Edith Stein's life and thought intersect with many important movements of life and thought in the twentieth century. Through her life and even-tual martyrdom, she gave witness to the primacy of truth and faith in the face of political totalitarianism, and in her philosophical works, she con-tributed to a synthesis of phenomenological thought with the thought of Aquinas, while also progressively advancing a compelling form of philosophical personalism. As a result, Stein represents one of the most important Catholic thinkers of the twentieth century and is a figure of growing fascination and devotion among believers and nonbelievers alike. The Personalism of Edith Stein is an investigation of Stein's mature phil-osophical anthropology, exploring her engagement with the thought of Aquinas and Thomism while maintaining the phenomenological mode of investigation. Through a careful examination of Stein's later works un-der the themes of human nature, the human individual, and the human being's relation to God, McNamara shows that Stein's mature personal-ism is considerably expanded and substantiated by her assimilation of key anthropological and metaphysical teachings of Aquinas and Thom-ism, and, conversely, that Stein significantly develops and deepens these same teachings through a phenomenological reconsideration of each from a personalist perspective. As a whole, the study reveals the profound accord between Stein's mature thought and the received teachings of Aquinas, while yet care-fully attending to the remaining differences between them. Ultimately, the author proposes that Stein imbues the teachings of Aquinas with a fundamental personalization such that her mature anthropology can be understood as a Thomistically informed personalism which represents a significant, original contribution to the anthropological dimension of the philosophia perennis.