Peter the Hermit: Straddling the Boundaries of Lordship, Millennialism, and Heresy demonstrates how eleventh and early twelfth century wandering preachers established millennial spiritual lordship over their popular movements. Peter the Hermit's Popular Crusade exemplifies this.

Millennial spiritual lordship accessed millennial undercurrents of medieval society at the time and often the reform movements of the church. Such lordship stood just outside the traditional secular and spiritual lordships of the period. Indeed, a millennial spiritual lord could find himself being accused of heresy, since the energies that drove reform also drove supposed heretical movements. These kinds of lordships also followed patterns typical of millennial movements.

Although Peter the Hermit was not accused of heresy, he was not officially supposed to go on the First Crusade. Had his energies been directed inward, toward the church, he would have been charged with heresy, just like some of his contemporaries and later preachers.

Other itinerant preachers examined include: Robert of Arbrissel, Tanchelm of Utrecht, and Henry of Le Mans.