Goguen's contributions to fuzzy logic in retrospect

In the very early stage of the development of fuzzy logic, Joseph Goguen published profound work with lasting influence. Fifty years later, we provide an assessment of his contributions to fuzzy logic and thus pay tribute to Goguen, a former long-term member of the editorial board of this journal. We cover both Goguen's technical results, the research directions inspired by him, which have later been pursued, as well as his suggestions, which as yet remained explored to a lesser extent or practically unexplored.