This paper addresses the topic of seventeenth-century religious freedom of speech, focusing on the concepts conceived by Adam Boreel, an early member of the Dutch Collegiants. First, it gives historical information on Adam Boreel and the Collegiant movement. Second, it examines Boreel’s ideas concerning freedom of prophesying, highlighting how Boreel perceived this freedom and religious enthusiasm as unrelated. Third, it examines whether or not Boreel advocated an unlimited freedom of prophesying. In the conclusion, it suggests the significance of Boreel’s ideas for the history of the Collegiants and the broader history of ideas.