  In this paper we examine the pair production through the Breit-Wheeler
process $\gamma~\gamma \to e^+ e^-$ in a thermal background. We compute the
thermal contribution to the Breit-Wheeler differential cross section within the
thermofield dynamics formalism. We evaluate in details the cross section for
this process, which possess a surprisingly simple expression valid for any
temperature $\beta$, from which we discuss some physically relevant aspects. We
also consider the high temperature regime of the cross section in order to have
a better understanding about its thermal behavior.
