Epistemic Limits and Ontological Completeness: Can the Physics of Our Universe Describe All Physical Reality?

This paper examines whether the laws and theories of physics developed to describe our observable universe can justifiably be regarded as a complete description of reality as a whole. It distinguishes epistemic limits—the constraints on what observers within a physical domain can know—from ontological claims about what exists beyond that domain. Drawing on the philosophy of cosmology, scientific underdetermination, and debates concerning multiverse hypotheses, the paper argues that the empirical success of physical theories within their tested domains does not, by itself, establish their universal ontological completeness. Mathematical consistency and conceptual possibility are likewise insufficient to demonstrate physical existence. The paper proposes a methodological framework for evaluating claims of completeness by examining the domain of a theory, the available evidence, the ontological commitments involved, and the justification for extending conclusions beyond the observed domain. It does not assert that realities beyond our universe necessarily exist; rather, it argues that the scope of our knowledge should not be confused with the scope of reality. The central conclusion is that the possibility of a more comprehensive reality remains an open philosophical question whose resolution requires more than the success of physics within our observable domain.