Summary: In my previous post (Are Mormons Brainwashed?) I pointed out that Mormonism is not driven by systematic theology. I use the term in a very narrow sense. I take it to mean a precisely defined, unified system usually involving philosophical methods and authoritative sources like scripture. Consequently, if one element is changed, or expressed differently, then the other elements must be altered to maintain consistency. The theologian’s job is to iron out the inconsistencies that arise.
This level of precision is behind most religious schisms. At some point someone interpreted the bible differently and concluded the existing tradition was flawed. To a Mormon many of the differences seem trivial, but to those involved, the very truth, and ultimately salvation, is at stake. So they form a new church claiming it is more correct.
Mormonism did not come about through doctrinal schism. Our tradition goes back to the First Vision (The First Vision); our doctrines are based on revelations given to the prophets. And we accept this. There are no professional theologians in the Mormon tradition who work out inconsistencies, define terms, and make the belief system uniform. The famous book by Bruce R. McConkie is title Mormon Doctrine, not Mormon Theology.
From time to time I have found the lack of formalism a little frustrating. And this is one of the reasons I blog: to express my beliefs in a tighter way (Why I Blog). But I make an effort to keep it consistent with the tradition I was raised in. A tradition of teachings and scripture that I have a testimony of, that they are true. I do not claim my writings are ultimately correct. And I try to avoid being too precise, which I believe would be an error. I only hope they are useful to others as they are to me. And I’m very OK with people disagreeing with them.
We all have many false beliefs and I believe God is very tolerant of this. We are ultimately judged by what we did, and did not, do. Not by what we correctly, or incorrectly, believed.
But given that Mormon beliefs are not driven by systematics then how are our beliefs established? If there are no theologians expressing doctrine then what drives acceptance of Mormon religious teachings?
So how are Mormon beliefs established? Mainly they are driven by tradition and scripture. New revelations added to the scriptures are rare. But interpretation of scripture is based heavily on tradition. This post will focus primarily on tradition.
Context is Everything
There are various ways in which statements from the Apostles and Prophets are expressed, and depending on the context a different level of importance will be attached. For example, something the Church President says to a reporter is not taken to be as important as something said in General Conference.
Depending on the context in which a prophet speaks a Mormon will apply different types of confidence to what they say. These are not defined, described, or formalized in any way. But they are part of how we think.
If a Church President, Apostle, or any other General Authority makes a statement, a Mormon might ask herself any of the following questions.
Did it contain the words “thus saith the Lord”? Was it a vision? Was it endorsed by the First Presidency, the Twelve Apostles, and all other General Authorities? Was it said in General Conference? Was it sustained by the Church? Was it repeated many times? Was it in a speech to college students, at a seminary conference, or some other kind of gathering? Was it intended to be binding forever, or intended for present circumstances? If it is something written in a book, was it written before he became a General Authority, Apostle, or Church President? Was it published by The Church of Jesus Christ of Latter-day Saints, or Deseret Book, or some other publishing company? If it is something from a past prophet, was it declared publicly or, for example, written in his diary? Was it a statement to be read by the bishops to their congregations? Was it published on the church’s website or in the Ensign magazine? Was it something said in an interview? Was the interviewer a member of the Church’s Public Affairs staff? Was it a statement that came from the Office of the First Presidency, or released by the Public Affairs Office?
No matter how the prophet says something it will be taken seriously. Some take his utterances to be doctrine regardless of context. But Joseph Smith said, “a prophet [is] a prophet only when he was acting as such.” Consequently a prophet is not infallible, which is why the support of the General Authorities is so important.
A statement by the President of the church to a reporter is not binding for the church, though it is still taken seriously.
For example, during a 60 Minutes interview Mike Wallace asked President Hinckley, “No alcohol, no tobacco, no coffee, no tea, not even caffeinated soft drinks…?” President Hinckley responded, “Right.” (See transcript here; see The Word of Wisdom) Many Mormons (and non-Mormons) take this as confirmation that the church bans caffeinated soft drinks. But precision cannot be expected in an interview where several questions get asked together. However, if he had said the same thing in General Conference members would attach a much higher significance to it.
Statements of the First Presidency (not submitted for sustaining)
Often the First Presidency will make Official Statements. These are usually policy statements, clarification on doctrine, or statements on important issues. They are considered inspired and taken very seriously. But circumstances change. What was important 100 years ago might not be important today, so statements can become dated. Consequently, what the living prophet says is weighted more heavily than statements from past prophets.
Revelations of the Prophet Sustained by the Church
A revelation received by the prophet can be brought before the church and sustained. An example of this process is described in Official Declaration 2, regarding ordination of black men to the priesthood.
[President Kimball] presented it to his counselors, who accepted it and approved it. It was then presented to the Quorum of the Twelve Apostles, who unanimously approved it, and was subsequently presented to all other General Authorities, who likewise approved it unanimously.
