Faith is the subject of much controversy because the word has many different meanings and applications. Some phrases, like “I just didn’t have enough faith,” make faith out to be a type of wishful belief that carries power of its own. Faith often seems like something in the will and in the soul’s well of desire that mixes with some sort of spirit-magic to produce results or reveal a hidden truth.
Paul Tillich, however, has another definition of faith, one that makes a lot more sense when wondering where our “faith” has gone when we feel like it has run off. It makes sense when we wonder what stops some people from believing in God and in Christ, while others seem fully convinced of their convictions. Of faith, Tillich says this:
“Faith…is a concern of the whole person; it is the most personal concern, and that which determines all others. …it is not something which we can produce by the will to believe, but that by which we are grasped.”
Faith is something that takes hold of us, not something that we manipulate or work up. Faith isn’t like Ki energy in Dragon Ball Z, that increases by training the will and the body. It is a whole-person concern that seizes hold of the will, intellect, and emotions, and subjects them to its reality. Faith is an existential truth. For this reason, faith is a gift from God, not a work of the will (Romans 12:3; Ephesians 2:8).
In his letter to the Philippians, Paul says “I press to take hold of that for which Christ has taken hold of me” (Philippians 3:12) The entire third chapter of Philippians is a profession of faith that shows that Paul’s whole being has had an existential encounter with God’s reality, and had been grasped by it. Christ has taken hold of him, and will not let go, and for that reason is this that drives him onward and upward in his pursuit of God. It is not a feeling of guilt or compulsion, nor is it a hope or a wish for something he is unsure of. Paul is convinced.
I for one have discovered over the past few years, have discovered two things: 1) my faith has not always been something that has grabbed me, and 2) I desperately want it to be. And the more I pursue this, the more I read the Bible and the more I acknowledge to God what my faith is not, the more he begins to fortify me and bring me towards a faith that grabs me, body and soul, and shows me the truth. This doesn’t mean that I never experience doubt, but it does mean that when I do, it’s not because I never knew what I believed, like a child losing her belief in Santa Clause. It is because I can no longer see that which was presented to me to be truly real, like a cloud passing over the very real sun.
 Paul Tillich, Biblical Religion and the Search for Ultimate Reality, (Chicago, Ill: Univ. of Chicago Press, 1955), p51-52.