The scientific and religious discussions and debates about the origins of the image that Pia photographed continued. On the religious front, in 1939 Pia's negative image was used by Sister Maria Pierina De Micheli, a nun in Milan, to coin the Holy Face medal, as part of the Catholic devotion to the Holy Face of Jesus. Pope Pius XII approved the devotion and the medal and in 1958 declared the Feast of the Holy Face of Jesus as Shrove Tuesday (the Tuesday before Ash Wednesday) for all Roman Catholics. On the occasion of the 100th year of Secondo Pia's first photograph, on 24 May 1998, Pope John Paul II visited Turin Cathedral. In his address on that day, he said, "the Shroud is an image of God's love as well as of human sin", and he called the shroud "an icon of the suffering of the innocent in every age".