The problem of deriving irreversible thermodynamics from the re­ versible microscopic dynamics has been on the agenda of theoreti­ cal physics for a century and has produced more papers than can be digested by any single scientist. Why add to this too long list with yet another work? The goal is definitely not to give a gen­ eral review of previous work in this field. My ambition is rather to present an approach differing in some key aspects from the stan­ dard treatments, and to develop it as far as possible using rather simple mathematical tools (mainly inequalities of various kinds). However, in the course of this work I have used a large number of results and ideas from the existing literature, and the reference list contains contributions from many different lines of research. As a consequence the reader may find the arguments a bit difficult to follow without some previous exposure to this set of problems.