Lastly it was presented to the Church for acceptance,
Recognizing Spencer W. Kimball as the prophet, seer, and revelator, and president of The Church of Jesus Christ of Latter-day Saints, it is proposed that we as a constituent assembly accept this revelation as the word and will of the Lord. All in favor please signify by raising your right hand. Any opposed by the same sign (Official Declaration 2).
This process makes a revelation officially binding for church members. Official Declaration 2 was eventually included in our scriptures.
Statements in published books are another level. Something published in a book is not as binding as the same thing said in General Conference. Though, it would be taken seriously.
As far as print goes there are three levels. They are, in descending order of importance: things published by the Church of Jesus Christ of Latter-day Saints; things published by Deseret Book (a publishing company owned by the Church); and things published by another publisher.
Another level of context should be added: Was he a Seventy, Apostle, or Church President when it was published? For example,
During David O McKay’s tenure as president of the church, Joseph Fielding Smith, who was president of the Quorum of Twelve Apostles and next in line to become President of the church, published a book called Man His Origin and Destiny, which contains a strong anti-evolution stance. In it President Smith wrote, “This brings us to the discussion of what I believe to be the most pernicious doctrine ever entering the mind of man: the theory that man evolved from the lower from of life” (p. 133). Apostle Mark E. Peterson wrote the foreword and mentions that he and others encouraged Smith to write the book. Since it received support from other Apostles, and was published by Deseret Book, it carries a sense of authorization. During a meeting with members of the staff of the Institute of Religion at the University of Utah President David O. McKay said, “that book should be treated as merely the views of one man…It is true that [this] one man is President of the Twelve, and [that] makes it more or less authoritative, but it is no more to be taken as the word of the Church than any other unauthorized book” (David O. McKay and the Rise of Modern Mormonism, p. 47).
For another example see footnote .
Frequently and by Many
Repetition is yet another type of confidence, and a very important one. Greater confidence is placed in doctrinal statements that get repeated over time.
If a prophet says something very different from current accepted beliefs, and it is not repeated by him or anyone else, there would be little sense of obligation toward it. This is especially true if what was said is unusual.
For example, on April 9, 1852 Brigham Young said, “[Adam] is our Father and our God, and the only God with whom we have to do” (Journal of Discourses, vol. 1, pp. 50-51). That is a very unusual statement and at face value is not consistent with Mormon teachings. I have never encountered this idea from contemporary church leaders; neither have I seen it in any material published by the church. I don’t feel any obligation toward it. The church does not consider the Journal of Discourses to be authoritative. 
Apostle Neil Anderson said in 2012 October General Conference,
There is an important principle that governs the doctrine of the Church. The doctrine is taught by all 15 members of the First Presidency and Quorum of the Twelve. It is not hidden in an obscure paragraph of one talk. True principles are taught frequently and by many…
(“Trial of your Faith,” General Conference Talks, LDS.org, October 2012)
 History of The Church of Jesus Christ of Latter-day Saints, 7 volumes, edited by Brigham H. Roberts, (Salt Lake City: Deseret Book, 1957), 5:265,<https://byustudies.byu.edu/hc/hcpgs/hc.aspx?HC=/hc/5/1.html&A=265> accessed 12/06/2014.
 The “60 Minutes” program on the LDS Church, Broadcast on CBS TV, April 7, 1996 <http://www.lds-mormon.com/60min.shtml> accessed 12/06/2014.
 In 1958 a book called Mormon Doctrine, written by Bruce R. McConkie then a Seventy, was published. In this book McConkie stated that “The Roman Catholic Church specifically–singled out, set apart, described, and designated as being ‘most abominable above all other churches’” (p. 129, italics original). The First Presidency learned of the book only after it was published. They asked Elder McConkie to remove that reference and change several other things that were questionable. McConkie complied and the changes were made. Consequently that passage is found only in the first edition.
Mormon Doctrine is not published by the Church or by Deseret Book. Bruce R. McConkie eventually became an Apostle.
The preface to Mormon Doctrine reads, “For the work itself, I assume sole and full responsibility. Observant students, however, will note that the standard works of the Church are the chief sources of authority quoted and that literally tens of thousands of scriptural quotations and citations are woven into the test material.” (Note: Mormon Doctrine really is a very good source of information for Mormon beliefs.)
 “The Journal of Discourses is not an official publication of The Church of Jesus Christ of Latter-day Saints. It is a compilation of sermons and other materials from the early years of the Church, which were transcribed and then published. It included some doctrinal instruction but also practical teaching, some of which is speculative in nature and some of which is only of historical interest.” (Gospel Topics, “Journal of Discourses”)
McConkie, Bruce R. Mormon Doctrine. Salt Lake City: Bookcraft, 1958.
Prince, Gregory A., and Wright, Robert Wm. David O. McKay and the Rise of Modern Mormonism. Salt Lake City: University of Utah Press, 2005.
Smith, Joseph Fielding Smith. Man His Origin and Destiny. Salt Lake City: Deseret Book Company, 1954.