Coming just after Hell and just before Heaven, the second of the three books that make up Dante's "Divine Comedy" is the "Purgatorio" -- Purgatory. In its ninth canto, Dante places these words in the mouth of the angelic guardian of Purgatory's gate who, displaying his keys, tells his listeners:

I hold them from St. Peter -- who bade me err

Rather in opening than shutting out.

In the poem, as in the teaching of the Church, Purgatory can only properly be understood as an expression of God's boundless mercy. For this is not a place of punishment but a place where, as a consequence of the divine generosity, repentant sinners are made ready to enter Paradise.

While the calendar of the Church contains no feast of Purgatory as such, we have its equivalent instead. It falls on Nov. 2, just after the feast of All Saints, and is called All Souls Day. This is when the Church encourages us to pray especially for our departed ones -- spouses, children, family members, friends, and many others -- who we believe, and hope are most likely now in Purgatory. This year, we might even say a prayer for Dante, the 700th anniversary of whose death we marked a few weeks ago.

The Catechism of the Catholic Church gives this succinct statement of the doctrine of Purgatory: "All who die in God's grace and friendship, but still imperfectly purified, are indeed assured of their eternal salvation; but after death they undergo purification, so as to achieve the holiness necessary to enter the joy of heaven" (CCC 1030).

Besides natural concern for loved ones, self-interest should move us to heed the prospect of Purgatory for ourselves. As St. John Henry Newman points out, "in one sense, all Christians die with their work unfinished." Purgatory is where the finishing touches are added.

Newman made that point in one of his Anglican sermons, "The Intermediate State." Like many non-Catholics, before his conversion he was hesitant about the idea of Purgatory as such, but he already recognized the need for a "time of maturing" between death and heaven and regarded it as "a great consolation" for anyone who thinks seriously about such matters.

Today, as then, there are two large reasons to do just that.

One has to do with the apparently large number of people who, says Newman, are either negligent, unrepentant, or foolishly certain of a death-bed conversion to see them through in the end. The Church does such people an immense kindness by now and then calling their attention to the traditional Last Things -- which include Heaven and Hell along with Purgatory.

The other great reason for remembering those in Purgatory whom we call the "Holy Souls" has to do with our serious duty to lend them a hand by prayer and penance, just as we hope others will do for us when the time and need come. St. Catherine of Genoa (1447-1510), a saint famous for her self-sacrificing services to the sick and poor as well as for her mystical experiences, put it this way in her treatise on Purgatory:

"The Almighty is so pure . . . That if a person is conscious of the least trace of imperfection and at the same time understands that Purgatory is ordained to do away with such imperfections, the soul enters this place of purification glad to accept so great a mercy of God.

"The worst suffering of these suffering souls is to have sinned against divine Goodness and not to have been perfected in this life."

- Russell Shaw is the author of more than twenty books. He is a consultor of the Pontifical Council for Social Communications and served as communications director for the U.S. Bishops.