Let us grant, however, that all this might have been tolerated for a time as a thing of no great moment; yet when the expiation of sins is sought elsewhere than in the blood of Christ, and satisfaction is transferred to others, silence were most perilous. We are bound, therefore, to raise our voice to its highest pitch, and cry aloud that purgatory is a deadly device of Satan; that it makes void the cross of Christ; that it offers intolerable insult to the divine mercy; that it undermines and overthrows our faith. For what is this purgatory but the satisfaction for sin paid after death by the souls of the dead? Hence when this idea of satisfaction is refuted, purgatory itself is forthwith completely overturned. But if it is perfectly clear, from what was lately said, that the blood of Christ is the only satisfaction, expiation, and cleansing for the sins of believers, what remains but to hold that purgatory is mere blasphemy, horrid blasphemy against Christ?
-- John Calvin, Institutes (3.5.6)
