Many think of Edith Stein as a phenomenological philosopher who experienced a dramatic religious conversion, but contemporary adult educators may also look to her as a model for the application of social activism based in theory. This article explores Stein's continued relevance for adult educators who research and then try to apply key concepts related to transformative learning and social activism. The author first provides a context for her transformative learning experience, describes her social activism in 20th-century Germany, discusses how Stein integrated theory and practice, and then suggests key areas that could inform future research. Edith Stein left an unsurpassed but largely untapped legacy of adult education practice in three key areas for future research: how transformative learning can influence adult educators, the application of social activism in a tumultuous social-political environment, and the integration of theory and practice.