The Catholic position on praying for the dead stands on two other doctrines: the teachings on purgatory and the communion of saints. First, purgatory. It's best described as a condition—not a place—between death and heaven. Notice that it's not between heaven and hell, as many folks presume. There's no chance that a person in need of preliminary purification can ever be lost. If a person were lost, they'd already be in hell.

The church teaches that remarkably few people are so holy that they can attain heaven in one leap or so irreconcilably evil that they wind up straight in hell. The deliberate choice to turn from God and grace and not to look back is rarely made, and in any case it's not for us to judge. So what's left for us is to pray for all who go before us in death, especially those known to us personally.

Our belief in the communion of saints is an acknowledgment that death doesn't break the bonds of our relationship to one another. The holy ones are praying for us, and we are praying for the less-than-holy-ones still working out the details of their journey to total union with God. Because God is love, anything unloving has to be left behind for that union to take place. In the "economy of salvation," the currency we use to assist our friends is prayer.

Praying for the dead means more than only saying prayers for them. It can include offering a Mass for their sake, giving alms in their name, or any good work performed for their intention. And should we do these things for bad people, even really bad ones who may have hurt us? Those folks more than any others need our help! Jesus tells us to love our enemies and to bless those who injure us. Certainly we can bless others in death as well as in life.

Praying for the dead is an ancient practice. The Jewish community was doing it two centuries before Christ, as evidenced in the Second Book of Maccabees. Inscriptions in the catacombs of the first five centuries, not to mention ancient liturgies of the church, testify that early Christians fervently followed this practice. Those who have gone before us need our prayers. And someday we will likely need prayers ourselves.

Scripture
2 Maccabees 12:38-46; Luke 6:27-36, 37-42

Online resource
Father Ron Rolheiser, O.M.I. on "Praying for the Dead"

Book
Praying for the Dead: A Holy and Pious Thought by Michael Miller (Our Sunday Visitor: 1994)

Pamphlet
Praying for the Dead (Catholic Truth Society, 2008)