Paul Adrien Maurice Dirac, one of the greatest physicists of the twentieth century, died in 1984. Dirac's college, St John's of Cambridge, generously endowed annual lectures to be held at Cambridge University in his memory. This volume contains a much expanded version of the 1994 Dirac Lecture by Nobel Laureate Pierre Gilles de Gennes. The book presents an impressionistic tour of the physics of soft interfaces. Full of insight and interesting asides, it not only provides an accessible introduction to this topic, but also lays down many markers and signposts for interesting new research possibilities. The text begins with a brief discussion of wetting and dewetting and then goes on to consider the dynamics of different types of interface before considering adhesion and polymer/polymer welding.