This treatise attempts to portray the ideas and general principles of the theory of materials within the framework of phenomenological continuum mechanics. It is a mathematical introduction to classical continuum mechanics and deals with concepts such as elasticity, plasticity, viscoelasticity and viscoplasticity in nonlinear materials. The aim of a general theory of material behaviour is to provide a classified range of possibilities from which a user can select the constitutive model that applies best. The book will be invaluable to graduate students of materials science in engineering and in physics.