  Scalar mesons are a key expression of the strong coupling regime of QCD. How
those with $I_3=0$ couple to two photons supplies important information about
which is transiently ${\bar q}q$ or ${\bar {qq}} qq$ or multi-meson molecule or
largely glue, provided (i) we know the location of the corresponding poles in
the complex energy plane, and (ii) we have reliable predictions from strong
coupling QCD of the radiative widths for these compositions. Number (i) is
being supplied by careful analyses of high statistics data particularly that
coming from $B$, $D$, $J/\psi$ and $\phi$ decays. Number (ii) is still
required, before we can answer the question in the title.
