Current debates on the Enlightenment and its influence on present-day society call for an informed scholarly response. What exactly is the Enlightenment? What are its historical roots and how is it being used in current public debate? This project aims to contribute to such a response by introducing a specific tradition of urban lay philosophy—namely ‘vernacular rationalism’ in the Netherlands—as a new factor in our understanding of the rise and meaning of Enlightenment. As a secondary objective, the project aims to assess the relevance of lay philosophy generally for the understanding of early modern society and culture.This is achieved by (1) examining the philosophical and socio-cultural legacy of 16th-century vernacular rationalism and its function in the Dutch Golden Age, (2) using this to enhance our understanding of the Enlightenment as a historical phenomenon and as a historiographic notion, and (3) turning the case of vernacular rationalism into an informed illustration of the relevance of lay philosophy generally for early modern studies.Underpinning these research objectives is the strong conviction that it should be natural for intellectual historians to see philosophical ideas as responses to social, religious, political and other issues. The project will therefore reflect an interdisciplinary approach, seeking to integrate—under close monitoring of highly experienced multi/interdisciplinary supervisors—knowledge and methods from various fields of study. As such, it stands at the crossroads of philosophy, culture history and literary studies.By assessing, refining and correcting our knowledge of the foundations of present-day European society and culture, the project will enhance excellence and increase understanding on a subject directly relevant to the ERA and the EU at large.The mobility is genuine, as its aim is my training in a first-rate US environment and my re-integration into an outstanding multidisciplinary environment in Europe.