  We study the possibility that the light scalar mesons are (qbar qbar q q)
states rather than (qbar q). We perform a lattice QCD calculation of
pseudoscalar meson scattering amplitudes, ignoring quark loops and quark
annihilation, and find indications that for sufficiently heavy quarks there is
a stable four-quark bound state with J^{PC}=0^{++} and non-exotic flavor
quantum numbers.
