Some time ago, I wrote an explanation and defense of speculative theology and speculative eschatology, which I included in my book ‘The Secrets of Medjugorje and Garabandal Revealed’ as chapter III.7. That chapter is also available as a free PDF booklet:
On Speculative Theology and Eschatology [free PDF]
The booklet stands on its own as an explanation of the three types of ideas in Catholicism:
1. infallible doctrine (dogma)
2. non-infallible doctrine
3. fallible theological opinion (speculative theology)
The faithful need all three in order to live the Faith.
In the booklet, I also defend my speculative theology, which is fallible and has erred many times on the question of when events will occur. And I defend eschatology in general, which is an essential part of the Gospel of Jesus Christ.