Design as a draft of future visions is increasingly perceived as a field of competence that critically analyzes the process of transforming our ways of life in the 21st century, shapes it visionarily, and communicates it democratically. Horst W. J. Rittel (1930-1990) has made the problems and solution behaviors of planners, architects, and designers the subject of his research since the 1960s. His insights have laid the theoretical foundation for what is now known as Design Thinking. At the core is the realization that planning and design problems often evade the treatment methodologies offered by the sciences in a malignant manner. Rittel's achievement is recognizing both the transdisciplinary and political character of planning and design problems and developing theoretical concepts and a methodological framework for them.