Quest For Unification
  The GUT-based approach to physics has been attractive since it was first put forward close to thirty years ago; it has been enriched by new ideas, notably supersymmetry and strings; and there are real hints that it is on the right track, notably from measurements of the weak mixing angle and neutrino masses. In this article (based on my Heinrich Hertz lecture at SUSY 2002 at DESY, June, 2002), some of the arguments for grand unification will be reviewed. 
Edward Witten