Questions and answers about a thermodynamic theory of the third type

Nonequilibrium thermodynamics has several faces: the most popular theory, referred to as thermodynamics of the first type, is the classical theory of irreversible processes developed essentially by Eckart, Meixner, Onsager and Prigogine. Another more general but more formal approach–the so-called thermodynamic theory of the second type–was proposed by Coleman, Noll and Truesdell and was named by its founders ‘rational thermodynamics’. By thermodynamics of the third type is understood the so-called extended irreversible thermodynamics; the latter has fuelled much interest during the last decade. In the present work, the main ideas underlying this formalism are reviewed. Moreover, questions about the foundations, contents and aims of this new theory are raised. Tentative answers are provided.