The schoolmistress and best-selling poet Anna Bijns was one of the few laypeople in the sixteenth-century Netherlands who was prepared publicly to fight for the Catholic cause. This article contends that Bijns's work, exceptional as it was, reflects a "moral" understanding of the problem of heresy that was not unique to her, but that exemplified the way in which many clerics responded to the threat of Protestantism. They equated heresy with sin, and argued that this required a penitential response from all in society. Yet by contending that each "order" in society was best left to fight its own sins, and that "each should tend his own garden" their arguments also created the impression that heresy was first and foremost a clerical problem. This may help explain the "passive" way in which Catholics in the Netherlands, as well as in many other parts of Northwestern Europe, responded to the Reformation.