Joaquim Marques de Araújo ardently defended the Portuguese Inquisition for fifty years, only to find himself sidelined and forgotten. In Defence of the Faith offers an insightful examination of one man's career as a comissário of the Portuguese Inquisition in Pernambuco, Brazil, from 1770 to 1820. James Wadsworth argues that as legal extensions of the inquisitors in Lisbon, the comissários played a role far superior to what their small numbers might suggest. They were not the psychopaths, fanatics, or secret network of spies so common in the popular imagination. Rather, they were the linchpins in the inquisitional system that policed the orthodoxy of the Catholic flock and qualified candidates for inquisitional office. Joaquim Marques's career demonstrates that comissários had considerable room to manoeuvre, though they remained distinctly vulnerable to social and political shifts in power. His story reveals an institution divided against itself, which proved unwilling or unable to support its men in the field. Consequently, Joaquim Marques's attempts to protect himself and the Inquisition from attack proved futile. He died a defeated man on the eve of the political, intellectual, and spiritual upheaval he had long predicted and resisted. In Defence of the Faith is a study of the decline of the old regime and the rise of a new order in late-colonial Brazil as experienced by an unbending agent of a once powerful institution that slowly collapsed during his lifetime.