Faith unto knowledge--giving the holder of such faith the power to act without confirmation that the event has taken place--means to understand something so much that its process is given always with an expected outcome.
If God speaks to a mountain with instructions to move, it will do so, and He knows it! That is faith unto knowledge!
God gave this power to a prophet named Nephi, a great missionary among the Nephites. Mormon records the words of the Lord to Nephi as such:
...thou art Nephi, and I am God. Behold, I declare it unto thee in the presence of mine angels, that ye shall have power over this people, and shall smite the earth with famine, and with pestilence, and destruction, according to the wickedness of this people.Just as God knows all things and has all power, Nephi knew that he possessed the power of God and exercised that power as recorded in The Book of Helaman.
Behold, I give unto you power, that whatsoever ye shall seal on earth shall be sealed in heaven; and whatsoever ye shall loose on earth shall be loosed in heaven; and thus shall ye have power among this people...(Helaman 10:6-7)
Just as Nephi exercised that power, God can give it to us to have that same faith unto knowledge. We can know that God lives, even though we have not seen Him. We can know that we are His Children.
How? We can know by the power of the Holy Ghost, who is the testifier member of the Godhead, or the three that make us the Godhead: God the Father, Jesus Christ and the Holy Ghost.
We can have so much faith in God and His power that it evolves into knowledge!
Just as we know when we switch on a light switch light will come, we can know when we pray that god will answer.
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Faith Unto Knowledge