This issue is dedicated to the memory of a delightful person, a wonderful mathematician, and a good friend. Marc Kac, born on August 16, 1914, died on October 25, 1984, was all these things to (almost) all who contributed to this volume and to many, many more who knew him and cherished him. Marc's company was ebullient on happy occasions and supportive on sad ones. You could always count on him to join wholeheartedly in a celebration or in a relief effort: he was indeed a man for all seasons.