What is faith?

Faith does not mean that God exists or does not exist, that there is certainty that He exists or does not exist, not even mathematical certainty. Faith means that when you believe in God, and compose for God like Bach or build for God like Brunelleschi, you give your all, because you are not serving men who are imperfect and who can deceive you, you are serving God, an omnipresent being, and only by creating for perfection can you achieve perfection.

That is why it is said that faith moves mountains.