"And 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."
Nephi, through the Holy Spirit is able to know the truth of the things written before he wrote and the things he, himself writes. The proof is given by the words in from of the reader as well as the testimony of the people who wrote the words and now read the words. Many times it is said in the scriptures that the words of the prophets are true. And they all testify of Christ as the Savior and the song of God.
Nephi, having recorded his revelations and findings, writes things to the best of his knowledge and skills. This gives us some of the most poignant and soul searching questions to be found in the scriptures. Pretty good for it being "according to [Nephi's] knowledge."
Nephi, himself, know Cl:list things true how? God His spirit. proof receive how? words record past, testimony people themselves write #or read. Happen many time Cl:list thing say prophet their words true. words all same say, Christ Himself God His son, also Savior world.
Nephi himself record Cl:list things revelation understand. Satisfy talent. Many question++ have. Some sad ponder+++. Whew good question from Nephi himself.