Reality is Singular, Mathematics are Plural: A Principle of Ontological Singularity with a Gap-Gated Instantiation Law for Quantum Foundations

Physical reality presents itself as a single, causally unified, decohering history, while the mathematical formalism of quantum mechanics is structurally plural: Hilbert space admits superposition, basis freedom, and infinitely many decompositions of any given state. This paper proposes the Principle of Ontological Singularity: formal plurality does not by itself entail ontological plurality. Against Everettian readings that treat decohered sectors of the universal wavefunction as emergent worlds, we argue that Schrödinger evolution supplies unitary dynamics, decoherence supplies approximately autonomous sector structure, and the Born rule supplies statistical weights, but none of these alone supplies worldhood. We formalize this distinction through an ordered pair , where is the plural mathematical map and is a realization selector designating the classically operative sector. We then address the central open question head-on: what determines ? We derive a Spectral-Born Instantiation Law in which the realized sector is selected stochastically from decoherence-stabilized pointer sectors according to Born weights, but only when a Liouvillian classical-instantiation gap exceeds a physical leakage threshold. The parameters of this law are grounded in decoherence timescales rather than left as free metaphysical constants. We introduce the principle of Temporarily Emergent Reality Framework (TERF): the territory is not a permanent feature of an ontological background but a configuration crystallized by conditions and sustained only while those conditions hold. Non-actualized branches are therefore not merely uninstantiated competitors; they are absent from the operative reality set entirely, with no bridge possible because there is nothing on the other end. We further argue that the Everettian ontological extension carries no experimental warrant: no experiment instantiates any additional world we can touch, and the equation’s evidential authority derives entirely from observations made within one causally accessible history. We discuss the law’s relationship to GRW/CSL collapse models, the structure of post-instantiation evolution including recursive refinement, T2 information mechanics at breakdown, and the cosmological scope of the framework—including the primordial kit state, environmentally contingent classical emergence, and the operative irrelevance of multiverse speculation to a framework whose jurisdiction is the territory we occupy. The proposal is presented as a map–territory discipline for quantum foundations: the map may multiply without limit, but the territory remains one—temporarily, contingently, and actually.