The apostles ask for more faith. Jesus does not respond yes or no, but in a parable. If you have faith like a grain of mustard seed, you could say to this mulberry tree, ‘be uprooted and planted in the sea’, and it would obey you (Luke 17).

More is not the point. A little faith is enough for impossible things.

In my study of this passage I discovered there were 4 different words for faith used in the gospels. Assensus is the type that is predicated on belief in a truth. It is you accenting to an idea or a person. This is the type that the Western person usually think of and consequently stops at. On its own, it is not enough to transform your life from idolatry and anxiety. The other 3 are more relational. There is fiducia (trust), (fidelitas) fidelity, visio – the way you precieve the world and the events that happen to you. The married woman ideally has trust in her husband and does not doubt every decision he makes. And ideally, both are faithful to each other through not cheating on one another. Lastly, in a healthy marriage, they assume the best in one another.

Head knowledge alone is not enough to change your heart if the others are ignored. “Christ is the good shepherd and came so we may have life, and have it abundantly”

Reference

Luke 17
Youtube video on 4 types of faith.