18 Then Moses said, “Now show me your glory.”
19 And the Lord said, “I will cause all my goodness to pass in front of you, and I will proclaim my name, the Lord, in your presence. I will have mercy on whom I will have mercy, and I will have compassion on whom I will have compassion. 20 But,” he said, “you cannot see my face, for no one may see me and live.”
The Catechism of the Catholic Church defines purgatory as a “purification, so as to achieve the holiness necessary to enter the joy of heaven,” which is experienced by those “who die in God’s grace and friendship, but still imperfectly purified” (CCC 1030). It notes that “this final purification of the elect . . . is entirely different from the punishment of the damned” (CCC 1031).
The purification is necessary because, as Scripture teaches, nothing unclean will enter the presence of God in heaven (Rev. 21:27) and, while we may die with our mortal sins forgiven, there can still be many impurities in us, specifically venial sins and the temporal punishment due to sins already forgiven.
When we die, we undergo what is called the particular, or individual, judgment. Scripture says that “it is appointed for men to die once, and after that comes judgment” (Heb. 9:27). We are judged instantly and receive our reward, for good or ill. We know at once what our final destiny will be. At the end of time, when Jesus returns, there will come the general judgment to which the Bible refers, for example, in Matthew 25:31-32: “When the Son of man comes in his glory, and all the angels with him, then he will sit on his glorious throne. Before him will be gathered all the nations, and he will separate them one from another as a shepherd separates the sheep from the goats.” In this general judgment all our sins will be publicly revealed (Luke 12:2–5).
Augustine said, in The City of God, that “temporary punishments are suffered by some in this life only, by others after death, by others both now and then; but all of them before that last and strictest judgment” (21:13). It is between the particular and general judgments, then, that the soul is purified of the remaining consequences of sin: “I tell you, you will never get out till you have paid the very last copper” (Luke 12:59).