The revival of mathematical physics that has taken place over the past decade and a half is the sort of development in modern science that I personally appreciate most. Mathematicians as well as physicists have had to travel great distances and overcome amazing obstacles in order to gather once again for fruitful collaboration. Eminent testimony of such a meeting is recorded in the report of the Vlll-th Course, held in the Villa Monastero in Varenna on Problemi Matematici della Teoria Quantistica delle Particelle Elementari e dei Campi.