"Fides" is the Latin word for "faith."
Fideists hold that there are no rational grounds for faith. They portray faith as blind obedience or a leap in the dark. Their faith is based solely on faith, not reason.
For Catholics, blind faith is a vice, not a virtue.
God created us as intelligent beings. Our powers of the intellect are part of being in the "image and likeness" of God (Gen 1:27-18). God is not offended by our thinking about what and why we believe. On the contrary, Peter tells us we should "always be ready to give an explanation [Greek: apologos] to anyone who asks you for a reason [Greek: logos--word, logic, reason, principle] for your hope" (1 Pet 3:15).
Jesus is the Logos. Jesus is the Logic of the universe. People want to teach the power of positive thinking. I'd like to teach the power of thinking--thinking faithfully. There is nothing more positive than the truth, but it's hard work to know the truth. Simple people, "the charcoal burners," rely on benevolent fideism. What is bad is malevolent fideism, anti-intellectualism.
Some of my students think that they are rejecting the Catholic faith when they refuse to believe blindly everything that the Church teaches. It's so sad. The Church also rejects "blind faith." It is true that there are moments in the spiritual life when we must endure a kind of darkness and step out in faith, without any assurance of what will happen as a consequence, but our basic belief in the existence, goodness, omnipotence, and omniscience of God is based on "natural theology," which, in turn, opens us to hear the proclamation of the gospel that God Himself has become human in order to save us from our sins. We have good reasons to believe that Jesus is true God and true man. The reasons are not "proof" in the strict sense, but they make the decision to believe a rational action that is perfectly in keeping with our intellectual nature.
The great problem is that so many of my students only think that they are thinking when, in fact, they are merely reacting and rationalizing. It is their faith in their own power of reason that is blind. :o(