Faith is a measure of the totality of our experience. Perhaps you would say to me that faith is blind, meaning that faith requires us to believe in something that has no basis in fact. Something that we must believe even though all our senses and intelligence tell us that it cannot be true. Blind faith means we should believe something when we have no experience that would suggest that it has possibilities. Believing in something we cannot possibly expect to happen would seemingly be impossible, or at the very least it would seem to be very unlikely.

Faith is the expectation that an event is likely to occur. This expectation is based on experiences that show us this likelihood exists. For example, if you are a carpenter and I ask you if you can build a room for me, you would answer yes. This yes would be based upon your past experience, i.e. You have built many rooms before, you have been well trained in the subject, and there would be no reason for you to think that you could not achieve the same goal again. So it would be fair to say that you have faith in your ability to build this room. On the other hand, if I asked you if you could change a rainy day into a sunny day, what would your answer be? First, you would know what Christ said about a grain of mustard, but you probably have had little or no experiences with changing the weather. Chances are you would say no, or in your heart you would be very doubtful. It would be fair to say that you did not have faith in your ability to change the weather. If, on the other hand, you had seen the weather changed before, things might be different. From your experience, you would know it is possible. If you believed in your heart you could achieve that goal, you could. That is the faith of a grain of mustard that Christ speaks of.