Through the holy spirit for one.
In any event, Catholics consider Sacred Tradition to be the work of the Holy Spirit, and therefore on a par with Scripture, yet it is rejected across the board within Protestantism as being "extra-Biblical." How is our version of the "work of the Holy Spirit" inoperative and ipso facto rejected, while far more novel doctrines, mutually exclusive as noted previously, are given a free pass as "the work of the Holy Spirit"?
Hmmmm.... Evangelicals involved with extra-biblical revelation? Are you sure about that?