Here’s a quote from the last of P. Canalemessa’s three advent homilies:
In [a] university sermon entitled “Faith and Reason in Confrontation,” Newman illustrates why reason cannot be the last judge in matters of religion and faith, with the analogy of the conscience: “No one will say that conscience is against reason, or that its dictates cannot be thrown into an argumentative form; yet who will, therefore, maintain that it is not an original principle, but must depend, before its acts, upon some previous processes of reason? Reason analyzes the grounds and motives of action: a reason is an analysis, but is not the motive itself. As then conscience is a simple element in our nature, yet its operations admit of being surveyed and scrutinized by reason; so may faith be cognizable, and its acts be justified, by reason, without therefore being, in matter of fact, dependent upon it. […] When the Gospel is said to require a rational faith, this need not mean more than that faith is accordant to right reason in the abstract, not that it results from it in the particular case.”
Newman’s analysis has new and original features; he brings to light the so to speak imperialist tendency of reason to subject every aspect of reality to its own principles. One can, however, consider rationalism also from another point of view, closely connected with the preceding one. To stay with the political metaphor used by Newman, we can describe it as the attitude of isolationism, of reason’s shutting itself in on itself. This does not consist so much of invading the field of another, but of not recognizing the existence of another field outside its own. In other words, in the refusal that some truth might exist outside that which passes through human reason.
Rationalism was not born in this guise with the Enlightenment, even if it impressed on it an acceleration whose effects still persist. It is a tendency against which the faith has always had to struggle. Not only the Christian faith, but also the Jewish and Islamic faiths, at least in the Middle Ages, were faced with this challenge.
Raised in every age against such a pretext of the absolutism of reason, has been the voice not only of men of faith but also of militant men, philosophers and scientists, in the field of reason. “The supreme act of reason,” wrote Pascal, “lies in recognizing that there is an infinity of things that surpass it.” In the very instant that reason recognizes its limit, it breaks it and exceeds it. It is the work of reason that produces this acknowledgment, which is therefore an exquisitely rational act. It is, to the letter, a “learned ignorance,”  a knowing of not knowing.
It must be said, therefore, that the one who puts a limit to reason and humiliates it is rather the one who does not recognize the capacity it has to transcend itself. “Up until now,” wrote Kierkegaard, “one has always spoken thus: ‘To say that this or that thing cannot be understood does not satisfy science which wants to understand.’ Here is the mistake. In fact, the contrary should be said: If human science does not want to acknowledge that there is something that it cannot understand, or — in a still more precise way — something of which with clarity it can understand that it cannot understand, then everything is thrown into confusion. Hence it is a task of human knowledge to understand that there are and which are the things that it cannot understand.”