Heaven and Hell, settled in 1336
The most important single document is the constitution Benedictus Deus, issued by Pope Benedict XII in 1336. It taught that the souls of the saints who need no purification see the divine essence, God Himself, immediately after death, and that those who die in actual mortal sin go down to Hell at once. This settled a dispute that had been simmering, whether the dead wait for the Last Judgment before seeing God. The Church answered no. The vision of God is given at once to those who are ready.
The Council of Florence, a century later, repeated that doctrine in its decree: the souls of the perfect are received immediately into Heaven, the souls of those who die in mortal sin or original sin alone go down to Hell, and the souls of the penitent not yet purified are cleansed first.
Purgatory as the third thing
Putting those together, you can see where Purgatory belongs in the Church's teaching. It isn't a separate verdict. It's a stage between the particular judgment and Heaven, for souls whose destination is already settled. The Catechism says it exactly: Heaven immediately, or Heaven after a purification, or everlasting damnation (CCC 1022).
The Church in three states
The Second Vatican Council gave the picture a new framing in Lumen Gentium. The Church, it says, is one family in Christ with three parts: some of His disciples are still pilgrims on earth, some have died and are being purified, and some are already in glory, gazing on God (Lumen Gentium 49). The living and the dead aren't separate worlds. They're one body, and the bond of love between them continues.
The same document says something that cuts against a popular idea. Our life on earth is lived once, and we won't come back to other earthly lives (Lumen Gentium 48). There's no reincarnation. The Church treats this as part of taking life seriously: each day is a real opportunity.
What stays open
As we've seen, the Church holds firm on these basics and stays silent on others: where, how long, how the fire works, who is in which state. Her teaching on the three destinations stays modest and clear, and that clarity is a gift. It means a person can live with confidence in what's certain without being tormented by what isn't.
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