Entanglement Compression Theory (ECT) derives probability, deterministic quantum dynamics, and spacetime curvature from a single structural requirement: existence must persist as motion, and the simplest persistent motion is oscillation. From this requirement, probability, geometry, and general relativity arise as deterministic consequences rather than independent postulates. This paper introduces the Oscillation Principle, the assertion that static states are physically untenable and that oscillation is the only realizable form of existence. Energy, motion, and wave behavior are not separate constructs but a single entity, expressed concisely as waves = motion = energy. From this premise, entanglement, compression, and probabilistic structure follow as necessary outcomes. Planck units, historically treated as dimensional cutoffs, are reinterpreted as descriptors of the minimal oscillatory event: ℓₚ as spatial span, tₚ as temporal recurrence, and Eₚ as causal amplitude. These quantities define the indivisible unit of motion from which dimensionality arises. Dimensional extension appears as the projection of oscillatory amplitude, with curvature emerging when compression reaches its entropy boundary. Within ECT, the local speed of light arises from compression through c(x)² = T(x)/C(x), where T(x) denotes tension and C(x) compression. Probability emerges through deterministic energy partition, while curvature arises from compression gradients. The Oscillation Principle unifies these relations and provides a geometric interpretation of ℓₚ, tₚ, and Eₚ as properties of the primordial oscillatory event. Traditionally, energy, motion, and wave behavior have been treated as distinct categories. This framework resolves them as projections of a single oscillatory process, providing a unified foundation for quantum and relativistic phenomena. This paper serves as the conceptual foundation of Entanglement Compression Theory. The Oscillation Principle states directly that waves, motion, and energy are one, under the logical requirement that existence cannot be static. Readers seeking formal derivations, operator structure, and falsifiability protocols should consult Theory of Derived Probability and Entanglement Compression (DOI: 10.5281/zenodo.15786696) and its Mathematical Foundations companion. For a visual demonstration of deterministic structure emergence under the Primordial Wave Equation (PWE) and its prediction of dark-matter-like halos, see the Compression Theory Institute site: https://compressiontheoryinstitute.org. Version 4 (February 9, 2026).Replaced incorrect DOI in header Version 3 (January 2026).This version introduces a constraint-based structural justification of the Oscillation Principle, clarifying why persistent motion necessarily takes oscillatory form. No physical claims, formal results, or conclusions are altered. Version 2 (January 2026).This version reflects minor editorial alignment performed to clarify axiomatic classification, canonical ordering within Entanglement Compression Theory, and consistency of language with later foundational papers. No substantive claims, derivations, or conclusions have been altered from the original 2025 release.

ECT Internal Topics and Constructs: Oscillation Principle, Entanglement Compression Theory (ECT), Derived Probability, Primordial oscillation, Planck units, Planck Time, Planck Energy, Planck Length, Quantum gravity, Wave–energy equivalence, Mass–energy equivalence, Curvature and compression, Spacetime emergence, Cosmology, Foundations of physics, Quantum foundations, Probability derivation, Entanglement, Compression scalars, Causation, Dimensionality, Wave mechanics, Unified physics, Quantum Theory, Quantum physics