There are key concepts of Catholic dogma and doctrine that are not explicitly mentioned in the scriptures. However, these concepts can be reasoned from various elements of scripture. This reasoning must be logical and result in a prudent conclusion.
In the case of Purgatory, we first consider the Book of Revelation Chapter 21, speaking of Heaven states:
27 But nothing unclean will enter it…
Also, Hebrews chapter 5 states:
22 But you have come to Mount Zion and to the city of the living God, the heavenly Jerusalem, and to innumerable angels in festal gathering, 23 and to the assembly of the firstborn who are enrolled in heaven, and to God the judge of all, and to the spirits of the righteous made perfect…
Again, Hebrews 11 brings up this concept of being “made perfect”:
39 Yet all these, though they were commended for their faith, did not receive what was promised, 40 since God had provided something better so that they would not, apart from us, be made perfect.
There are two key points to be made based upon these scripture verses. First, nothing unclean shall enter Heaven. Second, “the spirits of the righteous [will be] made perfect.” (Hebrews 5: 23) The phrase “made perfect” implies some process must exist. Catholics call this process Purgatory.
There are two items that must be cleansed in Purgatory for us to be made perfect. First, we must be cleansed from material wants that we use as substitutes for God. These material wants, as defined by St. Thomas Aquinas are wealth, pleasure, power, and honor. (Summa II-I, Q. 2) As a junky must go through some level of detoxification to be cleansed, we must also be detoxified from these material wants. In this regard, we read in 1 Peter 4:
1Since therefore Christ suffered in the flesh, arm yourselves also with the same intention (for whoever has suffered in the flesh has finished with sin), 2 so as to live for the rest of your earthly life no longer by human desires but by the will of God.
Second, while we have sinned against God, in some cases we have also sinned against another person. This sinning against another person is associated with temporal punishment. When we go to confession we can receive God’s forgiveness, but the temporal punishment remains.
An example of receiving God’s forgiveness, but still incurring temporal punishment can be seen in 2 Samuel 12. King David sinned with respect to his infidelity with Bathsheba. Nathan, the prophet confronted David:
13 David said to Nathan, “I have sinned against the Lord.” Nathan said to David, “Now the Lord has put away your sin; you shall not die. 14 Nevertheless, because by this deed you have utterly scorned the Lord, the child that is born to you shall die.”
David repented and received forgiveness for his sin, yet the child still died.
Jesus makes reference to temporal punishment and how to avoid it in Luke 12:
57 “And why do you not judge for yourselves what is right? 58 Thus, when you go with your accuser before a magistrate, on the way make an effort to settle the case, or you may be dragged before the judge, and the judge hand you over to the officer, and the officer throw you in prison. 59 I tell you, you will never get out until you have paid the very last penny.”
The good news is that we are assured Heaven after Purgatory. 1 Corinthians 3 reads:
13 the work of each builder will become visible, for the Day will disclose it, because it will be revealed with fire, and the fire will test what sort of work each has done. 14 If what has been built on the foundation [Jesus] survives, the builder will receive a reward. 15 If the work is burned up, the builder will suffer loss; the builder will be saved, but only as through fire.
Fire—in this context—refers to a transformation from one state to another and is a form of cleansing.
In conclusion, Purgatory does not exist because of God’s anger, but because of God’s love and His desire for us to be with Him in Heaven. Purgatory is the means by which we are purified and “made perfect” so that we can enter into Heaven where nothing unclean is permitted.