These volumes contain a collection of essays by many of the closest co-workers of Raphael Hoegh-Krohn (1938-1988), one of the outstanding mathematical physicists of our age. The contributions vary in style, purpose, and content--some are surveys that summarize and clarify a subject area, others are new and adventurous expeditions into unknown territory. The topics cover most aspects of modern mathematical physics with special emphasis on methods from operator theory and stochastic analysis. Volume 1 contains papers on mathematical analysis (both linear and nonlinear), stochastics, and applications. Volume 2 discusses mathematical problems in quantum and statistical physics.