From a general theory of drying granular porous media, we have constructed a simplified theory that consists of a set of coupled, volume-averaged transport equations for the temperature and the saturation. The theory incorporates the liquid and vapor phase continuity equations, combines the liquid, solid and vapor phase thermal energy equations into a single temperature equation and makes use of Darcy's law for the liquid phase to account for moisture transport owing to capillary action. By purely qualitative reasoning, one can show that combined heat and mass transfer theories of drying cannot provide a complete theoretical explanation of drying phenomena and a detailed comparison between theory and experiment supports this point of view. Speculation concerning the logical course of subsequent theoretical studies is provided.