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Mormonismo e Doutrina/Publicações
Question: Is everything that is published by the Church considered doctrine?
We consider the inspired words of the prophets as scripture for our time. Not everything taught in the 19th century applies to the 21st century
It is sometimes claimed that anything that is, or ever was, officially published by the Church ought to represent doctrine. We consider the inspired words of the prophets as scripture for our time. Just as Brigham Young taught principles that applied to the 19th-century saints, modern prophets teach us what we need for our particular time. Not everything taught in the 19th century applies to the 21st century.
The Church states,
Because different times present different challenges, modern-day prophets receive revelation relevant to the circumstances of their day. This follows the biblical pattern (Amos 3:7), in which God communicated messages and warnings to His people through prophets in order to secure their well-being. 
The Church manual, Gospel Principles, clarifies what is accepted as scripture,
The Church of Jesus Christ of Latter-day Saints accepts four books as scripture: the Bible, the Book of Mormon, the Doctrine and Covenants, and the Pearl of Great Price. These books are called the standard works of the Church. The inspired words of our living prophets are also accepted as scripture.