Beginning in the 1960s, Horst W.J. Rittel (1930-1990) focused his research on the problems and problem-solving behavior of planners and designers. His discoveries have had a lasting impact on theories and methods in the fields of architecture and design, and form the basis of what is referred to today as "design thinking." At last, this new edition of his out-of-print collection of essays will make his texts accessible once again to German-speaking readers.