This paper explains the universality of Feynman diagrammatics from the perspective of Modal Triplet Theory. We show that propagators, vertices, and diagrammatic expansions arise inevitably from coherent modal fluctuations around stable fixed points with a dominant quadratic core and controlled interactions. Diagrammatics is shown to be a universal perturbative grammar of coherent systems, independent of quantization prescriptions. Projection to four-dimensional spacetime reproduces standard Feynman rules as a shadow of this upstream structure, while algebraic quantum field theory provides causal and renormalization control downstream.
Peter Nero (Wed,) studied this question.