  There are two basic theoretical approaches to obtaining neutrino mass and
mixing. In the minimalist approach, one adds just enough new stuff to the
Minimal Standard Model to get $m_\nu \neq 0$ and $U_{\alpha i} \neq 1$. In the
holistic approach, one uses a general framework or principle to enlarge the
Minimal Standard Model such that, among other things, $m_\nu \neq 0$ and
$U_{\alpha i} \neq 1$. In both cases, there are important side effects besides
neutrino oscillations. I discuss a number of examples, including the
possibility of leptogenesis from R parity nonconservation in supersymmetry.
