Between the years 1564–1606, the Heidelberg patrician, lawyer, collector, ‘lover of the painted arts’, and Calvinist church councillor Dr Marcus zum Lamm (1544–1606) compiled an unprecedented ‘treasury’ of printed and manuscript images and texts known as the Thesaurus Picturarum. The thirty-three surviving volumes which comprise Lamm’s understudied Thesaurus deal with an outstanding variety of subjects: ranging from ornithology, Reformation theology, prodigies and monstrosities, meteorology and astrology, through to costumes, art, ethnography, politics, and contemporary chronicles. As the first work to conduct a comprehensive review of Lamm’s collection, my thesis readdresses traditional assumptions about the relationship between images and subjectivity in a Calvinist milieu, one that scholars have far too long considered a culture of texts and iconoclasm. I question this historiographical tradition by demonstrating how the confessionalisation of humanist scholarship can be investigated through a Reformed courtier’s collection of images and, by analysing his choice of images and the themes he collated, interpret a Reformed world-view expressed visually. Lamm’s Thesaurus can be read as a visual ego-document and a subjective prism through which to view the development of the Calvinist Palatinate’s unique culture of religious consolidation and vibrant court fashioning c. 1555–1618; a context which the Thesaurus is—in many ways—a direct product of. However, at the same time, my thesis demonstrates how the feasibility and encyclopaedic scope of Lamm’s collection emerged, not only from local stimuli, artists, and personalities, but out of cosmopolitan, European and global, cultures of collecting and knowledge networks.