  We study scalar quark-anti-quark and two-quark-two-anti-quark correlation
functions in the instanton liquid model. We show that the instanton liquid
supports a light scalar-isoscalar (sigma) meson, and that this state is
strongly coupled to both $(\bar{q}q)$ and $(\bar{q}q)^2$. The scalar-isovector
$a_0$ meson, on the other hand, is heavy. We also show that these properties
are specific to QCD with three colors. In the large $N_c$ limit the
scalar-isoscalar meson is not light, and it is mainly coupled to $(\bar{q}q)$.
