Arguments are given to support the notion that the thermally-forced component of large-scale motion is not simply that associated with pre-specified diabatic heat sources as expressed in the classical models of thermal forcing. the concept of thermal equilibration, as an idealized response in models with a Newtonian diabatic heating process, is introduced and is argued to be relevant to real and numerically simulated atmospheric circulation. Equilibration is possible when Newtonian forcing is compatible with a nonlinear free mode flow pattern. the general question of the possible importance of equilibration and nonlinear free mode structures in the atmosphere is raised.