  The Chapman-Enskog method of solution of the relativistic Boltzmann equation
is generalized in order to admit a time-derivative term associated to a
thermodynamic force in its first order solution. Both existence and uniqueness
of such a solution are proved based on the standard theory of integral
equations. The mathematical implications of the generalization here introduced
are thoroughly discussed regarding the nature of heat as chaotic energy
transfer in the context of relativity theory.
