QGD / MPDT and MOND: Achievements, Structural Challenges, and a Minimal Axiomatic Alternative

Modified Newtonian Dynamics (MOND), introduced by Milgrom in 1983, reproduces flat rotation curves, the baryonic Tully–Fisher relation, and the radial acceleration relation across hundreds of galaxy types using a single parameter a₀ — an economy that neither Newtonian gravity nor ΛCDM can match. These achievements are genuine and deserve acknowledgment before critique. This paper argues that MOND's success is purchased at a foundational cost: a₀ is posited without derivation, the framework inherits Newton's dependence on time as a primitive, and no consistent relativistic extension has survived observation (TeVeS was ruled out by GW170817). Under the MPDT metatheoretic standard, MOND is a sophisticated phenomenological parametrization, not a fundamental theory. Quantum-Geometry Dynamics (QGD) derives gravity from two axioms — discrete space (preons(−)) and kinetic matter (preons(+)) — producing a distance-independent attractive force (p-gravity) and a distance-amplified repulsive force (n-gravity), without time as a primitive. The structural source of MOND's empirical regularities is identified as the free preonic background: unconsolidated preons(+) that contribute to p-gravity at galactic radii and whose density transition marks the scale a₀. QGD does not derive the inverse-square law; it provides a different, axiomatically grounded account of the same gravitational dynamics. The quantitative derivation of a₀ from QGD's grounding constants is an open programme (P14); the structural identification is derivable in principle from the axioms. The broader observational record — Bullet Cluster, dark-matter-deficient galaxies, dark galaxies, JWST early galaxy excess, large-scale structure — confirms QGD's account while requiring MOND to reintroduce the dark matter component it was designed to eliminate.