I'm confused by Revelation 22:18–19, which tells us not to add anything to the word of God.

One of our key beliefs is that God has always revealed His will to His children on earth and always will. We believe the Bible to be the word of God but don't believe it contains all the revelation that God has given or will give His prophets. Even today He continues to reveal His will through living prophets and apostles, the foundation of The Church of Jesus Christ of Latter-day Saints (see Ephesians 2:20).

When the Apostle John penned the book of Revelation, it was not the last book of the Bible. The Old and New Testaments were not bound in a single book of scripture—now called the Bible—until the third century A.D.

In the same way, Deuteronomy 4:2 tells us not to add to the words of Moses. Of course, this verse, early in the Old Testament, does not invalidate the rest of the Bible. Neither Moses nor John could have referred to altering a volume that did not exist yet; instead they warned against altering the true teachings of the gospel.

The Book of Mormon, which contains the fulness of the gospel, does not alter God's word but reaffirms it. (For more on this topic, see 38 in this issue.)