Bridging a gap in the literature, Professor Ericksen has drawn on his experience in research on solids to devise a series of lectures for graduates that introduce and illustrate uses of various important ideas with analysis which can be done using elementary mathematics. Simple strategies are discussed for thermoelastic bars and an ideal gas-solid mixture. Illustrative examples of thermodynamic stability theory include rudimentary analysis of cold-drawing in polymers, martensitic transformations in plates, instabilities in rubber balloons and sheets, peeling tapes, breaking bars, buckling of beams and instabilities produced by electromagnetic fields in liquid crystals. Non-equilibrium theory is illustrated by head conduction in rigid and deformable bars, including a fairly common way of using the Clausius-Duhem inequality to obtain thermodynamic restrictions on constitutive equations. Also covered is some elementary one-dimensional theory of shock waves and slower-moving phase boundaries. Finally, drawing on all these experiences, the last chapter treats general ideas in a more abstract way.