Is faith irrational? Is Christianity anti-reason? Is it even possible to maintain a faith in God or in Christianity in the midst of this modern world? Opponents today say that believing in something that you cannot see or verify for yourself is the very definition of irrational behavior, especially if you are supposed to stake your entire life on the very thing you cannot see. But I think that the opponents of belief greatly misunderstand the right and proper relationship between faith and reason, and furthermore, they aren't even close to being correct when they say it is irrational to believe in something one does not see for oneself.
I would answer that quite the opposite is true: almost all human activity, learning, and life depends on belief.
You and I go about our daily lives in a largely faith-based world. What does that mean? I have a rough idea how an elevator works, but I have never personally met and certified every engineer, installer, inspector, and maintenance crew that worked on every elevator I’ve entered. Yet, I get into small metal boxes and that take me dangerously high. I trust the process and people, even though I have no clue what the process is, or how competent the people are that maintain these elevators. Does this make me irrational?
Or would it be irrational for me to stand in the lobby of some hotel demanding to meet the engineer and maintenance crews before I stepped foot in the elevator? Imagine seeing me, stomping my foot and yelling at the front desk, "I will never step one foot in this deathtrap until I see for myself the engineer is qualified and that every maintenance worker did her job!" I'm sure if you saw me carry on in such a manner, you would think I would have lost my mind. But why?
Daily human experience of elevators, planes, trains and automobiles have taught us over the decades that almost all of these things are reliable almost all the time. I know rationally that elevators do break, planes have fallen from the sky, trains have flown off their tracks, and cars have crashed. But I also know of the great majority of cases where nothing bad has happened. Maybe experience has taught us not to trust the shady looking amusement park's rusty rollercoaster, but surely not every rollercoaster is a flip of the coin whether one lives or dies.
This is the realm of belief. You have reasons to believe a thing is trustworthy regardless of whether or not you have seen it for yourself. You have seen enough to know that the Hilton will not tolerate elevators that kill their patrons. So even though you have never met the engineers or maintenance crews of that elevator, and even if you have no clue how an elevator works, you and I can hop on without a thought of it being unsafe because we believe it to be so.
Now we have arrived at something like a definition of belief. It is neither ignorance nor opinion, but rather belief is my ability to share in, to participate in, anther's knowledge. Put simply, reason sees truth for itself; whereas belief shares in what another has seen to be true. Reason is "seeing for oneself." Belief is "hearing what an eyewitness has seen."
But belief has one more quality that is necessary for it to be real: trust. You have to trust that the one who has seen for herself is not lying or cheating or distorting the truth. Through a relationship of trust, your own knowledge can grow beyond what you yourself can see.
Josef Pieper uses the example of the 17th Century naturalist studying plant leaves with a magnifying glass hearing about another’s observations with a microscope. If he has good reasons to trust the sources, then even without seeing through the microscope himself his knowledge can vastly expand. He shares in the knowledge of the one who sees. If the sources are credible (Latin, “worthy of belief”), then it is perfectly rational to believe them. In fact, this is the whole basis of our peer review system in academia.
Thus we can emphatically state that without trust, belief is impossible. If you do not trust your teacher, you will not learn a thing. “Unless you believe, you will not understand” (Is. 7:9).
Now you can object here: "But is it not better to see for oneself then to go on belief?" The Church would answer back, "Absolutely yes!" This is why the medieval project’s motto was Faith Seeking Understanding, and why St. Anselm remarked, “Insofar as possible, join faith to reason.” Surely it would be better to know everything, to see it all for ourselves, but it is simply humanly impossible. We are too limited. Human intellect is too imperfect, even in its greatness! Therefore, it is completely rational to rely on the knowledge of others. Reason demands we believe what we have heard, provided they are credible.
Now we move from the natural to the supernatural, from this natural level of belief to a supernatural level of faith.
Christianity never understood itself to be anti-rational. The early Christian Apologists (Greek for defense) wrote to Emperors and debated philosophers, making a rational defense of the Church. Historically, when Christianity spread throughout the Roman Empire they dialogued with all sorts of philosophies, but never with other religions. They saw Christianity as reasonable precisely because of Jesus, revealed in the prologue to John's Gospel with the Greek word Logos. Logos in Greek is a heavy word, it means: reason, order, structure of intelligibility, as well as idea, and word. This is where we get our suffix –logy for most of our sciences (Biology, Geology, Psychology, Theology, etc.). John uses this word logos as the name of the Second Person of the Trinity, Jesus, the reason and the word of God: “In the beginning was the Word (logos), and the Word was with God, and the Word was God. All things came to be through him" (Jn 1:1-3).
John's Gospel says that God created through his Logos, his word (thought, idea, rationality), imbuing "all things" with intelligibility. Let's take a quick pause and apply that to science. The natural sciences are possible because Nature is knowable. Intelligent creatures can know it precisely because of its logos, its rational ordering. Einstein marveled at how the universe was knowable by our human minds instead of being unintelligible. John tells us that the logos behind the created order is the Person, the Word made flesh, Jesus Christ. The Byzantine Emperor Manuel II, quoted in Pope Benedict’s famous Regensburg Address, said: “Not to act reasonably (with logos) is contrary to the nature of God.”
Natural belief concerns things of this world on level with humanity, but the object of faith is above Nature, it is supernatural, and thus its object- God and his revelation- is well above unaided human reason. How can we plumb the depths of God? Reason can point to the existence of the divine, but to know the inner life of God, to comprehend Him, is simply impossible for us. God had to reveal Himself to us. This divine self-disclosure, what we call revelation, is what the sacred science of Theology studies, applying human reason to divine revelation in a systematic way to arrive at truth. Faith and reason are thus two paths to knowing the one reality we all share.
In John 20:24-29, the story of Doubting Thomas illustrates this brilliantly. Thomas saw Jesus die. When the Apostles report Jesus rose, he refused to believe it: “Unless I see in his hands the print of the nails… I will not believe.” When Jesus stands before Thomas he says, “See my hands… do not be faithless, but believing.” Thomas then exclaims, “My Lord and my God!” Seeing the Risen Lord for himself was the rational proof of not just his resurrection, but of his claim to divinity. Thomas now sees for himself the risen Jesus and has faith that Jesus is the Son of God. Then Jesus speaks about us: “Have you believed because you have seen me? Blessed are those who have not seen and yet believe.”
Faith in Jesus Christ means trust what he says about himself as well as to entrust one’s life to Him. He is the Logos of God, the “mediator between God and man,” the “image of the invisible God” (Col 1:15). Because Jesus is the Word made flesh (Cf. Jn 1:14), he could say to his Apostles, “If you have seen me, you have seen the Father” (Jn 14:9) and John could say about him: “No one has ever seen God; the only Son, who is in the bosom of the Father, he has made him known” (Jn 1:18).
John concludes his gospel by saying, “This is the [beloved] disciple who is bearing witness to these things, and who has written these things; and we know that his testimony is true” (21:24).
Faith is not opposed to reason, but it is also not the same thing as reason. It is the ability to believe in God and what God has revealed to us. Faith expands our ability to know by sharing in the science of the saints, in their experiences, and in what they have seen. This is why St Paul says that "Faith comes by hearing" and why the old prophet tells us that "the Righteous will live by faith."