In a used book store in DC a couple of weeks ago, I found a very cheap book in the philosophy section by Spanish writer Miguel de Unamuno called Tragic Sense of Life. Unamuno wrote at the beginning of the 20th century during the time when his country fell under the tragic dictatorship of Franco. He was a devout Catholic who watched in horror as the Catholicism around him was perverted into fascism. The description on the back cover that attracted me said that Unamuno “makes a strong plea for passion over rationality, heart over head, faith over reason.” I’m always up for a little romanticism. A good bit of the book seems like poetic esoteric nonsense, but several passages about the nature of faith seemed worth sharing.
Throughout the book, Unamuno contrasts believing in the idea of God with actually believing in God. In this passage, he describes what he thinks it means for us to believe in God.
Wishing that God may exist, and acting and feeling as if He did exist. And desiring God’s existence and acting in conformity with this desire, is the means whereby we create God–that is, whereby God creates Himself in us, manifests Himself to us, opens and reveals Himself to us. For God goes out to meet him who seeks Him with love and by love, and hides Himself from him who searches for Him with the cold and loveless reason… Knowledge without love leads us away from God; and love, even without knowledge, and perhaps better without it, leads to God, and through God to wisdom. 
What I really appreciated about this is the way that it concedes that faith is living “as if.” From our vantage point, it may even feel like we are “creating” God by living as if God exists. We cannot discover God’s presence in the world without longing for it. As long as we are engaging the question of God’s existence as a logical problem, we will not find Him.
Rationalists seek definition and believe in the concept, while vitalists seek inspiration and believe in the person. The former scrutinize the Universe in order that they wrest its secrets from it; the latter pray to the Consciousness of the Universe, strive to place themselves in immediate relationship with the Soul of the World, with God, in order that they may find the guarantee or substance of what they hope for, which is not to die, and the evidence of what they do not see. 
This passage describes two different postures we can take towards truth. We either seek to conquer truth or we seek to be inspired by it. Even among Christians, you can find these two different postures. Some of us want to conquer God’s truth so that it can serve us. Others want to be moved by God’s truth so that we can serve God. At the end of the passage, Unamuno is riffing on Hebrews 11:1’s definition of faith as “the substance of things hoped for, the evidence of things not seen.” He understands our seeking God in terms of our longing for immortality. Unamuno continues to riff on the relationship between faith and hope in this next passage.
Faith is our longing for the eternal, for God; and hope is God’s longing, the longing of the eternal, of the divine us, which advances to meet our faith and uplifts us. Man aspires to God by faith and cries to Him: “I believe–give me, Lord, wherein to believe!” And God, the divinity in man, sends him hope in another life in order that he may believe in it. Hope is the reward of faith. Only he who believes truly hopes; and only he who truly hopes believes. 
Faith, in a certain sense, creates its object. And faith in god consists in creating God; and since it is God who gives us faith in Himself, it is God who is continually creating Himself in us… The power of creating God in our own image and likeness, of personalizing the Universe, simply means that we carry God within us… and that God is continually creating us in His own image and likeness. And we create God–that is to say, God creates Himself in us–by compassion, by love. To believe in God is to love Him, and in our love to fear Him; and we begin by loving Him even before knowing Him, and by loving Him we come at last to see and discover Him in all things. [192-193]
It might make some Christians wince a little bit to see somebody write that our faith “creates” God even though Unamuno always qualifies this by saying actually God creates Himself in us through our faith. But I’m hoping that this way of talking might be helpful to people who aren’t sure they believe in God because they’re waiting for some proof of God to compel their belief in Him. That never happens. God’s presence appears to us as a product of our living as if He is real, a product of our love for Him and need for Him.
Those who say they believe in God and yet neither love nor fear Him, do not in fact believe in Him but in those who have taught them that God exists… Those who believe that they believe in God, but without any passion in their heart, without anguish of mind, without uncertainty, without doubt, without an element of despair even in their consolation, believe only in the God-Idea, not in God Himself. 
I definitely agree with this passage. If you lack doubt and anguish in your relationship with God, it probably means you don’t have any skin in the game and what you call “God” is really just the God-Idea, a concept that is useful to you rather than a person who creates turmoil in your heart. Of course the reality is that most of us who like to think about theology have a sort of hybrid belief in both God and the God-Idea. But it is easy to get so preoccupied and invested in my concepts about God that I am aloof to the person of God Himself.