  This review of the quark-level linear \sigma model is based upon the
dynamical realization of the pseudoscalar and scalar mesons as a linear
representation of SU(2) x SU(2) chiral symmetry, with the symmetry weakly
broken by current quark masses. In its simplest SU(2) incarnation, with two
non-strange quark flavors and three colors, this nonperturbative theory, which
can be selfconsistently bootstrapped in loop order, is shown to accurately
reproduce a host of low-energy observables with only one parameter, namely the
pion decay constant f_\pi. Extending the scheme to SU(3) by including the
strange quark, equally good results are obtained for many strong,
electromagnetic, and weak processes just with two extra constants, viz. f_K and
$\langle\pi|H_{\mbox{\scriptsize weak}}|K\rangle$. Links are made with the
vector-meson-dominance model, the BCS theory of superconductivity, and
chiral-symmetry restoration at high temperature. Finally, these ideas are
cautiously generalized to the electroweak sector, including the W, Z, and Higgs
bosons, and also to CP violation.
