Constitutive equations have been formulated for the mechanical behavior of isotropic, elastic materials that dewet. This has been accomplished in part through an application of the stability postulate of Drucker, the implications of which underlie most of the fundamental results of the classical inviscid theory of plasticity. From a phenomenological viewpoint, the two theories differ in the nature of unloading, their dilation behavior, and the form taken by the de‐wetting criterion, which is analogous in the present theory to the yield criterion in plasticity.