As early as the seventeenth century, German theologians and pedagogues had warned readers that excessive novel-reading could lead to seduction, superstition and fanaticism. Prescriptive literature urged literate women to confine their reading to devotional literature and household books. What had changed by 1850 was the scope and meaning of immoral writings', an elastic category that left room for many varieties of popular print. Legal language often involves the use of metaphor, and the police were able to draw parallels between the threat posed by immoral writings and other kinds of urban dangers. The metaphor of immoral books as harmful substances continued to inform regulation into the second half of the century. Psychiatry also led to efforts to link theories of criminality to 'immoral writings.' The fact that authority was partial, subject to debate and permeable tells something about the nature of power in post-revolutionary Berlin.