viⅷ In Memoriam much more general sense,as his heart was always close to experimental activities. I knew Jun John for more than 25 years,and I had the greatest admiration not only for his immense also for the himself at Cornell during 1957-1958,he took time from his own pioneering research in K-nucleon dispersion relations to help me (via extensive corre- spondence)with my Ph.D.thesis on the same subject at Berkeley.Both Sandip Pakvasa and I were privileged to be associated with one of his last papers on weak couplings of heavy quarks,which displayed once more his infectious and intuitive style of doing physics.It is of course gratifying to us in retrospect that Jun John counted this paper among the score of his published works that he particularly enjoyed. The physics community suffered a great loss at Jun John Sakurai's death.The personal sense of loss is a severe one for me.Hence I am profoundly thankful for the opportunity to edit and complete his manuscript on Modern Quantum Mechanics for publication.In my faith no greater gift an opp ortunity to show my respect and love for San Fu Tuan