St. John Cardinal Newman

Cardinal Newman has been canonized. He may well be the most theologically influential convert to Catholicism. 

Newman was a man of many parts. He has interesting things to say about the nature of miracles. And his illative sense made an important contribution to religious epistemology. He stressed the value of tacit knowledge. He objected to armchair epistemologies. He was interested in how people actually come to believe what they do, and the kinds of evidence that contribute to belief formation. An often unconscious process with a cumulative effect.  

Newman was an original and independent thinker. Because he converted to Catholicism, he had a different approach than if he'd been a trained Catholic theologian. His center of gravity was patristic theology rather than Scholastic theology. And he represents an offshoot of British Empiricism. 

There's nothing distinctive Catholic about the illative sense. That can be incorporated into a Protestant epistemology or secular epistemology. 

As Benjamin King has documented in Newman and the Alexandrian Fathers, Newman is apt to use the church fathers as a mirror, where he's gazing at his own reflection. Newman resembles Luther inasmuch as both developed one-man belief-systems to resolve their personal religious quest. These are answers to their questions, which arise from their individual struggles. 

Newman's primary impact on Catholic theology lies in his theory of development. Historically, Catholicism takes the position that the era of public revelation terminated with the death of the Apostles. They left behind the deposit of faith. That's static. You can appeal to ancient tradition as a witness to the deposit of faith. But you can't add to the deposit of faith and you can't change dogma.

The theory of development was necessitated by the increasing strain between the appeal to tradition and innovations in Catholic theology. Innovations that lacked a documentable pedigree in primitive tradition. 

Newman replaced the static concept of tradition with a fluid concept. No longer grounded in primitive tradition but "living" tradition. This would have remained an idiosyncratic curiosity except that it was adopted by Vatican II. 

The increasing strain between tradition and innovation was like metastatic cancer. The theory of development was like cancer therapy. But there's a catch. Sometimes cancer therapy prevents a patient from dying of cancer: instead, the patient dies from complications due to cancer therapy. The therapy does so much damage that the cure kills the patient.

The theory of development solved one problem by creating another problem. It severed Catholic theology from any traditional moorings. Catholic theology is now adrift. It has no fixed center or boundaries. Catholic theology is now the theology of whoever the current pope happens to be. Like a chameleon, Catholic theology changes colors to match the shade of the current pope.