In my current theology coursework, the question came up on how purgatory fits in with the four last things for mankind (death, judgement, heaven, hell).
Prior to The Fall, mankind was in a pre-sin state and always enjoyed God’s friendship. Man was created in a perfect state, fully mirroring God’s image. But due to the way sin effected what God meant for perfection, death entered in along with sin. Death was not initially part of the picture, but sin has a rotting effect on us.
Then because of sin and death, judgement was necessary. Even though Adam chose disobedience, and even though we inherited Original Sin, God allows each soul to decide which path to follow. He offers to us even in our imperfection the capability to seek the God from whom Adam and Eve turned. The ability to freely choose is a great gift. We have complete control over our decision; it is part of the dignity God gives us, so as not to be forced to love Him.
And with His judgement comes our deserved punishment or reward…eternal life or eternal damnation. But even if we are judged that we love God, our earthly lives generally cannot reach the purity God had first created in Adam and Eve. That was once only, and not available to their offspring after they were cut off from the Garden. And it may not seem fair, but how could God remove Adam and Eve from Eden due to sin, then bring offspring of the sinful back to a place of purity?
His final solution was One who could re-direct the soul of all mankind. Christ moved in the hearts of the sinful line from Adam and Eve with a path back toward God. And even though we have an inherited propensity to sin, after death God reclaims and renews the sinful nature born into those who truly love Him so that the perfection that was impossible on the earth Adam wrought is made possible in God’s gift of purgatory. Purgatory is then the temporary, intermediate stopping place for those judged worthy and destined for heaven, though in need of further preparation.
No one desires pain. And we know that with purgatory, we will suffer some form of pain and loss. But with that experience is hope and sureness of our final heavenly destination. So for the majority of the faithful who die in a less than perfect state (and that truly is most of us), purgatory is a welcome rest stop on the journey home.