Ex opere operato

Eamon Duffy in seinem London Review of Books-Review von Joseph Leo Koerner: The Reformation of the Image:

"Koerner here effectively articulates a modern version of an accusation often made by Lutherans at the time of the Reformation: Catholicism was external, magical and mechanical, Protestantism was interior and rooted in personal responsibility. Reformation polemic is thus recycled as considered historical generalisation. As a description of medieval sacramental belief, however, it is quite simply mistaken. The medieval Church's insistence that the sacraments worked ex opere operato was a claim about the dependable availability of God's grace, but emphatically not a guarantee that grace would be effective for the recipient regardless of interior disposition.

Essentially, the doctrine guaranteed the spiritual lives of ordinary people against wicked or inadequate priests. Mass might be celebrated by a saint, or by a clerical philanderer still reeking from his mistress's or his boyfriend's bed: but provided both had been duly ordained, and used the correct prayers, Christ would be just as truly present at the sinner's Mass as at the saint's. However, that presence, stupendous mystery as it was, was in itself no guarantee of benefit, either to celebrant or congregation. Medieval Catholics, just like 16th-century Protestants, thought that an unworthy or inattentive communicant not only received no blessing from the eucharist, but on the contrary ate and drank damnation. Christ was objectively present even to the wicked; but the inner spiritual power and healing of the sacrament was available only to devout penitence and faith."