Catholics call the month of November the “month of holy souls.” It is our annual commemoration of the dead. The month begins with All Saints’ Day, which is our celebration of the citizens of Heaven. On the day after, All Souls Day, we remember all the dead, especially those whom we have known and loved, in the hope that they are destined to be citizens of Heaven. But we know that most of them have something to go through before they get there: We call it Purgatory. We believe that prayers and sacrifices offered for them here on earth will help them reach their destination—and help us too, strengthening our hope for them and for ourselves.

We are not so vain as to imagine that everyone we remember this month died a saint, perfect in love of God and neighbor; but we believe that those of them who died in grace, sorry for the ways they failed to love God and their neighbor, will be perfected by enduring Purgatory, and prepared to receive the gift of endless life and happiness in Heaven.

So, what is Purgatory? Before we answer that, we must ask the question, “What is death?” Or, to put it less abstractly, “What will it be like to die?”

Of course, we all will die. And we will experience death in different ways: suddenly, for example, by a fatal accident, heart attack, or stroke, or gradually, through a fatal disease. It can come to us in youth, or mid-life, or old age. We may see our death approaching as an enemy, or as a friend. But however it comes, however we anticipate it, death will be essentially the same for all of us: a final separation, final and definitive.

Death will be a final separation from this world that we inhabit, and know, and act in through our bodies. Everything and everyone that made up our lives here will be gone. We will be left with nothing but ourselves, for better or for worse. And the selves we will be left with—what we call our souls—will reflect free choices we have made all through life, up to and including our last minute. These choices, St. Augustine said, amount to just two kinds: those made out of love for ourselves in preference to God and neighbor, and those made out of love for God and neighbor in preference to ourselves.

The moment of final dissolution of our bodily bond with this world, the moment of our death, will be definitive—in the sense that we will be forever what we are just at that moment: people who have loved themselves in preference to God and neighbor, or people who have loved God and neighbor in preference to themselves.

Something that St. Thomas Aquinas called a “spiritual law of gravity” will be at work: According to their final state, our souls will gravitate either downward into themselves, or upward out of themselves. The person who has made himself the center of his choices will find himself forever in a miserable state of isolation. That is Hell. But the person who has made God and neighbor the center of his choices will find himself forever in a state of interpersonal communion, fellowship, and friendship—perfect mutual enjoyment. That is Heaven.

Our death will be final: There will be no going back to remake ourselves. The “spiritual law of gravity” will take us either to Heaven or to Hell. These are the only ultimate destinations for us human beings—either endless, perfect happiness, or endless, perfect misery. Every morally significant choice we make in our life here is a choice for Heaven or for Hell.

But wait: We who follow Christ believe that God is merciful. We know that in this life, at every moment until death, he offers us opportunities to change, to turn from self to Him and to our neighbor, to accept forgiveness and be reconciled. He gives us grace to remake ourselves. His mercy is the “spiritual gravity” that pulls us outward from ourselves and upward to Himself. His mercy operates on us continuously, calling us, inviting us to surrender ourselves, with all our imperfections, to Him who wants nothing better than to have us with Him in eternity, in perfect happiness and peace.

Therefore, we believe that the soul who at the moment of parting from the body prays, “Dear Lord, have mercy upon me, a sinner;” who prays with Jesus from the Cross, “Father, into your hands I commend my spirit”—we believe that soul is on its way to Heaven. The mercy of God continues to operate upon it even after death, preparing it for Heaven. That’s what Purgatory is: God’s mercy purging souls of the residue of sin; cleansing them from what remains of that attachment to self, that assertion of self, which once led them into sin. Purgatory is God’s mercy helping souls complete the self-surrender that was only partial at the moment of their death, so as to make them perfectly receptive to the joys of Heaven.

Purgatory is a state of suffering, indeed: We cannot know precisely what it feels like, but we can be sure it is the kind of suffering that leads to healing, like the suffering of rehabilitation or recovery. Its glorious end is always in view of the souls that must endure it, which makes all the difference. They can feel God’s mercy operating on them through their suffering; and I believe they can feel our prayers and sacrifices for them operating with God’s mercy, part of that tremendous “spiritual gravity” that is drawing them up to glory. Requiem aeternam dona eis Domine, et lux perpetua luceat eis: “Rest eternal grant unto them, O Lord, and let perpetual light shine upon them.”