

This treatise advances a comprehensive philosophical account of the fabric of spacetime by drawing upon the Existential Nexus corpus (Boether, 2026). The central thesis is that the substrate of reality is neither a passive geometric container nor a merely relational structure between extended objects, but an ontological field constituted by the dynamic equilibrium between somethingness and nothingness. Through a synthesis of quantum field theory, general relativistic geometry, and the formal ontology of the Nexus framework, the fabric of spacetime is identified with the Existential Nexus itself: the equilibrium coordinate at which the complementary ontological states S⁺ (somethingness) and S⁻ (nothingness) converge to permit determinate, structured being. The physical manifestation of this ontological substrate is the quantum vacuum, whose substantive properties have been empirically confirmed through the Casimir effect and zero-point energy phenomena. The mechanics of the fabric are formalized through the ontological space Ω = ℝ₊ × ℝ₊, the existence function Ξ(σ, ν) = σ · ν · δ(t), and the conservation law σ(t) + ν(t) = B, the last following from Noetherian symmetry in the ontological Lagrangian. The treatise demonstrates that the fabric of spacetime is at once the geometric structure of general relativity, the energetic substrate of quantum field theory, and the ontological ground from which determinate existence emerges and into which it returns.