This text reconstructs filtration at the highest level of abstraction compatible with the Possest–PQF framework. Against the trivial image of filtration as mechanical separation, it develops filtration as a regime of admissibility governing the transition from intensity to local operability. The argument proceeds simultaneously on conceptual, mathematical, biological, perceptual, technical, and political planes. Filtration is formalized as a nested threshold family, as a nonlinear dynamical evolution of admissibility, as a geometry of effective accessibility, as a persistence-bearing topological structure, and as a regime-producing chain capable of generating novelty only when the filtration itself changes. The result is a unified theory in which perception, memory, biological viability, platform visibility, public legibility, and conceptual stabilization appear not as separate domains but as distinct expressions of one and the same process: the production of admissible reality.