Effective field theory is among the most successful frameworks in modern physics, yet it is explicitly non-fundamental, non-invertible, and valid only within bounded regimes. In this work we show that these features are not contingent properties of particular quantum field theories, but structural consequences of describing physics through projection under finite admissibility. Wilsonian coarse-graining is identified as a non-injective projection from underlying dynamics to an effective description, the cutoff as an admissibility boundary, renormalization-group flow as induced effective evolution, and universality as equivalence under projection. The irreversibility of renormalization-group flow and the inevitability of effective field theory breakdown at strong coupling or high curvature follow directly from the projection–admissibility obstruction. No new dynamics or ultraviolet completion is proposed. Instead, effective field theory is shown to be the inevitable form taken by any stable, finite, predictive physical description. Modal Triplet Theory is discussed as an explicit realization in which this structure is controlled and calculable.
Peter Nero (Thu,) studied this question.