Schreiner argues that Europe in the sixteenth century was preoccupied with concerns similar to ours; both the desire for certainty -- especially religious certainty -- and warnings against certainty permeated the earlier era. Digging beneath overt theological and philosophical problems, she tackles the underlying fears of the period as she addresses questions of salvation, authority, the rise of skepticism, the outbreak of religious violence, the discernment of spirits, and the ambiguous relationship between appearance and reality.

In her examination of the history of theological polemics and debates (as well as other genres), Schreiner sheds light on the repeated evaluation of certainty and the recurring fear of deception. Among the texts she draws on are Montaigne's Essays, the mystical writings of Teresa of Avila, the works of Reformation fathers William of Occam, Luther, Thomas Muntzer, and Thomas More; and the dramas of Shakespeare. The result is not a book about theology, but rather about the way in which the concern with certitude determined the theology, polemics and literature of an age.