  This review is a simplified summary of the thermodynamic dislocation theory,
with special emphasis on the role of an effective temperature. Materials
scientists, for decades, have asserted that statistical thermodynamics is not
applicable to dislocations. By use of simple, first-principles analyses and
comparisons with experimental data, I argue that these scientists have been
wrong, and that this venerable field urgently needs to be revitalized because
of its wide-ranging fundamental and technological importance. In addition to
describing recent progress in understanding strain hardening, yielding, shear
banding, and the like, I argue that the thermodynamic dislocation theory can
lead to a much needed, first-principles understanding of brittle and ductile
fracture in crystalline solids.
