"I have not written unto you because ye know not the truth, but because ye know it." -- 1 John 2:21.
By this statement, the writer of this epistle seems to make clear that he is not addressing outsiders or even potential converts to the Christian faith. He is writing to Saints already grounded in the gospel, those who already know the truth. His purpose? "That your joy may be full."
And yet, this seems to contradict his earlier declaration, in which he states that his purpose in writing is that "ye may also have fellowship with us." At first glance, that appears to be precisely an invitation to outsiders, an appeal to join the family of the saints.
I puzzled over that tonight. Then the Spirit spoke to me. John is indeed addressing the membership, telling them: You know the truth. Now I invite you to ascend to the next level -- experience it, even as we apostles have!
To quote LDS author Robert Millet, referencing certain saints in his recollection: " Their [testimonies weren't] simply an intellectual disclosure but rather a report of personal engagement with things divine." (Holding Fast, P. 1)
We know from Jesus' words that the pure in heart are promised that they shall see God. And God keeps his promises.