Thought is either rational, or it's not. All else is irrelevant.
Rationalism, and its close cousin modernism, are considered heresies by the Church. When one breaks down the essential difference between Catholicism and Protestantism, we see that the breakdown lies between reason derived from faith for the Catholic, and faith determined by reason for the Protestant. The Catholic believes God based on the living authority and living Voice (The Holy Spirit) He gave to those chosen to spread the Gospel. The Catholic believes that man has the capacity to comprehend the infallible Word of God by his reason, but his reason does not determine what he will and will not believe. Faith is an act of the will.
The Protestantism which puts man’s intellect and individual rational capacity above and before faith. Most Protestants will not believe what does not make sense to them. Although most Protestants will profess Sola Fide, it is not really faith in God they are living by, but only faith in themselves and their cognitive abilities. For the Catholic, faith precedes reason, for the Protestant, reason precedes faith.
Simply put, the Protestant takes God’s Written Word and attempts as best as he can to determine what it means for him, and then put his faith in what he has determined. He bases his faith off of what he reads in and into the Scriptures and determines for himself the doctrines he will believe. This is completely the opposite of Catholicism position, which simply listens to God’s voice speaking through His one and only Church, and then seeks to understand that faith by his reason.
Peace be with you