Support is found for a fundamental role for the electromagnetic zero-point-field (ZPF) in the origin of inertia. Simply by requiring that that a universal noise field be selfconsistent in the presence of the lightest charge, it is shown that this field must be the ZPF, and that the mass of that charge must be close to 10⁻³⁰ kg. The ZPF functions as homeostatic regulator, with the electron mass decided by cosmological quantities. The calculation validates Dirac’s second Large Number hypothesis.