Monopole Substrate Theory (MST) is a conceptual framework that makes explicit the metaphysical commitments that physics has always required but never named. Rather than replacing existing mathematics, MST proposes that fields, particles, forces, and constants are not fundamental entities — they are mechanically necessary consequences of a single continuous substrate whose geometric properties generate every observable phenomenon as a parallax artifact of embedded observation. The framework introduces folding substrate vectors, parallax projections, and geometric friction to map event densities U(t), with direct descriptive mapping to general relativity (Einstein tensor), particle physics (Higgs potential), inflationary cosmology, and string theory manifolds. MST dissolves a number of outstanding problems in physics — including dark matter, dark energy, the Hubble tension, matter/antimatter asymmetry, wave function collapse, proton stability, and fine tuning — not by solving them individually but by removing the conditions that made them appear as separate problems in the first place. The paper includes a core phenomenological equation, a substrate taxonomy replacing the standard model particle zoo with a single stability spectrum, six testable predictions addressable with existing LIGO and Planck data, and a full physics mapping layer connecting MST geometry to standard physics descriptors. This work was developed outside academic specialization — reading across physics, philosophy, cosmology, and mathematics. The mathematical frameworks referenced are used as descriptive mappings. The conceptual framework is original to this work.