This article examines the term “Radical Enlightenment” as a historiographical category through the lens of the philosophical work of Dorothea Christiane Erxleben (1715–1762), a keen advocate for women’s education and the first female medical doctor in Germany. The aim of the article is to develop a methodological framework that makes it possible to critically assess the radicalism of Erxleben’s philosophical position as it is presented in her highly systematic work Rigorous Investigation (1742). In the first part of the article, the (...) term “Radical Enlightenment” is briefly discussed in the German context. The second part is dedicated to articulating two methodological problems concerning the use of the term “radical” with regards to early feminist writings of the seventeenth and eighteenth centuries. The aim of this section is to develop a new approach to the classification of radical thinkers of this period. In the remaining three parts, this methodological approach is applied to the analysis of Erxleben’s views on equality and education, focusing on her call for women’s active participation in society. Finally, it is concluded that there is sufficient evidence to categorize vital parts of Erxleben’s philosophy as radical. (shrink)