Abstract from the "Treatise on Purgatory"
I believe no happiness can be found worthy to be compared with that of a She saw with the eyes of her soul and understood the condition of the faithful in the Purgatory; they were there to purify themselves before being introduced to God, in Paradise..
Treatise on the Purgatory of Saint Catherine from Genoa
The rust of the sin is the impediment, and the fire consumes the rust; in this way the soul is more and more subjected to the divine influence...
It is in this way that rust, which is sin, covers souls, and in Purgatory is burnt away by fire; the more it is consumed, the more do the souls respond to God, the true sun. As the rust lessens and the soul is opened up to the divine ray, happiness grows; until the time be accomplished the one wanes and the other waxes. Pain however does not lessen but only the time for which pain is endured. As for will: never can the souls say these pains are pains, so contented are they with God's ordaining with which, in pure charity, their will is united.
But, on the other hand, they endure a pain so extreme that no tongue can be found to tell it, nor could the mind understand its least pang if God by special grace did not show so much. Which least pang God of His grace showed to this Soul, but with her tongue she cannot say what it is.
Thence is born a raging fire, like that of Hell save that guilt is lacking to it. Guilt it is which makes the will of the damned in Hell malignant, on whom God does not bestow His goodness and who remain therefore in desperate ill will, opposed to the will of God.
O how dangerous is sin committed in malice! Hardly does a man repent him thereof, and without repentance he will bear its guilt for as long as he perseveres, that is for as long as he wills a sin committed or wills to sin again.
No tongue can tell nor explain, no mind understand, the grievousness of Purgatory. But I, though I see that there is in Purgatory as much pain as in Hell, yet see the soul which has the least stain of imperfection accepting Purgatory, as I have said, as though it were a mercy, and holding its pains of no account as compared with the least stain which hinders a soul in its love.
When with its inner sight the soul sees itself drawn by God with such loving fire, then it is melted by the heat of the glowing love for God, its most dear Lord, which it feels overflowing it. And it sees by the divine light that God does not cease from drawing it, or from leading it, lovingly and with much care and unfailing foresight, to its full perfection, doing this of His pure love.
These rays purify and annihilate.
What the man judges in himself perfection, it is defect with respect to God: whatever seems to be concerned with perfection, whatever he sees, he feels, he means, he wants, he remembers without recognising that it comes from God, it contaminates him.
It is true that love for God which fills the soul to overflowing, gives it, so I see it, happiness beyond what can be told, but this happiness takes not one pang from the pain of the souls in Purgatory.
Rather the love of these souls, finding itself hindered, causes their pain; and the more perfect is the love of which God has made them capable, the greater is their pain.
I would fain send up a cry so loud that it would put fear in all men on the earth. I would say to them: 'Wretches, why do you let yourselves be thus blinded by the world, you whose need is so great and grievous, as you will know at the moment of death, and who make no provision for it whatsoever?'
You have all taken shelter beneath hope in God's mercy, which is, you say, very great, but you see not that this great goodness of God will judge you for having gone against the will of so good a Lord.
Cease to hug yourselves, saying: I will confess my sins and then receive plenary indulgence, and at that moment I shall be purged of all my sins and thus shall be saved.
Think of the confession and the contrition needed for that plenary indulgence, so hardly come by that, if you knew, you would tremble in great fear, more sure you would never win it than that you ever could.