  We analyze the $\gamma\gamma \to \pi^0\pi^0$ and $\gamma\gamma \to
\pi^+\pi^-$ reactions using the master formula approach to chiral symmetry
breaking. The pertinent vacuum correlators are estimated at tree level, and the
results are compared with one- and two-loop chiral perturbation theory. The
Compton scattering amplitude and the pion polarizabilities are also discussed.
