This paper highlights the role of Protestantism in seventeenth-century Japan, from 1600 to 1660. Far from being sidelined, it actually shaped the structure of conflicts between Reformed merchants (Dutch/English) and Catholic missionary merchants (mainly Spanish and Portuguese), as well as the relationship between the authorities and these two groups. This article looks in particular at written testimonies to demonstrate that faith mattered a great deal to the Reformed merchants, in their perception of themselves and in their representation to others, and that they sought to give definitions of their faith that revolved in particular around distinction from Catholics. To help us appreciate the richness and diversity of the forms these definitions take, this paper explores three ways in which they manifest themselves, starting with the less direct (image), then progressing to individuals (discourse), and finally to their bodies themselves (action).