"Were this class [YOU] to go back and reflect upon the history of their lives, from the period of their first recollection, and ask themselves, what principle excited them to action, or what gave them energy and activity, in all their lawful avocations, callings and pursuits, what would be the answer? Would it not be that it was the assurance which we had of the existence of things which we had not seen, as yet?—Was it not the hope which you had, in consequence of your belief in the existence of unseen things, which stimulated you to action and exertion, in order to obtain them? Are you not dependent on your faith, or belief, for the acquisition of all knowledge, wisdom and intelligence? Would you exert yourselves to obtain wisdom and intelligence, unless you did believe that you could obtain them? Would you have ever sown if you had not believed that you would reap? Would you have ever planted if you had not believed that you would gather? Would you have ever asked unless you had believed that you would receive? Would you have ever sought unless you had believed that you would have found? Or would you have ever knocked unless you had believed that it would have been opened unto you? In a word, is there any thing that you would have done, either physical or mental, if you had not previously believed? Are not all your exertions, of every kind, dependent on your faith? Or may we not ask, what have you, or what do you possess, which you have not obtained by reason of your faith? Your food, your raiment, your lodgings, are they not all by reason of your faith? Reflect, and ask yourselves, if these things are not so. Turn your thoughts on your own minds, and see if faith is not the moving cause of all action in yourselves; and if the moving cause in you, is it not in all other intelligent beings?"
"it [faith] is the principle by which Jehovah works, and through which he exercises power over all temporal, as well as eternal things..."
The Savior says, (Matthew 17:19-20), in explaining the reason why the disciples could not cast out the devil, that it was because of their unbelief: "For verily, I say unto you," said he, "if ye have faith as a grain of mustard-seed, ye shall say unto this mountain, Remove hence to yonder place! and it shall remove: and nothing shall be impossible unto you."
DOES A MUSTARD SEED DOUBT WHAT IT CAN BECOME?