I know that the record which I make is true; and I make it with mine own hand; and I make it according to my knowledge.He makes a similar declaration in 1 Nephi 14:30. This has the feel of a legal declaration, a representation or warranty. Or perhaps he is just affirming the truth of the record like we might affirm the truth of a story we are relating in everyday conversation. In that sense, the affirmation serves to clarify that we are trying to describe facts rather than spinning a tale. In either event, the value of Nephi's declaration is that he was an eyewitness to most of the events described in the record. For those who knew Nephi -- or did not doubt his existence -- this would have been a valuable piece of evidence for the truth of the record.
To the modern reader, however, Nephi's declaration has less value. The problem is that Nephi could be a fictional person, in which case the declaration would be worthless. It's just the sort of thing a fictional person would be made to say when the author is attempting to provide credibility to a specious record.
The challenge, then, is evident: how can we know that the record is true when we have no credible evidence beyond the record itself? Elsewhere (2 Nephi 25:20) Nephi bears testimony of a record that he did not make. King Benjamin does the same thing. Mosiah 1:6. So does Alma. Alma 3:12. Of course, in each of these instances, the witness had no reason to doubt the existence of the people who created the record of which they are testifying.
So the question remains on the table: how do we know whether the Book of Mormon is a true record?
In Mosiah 1:6, King Benjamin makes a fascinating declaration in reference to the plates of Nephi: "they are true, and we can know of their surety because we have them before our eyes." Two thousand years later, those same records were shown to eight witnesses, but those witnesses said nothing about the truth or falsity of the record. Instead, they merely affirmed the existence of the records:
Joseph Smith, Jun., the translator of this work, has shown unto us the plates of which hath been spoken, which have the appearance of gold; and as many of the leaves as the said Smith has translated we did handle with our hands; and we also saw the engravings thereon, all of which has the appearance of ancient work, and of curious workmanship. And this we bear record with words of soberness, that the said Smith has shown unto us, for we have seen and hefted, and know of a surety that the said Smith has got the plates of which we have spoken.Notice the distinction between King Benjamin's declaration and the testimony of the eight witnesses. While King Benjamin testified that the records were true, the eight witnesses merely testified that Joseph had the plates. Something more was needed to provide a witness of the truth. We find that something in the Testimony of the Three Witnesses:
We, through the grace of God the Father, and our Lord Jesus Christ, have seen the plates which contain this record, which is a record of the people of Nephi, and also of the Lamanites, their brethren, and also of the people of Jared, who came from the tower of which hath been spoken. And we also know that they have been translated by the gift and power of God, for his voice hath declared it unto us; wherefore we know of a surety that the work is true. And we also testify that we have seen the engravings which are upon the plates; and they have been shown unto us by the power of God, and not of man. And we declare with words of soberness, that an angel of God came down from heaven, and he brought and laid before our eyes, that we beheld and saw the plates, and the engravings thereon; and we know that it is by the grace of God the Father, and our Lord Jesus Christ, that we beheld and bear record that these things are true.Seeing the records was not enough. They obtained their witness "by the gift and power of God," just as foretold in Ether 5:3: "And unto three shall they be shown by the power of God; wherefore they shall know of a surety that these things are true."
This observation is entirely consistent with the instruction typically given by missionaries to read and follow Moroni 10:3-5, where the Prophet Moroni admonishes readers of the record to "ponder it in your hearts" and "ask God, the Eternal Father, in the name of Christ, if these things are not true." If you do that "with a sincere heart, with real intent, having faith in Christ," Moroni claims, "he will manifest the truth of it unto you, by the power of the Holy Ghost." Indeed, by this power "ye may know the truth of all things."