A senior Vatican investigator into clerical child sex abuse scandals in Ireland yesterday spoke of the Pope's determination that such evil does not happen again.
But Archbishop of Toronto Thomas Collins warned the congregation in Thurles Cathedral, Co Tipperary, that "even one priest gone wrong" caused immense harm, and that throughout the world priests had done unspeakable evil, sometimes at church events.
Archbishop Collins has been instructed by Pope Benedict XVI to conduct an inquiry into the Archdiocese of Cashel and Emly, and to submit a report on his findings to the Pontiff by Easter.
Speaking at a penitential service, Archbishop Collins said a practical way in which the Catholic Church could show its concern was by "doing all that we can to learn from this experience of evil, and so to try to be sure that it never happens again".
But he added that the evil of the sexual abuse of the young was all the more devastating when the perpetrators were priests.
"We cannot escape the horror of this by pointing out that the great majority of priests serve faithfully, with integrity and compassion," said Archbishop Collins.
"But even one priest gone wrong causes immense harm, and throughout the world priests have done unspeakable evil, sometimes within the very sacramental setting which should above all environments be most sacred and safe.
"But it is the sacred responsibility of us all, but most especially of the authorities in the church, to do what we can to prevent such evil, and to deal with it effectively whenever it is found.
"The crimes themselves, and the failure of church authorities to respond adequately to them, are both great scandals.
"We recognise the courage of the victims and their families who came forward and shone the cleansing light of truth on their suffering," he added.
Over the next few days Archbishop Collins will hold confidential meetings with abuse victims, and he has already held private discussions with 20 priests.