This extended study of Thomistic concepts in the work of Franciscus Junius (1545-1602) is the first English monograph on Junius's theology in more than 40 years, and the first analysis of his use of Thomistic moral concepts. On a broad level, this project investigates the reception of Thomistic ideas in the early modern Reformed tradition. On a narrow level, this study contributes to an examination of Junius's moral theology itself.