Here are list of the Dogma, FYI.
Having a very similar question, I will give you a reply from a friend,
A Catholic must believe in Purgatory, since it is a defined DOGMA of the Catholic Church. It is a dogma because it is both a de fide article of the Apostolic Deposit (the ancient and universal belief of the Church …not something new) and it was also dogmatically mandated by the Council of Ferrara-Florence and the Council of Trent. So, we do not have the freedom to reject Purgatory.
As for what a dogma is, as opposed to a doctrine … “Doctrine” is merely a formal (or informal) teaching of the Catholic Church. And, in Catholicism, we recognize three classifications of “doctrine”:
- Canon Law (or disciplines), and …
- Theolegoumena (or theological opinions).
Dogmas are those things which I must believe and must obey in order to be a Catholic (e.g. the Trinity or Purgatory).
Canon law are those things which I do not necessarily have to believe, but must obey in order to be a Catholic (e.g. the discipline of the celibate priesthood …a Catholic may believe that married men should be priests, but may not encourage his priest to marry, etc.).
And theolegoumena (or theological opinions) are those areas in which the Church has yet to take an official position, and so we have the freedom to choose between one position or another (e.g. the authorship of the Gospel of John, in which a Catholic is free to believe that John personally wrote it, or that it was dictated by John and someone else wrote it, or that John’s disciples wrote it, based on his oral traditions, after his death).
Most dogmas start out as theolegoumena (theological opinions) until the Church speaks formally on them. For example, the specific definition of the Trinity (that is, how to clearly state the organic and substantial belief of the Apostles) was a matter of debate in the Church until it was finalized, and dogmatized, at the Council of Nicaea.
As for Purgatory … Many English-speaking Christians (both Catholic and non-Catholic) are under the ridiculous impression that it is some kind of medieval invention of the Church and not the ancient and consistent belief of Apostolic Christians. So, here are some ancient Christians referring to it. Please note how they come from every part of the ancient Church, East and West, showing the universality of the doctrine:
(if any want the Early Church Fathers writings of Purgatory I will forward what I was given)