Hudson Taylor (missionary to China in the 19th Century) replies:
Is it not simply the recognition of the reliability or the trustworthiness of those with whom we have to do? Why do we accept with confidence a Government bond? Because we believe in the reliability of the Government. Men do not hesitate to put faith in the Government securities, because they believe in the Government that guarantees them. Why do we, without hesitation, put coins into circulation instead of as in China, getting a lump of silver weighed and its purity investigated, before we can negotiate any money transaction with it? Because the Government issues the coin we use, and we use it with confidence and without difficulty. Why do we take a railway guide and arrange for a particular journey? . . . Well, one has confidence in the reliability of these official publications. As a rule we are not put to shame!
Now, just as we use a railway guide we must use our Bible. We must depend on God’s word just as we depend on man’s word, only remembering that though man may not be able to carry out his promise, God will always fulfil what He has said... (From Hudson Taylor, A Series of Mediations)
In other words faith is not so much a faculty or some kind of sixth sense but rather a disposition of dependence towards someone or something. The application? Babies even the tiniest of infants can have faith.