This is the first of four volumes on the theory and application of nonequilibrium thermodynamics. Nonequilibrium theories are analyzed such as Onsagerian, rational, network-theoretic, information theoretic, Mullerian, finite time and extended. A perspective is given on the phenomenon of spatial and temporal structure formation in self-organizing systems and self-organizing criteria are presented, showing the importance of the concept of information. Recent results in network thermodynamics are reviewed, and in addition, geometric theories originating from Riemannian thermostatic curvature are extended to nonequilibrium situations. Statistical and stochastic aspects of the theory of nonequilibrium sytems are reviewed and their macroscopic consequences are shown. This is done in the context of recent generalizations of the so-called governing variational principle of dissipative processes and the associated extremum principles. An emphasis is put on new variational approaches of considerable generality, involving nondissipative and dissipative nonequilibrium continua which may contain matter or radiation. Radiation processes are treated on both statistical and phenomenological levels and the nonequilibrium thermodynamic theory of emitting and adsorbing media is developed. The book is intended for the use of chemical, process, industrial, thermodynamic/thermophysical and design engineers and should also be of use to researchers seeking detailed property data.