Prophecy is a charism, a spiritual gift given by the Holy Spirit to some members of the Church. It is not difficult to understand how it works. It puzzles me how Catholics can have such varying opinions on it.
I had a long online discussion with a blogger I had read and admired for years. He recently wrote a post on the unapproved apparitions in Garabandal, Spain, suggesting that there would be a miraculous event that the world would see in April of 2017. Because of some positive statements on the apparitions by some Spanish Bishops and from Rome he felt that the apparitions would soon be approved.
I argued that there were inconsistencies in the messages. This went back and forth and he became rather uncharitable. Then Joey Lomagino died. He was the blind guy who the seers said would miraculously regain his sight just before the miraculous event. He never did. The lesson: until a Marian apparition is approved, it is not approved. Simple. What a waste of time!
Then there are those who completely disparage prophecy. I recently commented on a blog post which insisted that reading about private revelations is a waste and should be avoided. I brought up Hildegard, her relationship to Pope Eugenius III, and the authenticity of her visions. I was scolded and told that I should be reading the writings of saints and Doctors of the Church. I mentioned that Hildegard is a saint and a Doctor of the Church.
St. Paul makes it clear:
Do not despise prophesying, but test everything; hold fast what is good. (1 Thessalonians 5:20-21)
If God wants us to discern the authenticity of a prophecy then it implies that it could be done. He would not tell us to do something that we are not able to do. We use our minds and the guidance of the Church, who approves some instances of private revelation and condemns others. She also makes a judgment on those who claim the gift when she makes them saints. Benedict XVI new very well that Hildegard wrote down many of her prophetic visions when he elevated her works to the level of St. Thomas Aquinas and St. Augustine by making her a Doctor of the Church. These writings are not perfect, but very worthy of study.