We live in a world where "seeing is believing." However, when Christ prodded his apostles with the question, "Whom say ye that I am," Peter replies, "Thou art the Christ, the Son of the living God." To which Jesus replies, "Blessed art thou...for flesh and blood hath not revealed it unto thee, but my Father which is in heaven."(Matt 16:15-17) Alma, the son of Alma in the Book of Mormon, had seen an angel and was struck dumb and paralyzed for days because of his adamant rebellion. When explaining his conversion and acceptance of Christ to the people in Zarahemla, he doesn't even mention this encounter:
"They are made known unto me by the Holy Spirit of God [Holy Ghost]. Behold I have fasted and prayed many days that I might know these things of myself. And now I do know of myself that they are true; for the Lord God hath made them manifest unto me by his Holy Spirit; and this is the spirit of revelation which is in me." (Alma 5:46)
Regarding this "spirit of revelation," Christ continued his praise of Peter thus, "Upon this rock I will build my church; and the gates of hell shall not prevail against it." From Christ's time, before and after, his church was meant to be established on the rock of revelation. For a church to be his church, he is to be the head. And how can Christ be the leader if revelation isn't guiding the "authorities" of the church? How can one claim to be a church of Christ except they also seek for and acknowledge guidance from him?
To Joseph Smith also came the priesthood authority held by the prophets of old, that men still hold today. Through this Melchizedek Priesthood, worthy, baptized members of the Church of Jesus Christ of Latter-Day Saints receive the gift of the Holy Ghost which testifies of God and Jesus Christ to our hearts. It teaches us through revelation, and the best way to retain that revelation is to write it down! Study journals have facilitated personal revelation for me, and they have uplifted me on more than one occasion as I go back and read exerts I have written sometimes years before.
I know that Jesus Christ is my savior, that Joseph Smith was called by God to be a prophet and that the Book of Mormon and Bible are God's words to those people as well as to us and our children. As did Alma, I know all these things through, "the spirit of revelation which is in me."