  Non-perturbative proof is presented of a unique version of Goldstone theorem,
that electromagnetism contributes to the masses of spinless particles of
quark-antiquark bound states in the form of a commutator of the quark electric
matrix and a coefficient factor which may be expressed simply in terms of a
three-body Bethe-Salpeter amplitude, in the case where the Lagrangian conserves
an approximate $SU(3)$ chiral symmetry. The coupled Bethe-Salpeter equation and
Dyson-Schwinger equation in the ladder-rainbow approximation are layed out with
every ingredient renormalized, which are applied to the problem of evaluating
the mass differences of some charged and neutral pseudoscalar and vector
mesons. The numerical results yield satisfactory agreement with experimental
observations for the mass spectrum and meson decay constants. Estimates of the
light quark masses are also given in the Bethe-Salpeter formalism.
