Dynamic Substrate Theory (DST): Foundation, Immanence, and the Rheological Paradox

Abstract Modern foundational physics often relies on exogenous finalities, fine-tuned cosmological constants, or arbitrary geometric impositions to explain cosmic structure. In this work, we formalize the foundational core of the Dynamic Substrate Theory (DST) by introducing the Postulate of Immanence and the Rheological Paradox. Rejecting external teleologies, we model the cosmic vacuum as a self-sustained continuous medium whose internal engine resides in the fundamental duality between structural elasticity (rigidity, memory, and form) and viscous relaxation (flow, change, and freedom). By employing a modified Maxwell-Oldroyd-B constitutive framework embedded within an intrinsic action functional, we demonstrate that vacuum stress-energy tensors and macroscopic evolution emerge entirely from internal continuum mechanics. Keywords: Dynamic Substrate Theory, Principle of Immanence, Rheological Paradox, Vacuum Mechanics, Viscoelastic Continuum.