Faith is a difficult thing to articulate. But it is central to every theological discussion. I would add that it is vital to every scientific discussion, too, at least for those who profess to believe in God and carry on scientific discussions. It's not that science and faith are opposites. Science is not an inherent threat to faith. On the contrary, science can be the "evidence of things not seen."
For example, I marvel at the heavens. Often, I wonder which star is my Heavenly Father's abode. Recently, I found a picture on the internet taken by the Hubble telescope. The astronomers who took it focused on a dark part of the night sky which from the ground is the size of a dime. They found thousands of galaxies, each with its millions upon millions of stars. On that webpage, I saw "God moving in His majesty and power." Yes, such a scene is evidence that God lives. And considering the millions upon millions of stars hidden in one dime-sized circle in the night sky, how many stars do God's heavens veil?
Yet it is not God's desire to veil his purposes from us. We do that well enough ourselves. God's purpose is not the creation of galaxies and stars; it is the perfection of his children. You see, He forms the stars for the same reason He created the Earth: "This is my work and my glory," He said, "to bring to pass [our] immortality and eternal life." That is the impetus of all His works. And that is a statement of His purposes in the broadest sense.
Although God's children are legion, his purposes extend to us individually, not in some trickle-down sort of way but as a straight and strong rod directly from his throne. I've felt such purpose in my life as I've listened to the whisperings that come in quiet times. I suppose faith is trusting in those whisperings.
But faith in God's purposes may wane when it seems his promises remain unfulfilled. So why do promises fail? The answer is simple, "I the Lord am bound when ye do what I say, but when ye do not what I say, ye have no promise." God's promises are always conditioned on our obedience.
But there is more depth to God's unfulfilled promises. When Oliver Cowdery first came to Joseph Smith to assist in the translation of the Book of Mormon, the Lord revealed that Oliver would also have the gift of translation, if Oliver so desired. Now, God knew that Oliver would fail, but the promise extended to Oliver.
We may think God is cruel to promise what He knows will not come to pass. But His purposes are deeper. Oliver did try to translate. He commenced well, but because he did not continue as he commenced, he failed. And I believe it was only in Oliver's failure that he, and we through him, could learn the lesson that the Lord wished to teach him.
The Lord's rebuke to Oliver is the single-most stunning description of the process of revelation: "Study it out in your mind and in your heart, and then ask me if it is true, and if it is true, I will cause your bosom to burn within you. But if it is not true, you shall have no such feelings."
I learn best after I have struggled and failed. It's not that failure makes me more susceptible to teaching; rather failure is humbling. God actually told Oliver how to translate, "I will tell you in your mind and your heart." But Oliver failed to learn. Most likely, Oliver was sure of himself; if a country bumpkin like Joseph could translate, how hard would it be for an educated man? It was not until after Oliver was humbled that the Lord could truly teach him. But great was the price of Oliver's failure. Will we fail to learn from his experience?
The process of revelation that the Lord tried to teach Oliver is the essence of faith. So often, we go to the Lord with a question, and so often, we take no thought but to ask Him. Elder David Bednar of the Quorum of the Twelve Apostles compared this process to having a pillar of light surrounding us. Everything else is black. We don't know if we are to turn around, to step right or left, or to move forward, so we go to the Lord and say, "Lord, move the light, and I will follow."
To this the Lord says, "Study it out in your mind and in your heart; decide first which way to go, and I will tell you if you are going in the right direction." So we listen to Him and study it out. Then we ask again. "Lord," we say, "I'm going to step forward; please move the light." Instead of moving the light, He may send a stupor of thought to dissuade us, or He may send peace and say, "Take a step, and the light will move." He has revealed His will to us, but we must still trust.
This is faith: knowing God's will, and moving forward even though we cannot see the future consequences of our actions.
Then, as we look back on the path we have taken, we will see the ever present guidance of Deity.