What is the "fideism" rejected by the Catholic Church?

In philosophy, [*fideism*](https://en.wikipedia.org/wiki/Fideism) seems to be used as a label to refer to epistemological approaches that tend to prioritize *faith* over *reason*. And this makes sense; after all, "fideism" is just Latin for "faith-ism." In the context of Catholic theology, *fideism* is a bad thing. John Paul II warned against "a resurgence of *fideism*" ([*Fides et ratio*](http://w2.vatican.va/content/john-paul-ii/en/encyclicals/documents/hf_jp-ii_enc_14091998_fides-et-ratio.html)) and Pius X links it to modernism in *[Pascendi Dominici Gregis](http://w2.vatican.va/content/pius-x/en/encyclicals/documents/hf_p-x_enc_19070908_pascendi-dominici-gregis.html)* . But it turns out that "fideism" is actually a very vague term, particularly so because it is frequently used pejoratively by opponents of certain belief systems. One person might be accused of fideism for believing that reason alone cannot demonstrate God's existence, while another might be accused of it for believing that reason alone cannot change a sinner's heart. The *Stanford Encyclopedia of Philosophy* gets to the heart of it: > Fideism claims that **truths of a certain kind** can be grasped only by foregoing rational inquiry and relying solely on faith. [[source](https://plato.stanford.edu/entries/fideism/) , emphasis added] Using this language, my question is: What are the "truths of a certain kind" found in the *fideism* rejected by the Catholic Church? Put another way: According to Catholicism, in what matters is it legitimate to prioritize faith over reason? For example, consider doctrines like: - the nature of the Trinity - The immaculate conception of Mary - The virgin birth of Jesus Christ - The descent of Jesus into Hades after his crucifixion - The real presence of Jesus in the Eucharist Are these doctrines thought to be discernible exclusively or primarily through *reason*? Or do they find their primary support in one's *faith* in the Scriptures and Tradition? **How does the Catholic Church define the *fideism* that it rejects?** I am particularly interested in direct quotes from papal encyclicals and official documents of the Vatican, particularly post-Vatican II.