You said that St. Paul taught the doctrine of purgatory
I believe my original response was "Paul taught purgatory?" with the implied question "where?" I was asking for Biblical evidence ... which you graciously provided.
You choose 1 Cor 3; which talks about judgment of works and you used that passage to claim that purgatory is what Paul is talking about. I highlighted at least 5 problems with the interpretation you espouse and you started to address maybe one of them. You made the claim that purgatory is not punishment, but merely some kind of preparation.
Then I showed you in your own catechism where the concept of atonement in purgatory (not merely some preparation) is clearly laid out, and your desire was then to play word games ... claiming that expiation does not mean atonement.
There is no shame in admitting that your religion teaches you are making atonement for your own sins in purgatory ... 1475 clearly teaches that ...
Let me highlight it again for you ... and perhaps you can find another way to explain it.
1475 In the communion of saints, "a perennial link of charity exists between the faithful who have already reached their heavenly home, those who are expiating their sins in purgatory and those who are still pilgrims on earth. between them there is, too, an abundant exchange of all good things." In this wonderful exchange, the holiness of one profits others, well beyond the harm that the sin of one could cause others. Thus recourse to the communion of saints lets the contrite sinner be more promptly and efficaciously purified of the punishments for sin.
So here is the position you are now in ... By holding to the doctrine of purgatory, you are trusting in your own ability (and other saints) to atone for your sins in purgatory. With that position ... you are spitting on the sacrifice of the Son of God ... in fact claiming that you must pay for your own sins in purgatory, with the theological consequence that the atoning work of the Lord of Glory is not enough.
What exactly is your faith and trust in? The atoning work of Jesus Christ ... or the doctrine of the RCC?
If it is Jesus Christ and His work on the cross ... then you must reject the doctrine of purgatory as both unbiblical and contrary to sound doctrine. If it is in the doctrine of the RCC, then you willingly invite eternal consequences for your error ... for to have a misunderstanding concerning the atoning work of Christ demonstrates that you have in fact synthesized a god in the image of the RCC, rather than the God of the Bible. This amounts to idolatry ... and you risk a judgment day pronouncement ... "Depart from Me ... I never knew you"
If you want to know how our works participate in the atonement of Christ, there is a catechism for that as well, but it has nothing to do with purgatory (souls in purgatory cannot participate in the sacrifice of Christ because they cannot do any works; nor do they need it because they have already been saved).
Here is what the Church teaches on the unique atonement of Christ and how the living on this earth can participate in the sacrifice of Christ:
Jesus consummates his sacrifice on the cross
616 It is love "to the end"446 that confers on Christ's sacrifice its value as redemption and reparation, as atonement and satisfaction. He knew and loved us all when he offered his life.447 Now "the love of Christ controls us, because we are convinced that one has died for all; therefore all have died."448 No man, not even the holiest, was ever able to take on himself the sins of all men and offer himself as a sacrifice for all. the existence in Christ of the divine person of the Son, who at once surpasses and embraces all human persons, and constitutes himself as the Head of all mankind, makes possible his redemptive sacrifice for all.
617 The Council of Trent emphasizes the unique character of Christ's sacrifice as "the source of eternal salvation"449 and teaches that "his most holy Passion on the wood of the cross merited justification for us."450 and the Church venerates his cross as she sings: "Hail, O Cross, our only hope."451
Our participation in Christ's sacrifice
618 The cross is the unique sacrifice of Christ, the "one mediator between God and men".452 But because in his incarnate divine person he has in some way united himself to every man, "the possibility of being made partners, in a way known to God, in the paschal mystery" is offered to all men.453 He calls his disciples to "take up [their] cross and follow (him)",454 for "Christ also suffered for (us), leaving (us) an example so that (we) should follow in his steps."455 In fact Jesus desires to associate with his redeeming sacrifice those who were to be its first beneficiaries.456 This is achieved supremely in the case of his mother, who was associated more intimately than any other person in the mystery of his redemptive suffering.457 Apart from the cross there is no other ladder by which we may get to heaven.458
446 ⇒ Jn 13:1.
447 Cf. ⇒ Gal 2:20; ⇒ Eph 5:2, ⇒ 25.
448 ⇒ 2 Cor 5:14.
449 ⇒ Heb 5:9.
450 Council of Trent: DS 1529.
451 LH, Lent, Holy Week, Evening Prayer, Hymn Vexilla Regis.
452 1 Tim 2:5.
453 GS 22 # 5; cf. # 2.
454 ⇒ Mt 16:24.
455 I Pt 2:21.
456 Cf ⇒ Mk 10:39; ⇒ Jn 21:18-19; ⇒ Col 1:24.
457 Cf. ⇒ Lk 2:35.
458 St. Rose of Lima: cf. P. Hansen, Vita mirabilis (Louvain, 1668).
So what is your religion, if I may ask, that is "not Protestant" yet surpisingly repeats every canard about the purgatory and atonement that the Protestans use to spread their lies?