History of the belief
Image of a non-fiery purgatory (Gustave Doré: illustration for Dante's Purgatorio, Canto 24).
While use of the word "purgatory" (in Latin purgatorium) as a noun appeared perhaps only between 1160 and 1180, giving rise to the idea of purgatory as a place (what Jacques Le Goff called the "birth" of purgatory), the Roman Catholic tradition of purgatory as a transitional condition has a history that dates back, even before Jesus Christ, to the worldwide practice of caring for the dead and praying for them and to the belief, found also in Judaism, which is considered the precursor of Christianity, that prayer for the dead contributed to their afterlife purification. The same practice appears in other traditions, such as the medieval Chinese Buddhist practice of making offerings on behalf of the dead, who are said to suffer numerous trials. Roman Catholic belief in after-life purification is based on the practice of praying for the dead, which is mentioned in 2 Maccabees 12:42-44, what the Roman Catholic Church has declared to be part of Sacred Scripture, and which, according to the Catechism of the Catholic Church, was adopted by Christians from the beginning, a practice that presupposes that the dead are thereby assisted between death and their entry into their final abode.
Shortly before becoming a Roman Catholic, the English scholar John Henry Newman argued that the essence of the doctrine is locatable in ancient tradition, and that the core consistency of such beliefs is evidence that Christianity was "originally given to us from heaven". Roman Catholics consider the teaching on purgatory, but not the imaginative accretions, to be part of the faith derived from the revelation of Jesus Christ that was preached by the Apostles. Of the early Church Fathers, Origen says that "He who comes to be saved, comes to be saved through [a] fire" that burns away sins and worldliness like lead, leaving behind only pure gold. St. Ambrose of Milan speaks of a kind of "baptism of fire" which is located at the entrance to Heaven, and through which all must pass, at the end of the world. Pope St. Gregory the Great says that the belief in purgatory is "established" (constat) and "to be believed" (credendum), insisting, however, that the purgatorial fire can only purify away minor transgressions, not "iron, bronze, or lead" or other "hardened" (duriora) sins. By this he meant that attachments to sin, habits of sin, and even venial sins could be removed in purgatory, but not mortal sin, which, according to Catholic doctrine, causes eternal damnation. Over the centuries, theologians and other Christians then developed the doctrine regarding purgatory, leading to the definition of the formal doctrine (as distinct from the legendary descriptions found in poetic literature) at the First Council of Lyon (1245), the Second Council of Lyon (1274), the Council of Florence (1438–1445), and the Council of Trent (1545–63).