Rationalizing right-handed neutrinos

A simple argument based on an SU(3) gauged horizontal symmetry is presented that connects the explanation for three generations of matter with the existence of a triplet of right-handed neutrinos. This rationale for right-handed neutrinos is analogous to, but completely independent of, grand unification or extra universal dimensions. A brief discussion of the supersymmetrized SU(3) model is also given, pointing out that certain problems in ordinary supersymmetric models such as fast proton decay via dimension-5 Planck-suppressed operators can be naturally solved.