Having been asked to explain our beliefs on another site, I was called upon to talk of our opinion of the Bible. However as that isn't the only source of truth we have I had to extend the discussion to explain what we regard as sources of truth.
The Baptist minister had trouble with what he termed "changing doctrine" of the church. So I thought it best to explain just how, as an LDS, I determine which doctrines, of those I'm presented with, to recognise as the fullest truths. As the subject is so important I thought I'd share this information as a post on this site.
When my children were really little I told them never to touch a power socket/point/jack or power cords. As my oldest got on she was somewhat shocked to have me one day tell her to plug in a power cord. And as time went on I eventually taught her to take one apart and repair it. If, on the other hand, one of my children wasn't responsible with this freedom I would remove the right from them, and give them back the more basic law, until I felt I could give them another go. So is our Heavenly Father with us.
Two examples of this in the Bible are, first the giving of the law of Moses to Israel when previously the gospel of Jesus Christ was known (Heb 3:16 & 4:2), and second the re-establishment of the gospel of Jesus Christ at the time of John the Baptist (Lk 16:16).
While these situations may be considered by some to be "changing doctrine" nothing had really altered. It never was good to be angry with anyone, or to lust anyone etc. So Christ wasn't creating NEW concepts, but improving the information level.
Therefore as levels of knowledge, within the church generally, can rise and fall (e.g. read D&C 119 heading), the question arises as to how I determine what is the greater truth, as a sincerely searching LDS wishing to progress beyond the basic level?
There are many readable sources I can find information for consideration from. The first and primary readable source is the Standard Works (scriptures). Conference talks and books by past church leaders are good for ideas also.
But, in the end, these do pose some problems in being certain of the fullness of every statement contained therein. For example the prophets prior to Christ in the Book of Mormon and Old Testament could only speak from personal knowledge. And in spite of some inspiration their knowledge wasn't as full as ours should be: They didn't have the sermon on the mount to refer to etc. Their thinking reflected the law of Moses that they were under. So statements they made about God weren't made with as much additional knowledge in many cases.
Next, as the people they were speaking to were often even less informed, the level of information was a bit on the down side for this reason also. This same situation exists to some degree in the church today, as there are new members and those not really ready for deeper understanding, to consider. It is important to give people milk before meat (as Christ and Paul pointed out). So even those things stated by GAs today become limited, as a member stretches on in learning past those basics.
This leads next to the importance of prayer and revelation from the Holy Ghost. In addition to the Holy Ghost you can have personal, two-way, discussion with Heavenly Father or with Jesus Christ, as have had many before us. However even here some will protest that information can come from the wrong source and we may be being deceived. So how can we really know?
Quite simple. Several ways exist of knowing truth from error. These skills can be obtained by practice and looking into yourself. So even though some mistakes may initially be made you will soon get the hang of it. Just allow for the teething problems; keep yourself focused on Heavenly Father and Jesus Christ and you will be fine.
Firstly there is feeling from the messenger (if inspired - which truth generally will be). The dark side (Satan and his mates) are exactly that. And their ways are obvious - anger, hate, revenge, despair, greed, etc. On the other hand God gives freedom, has love, peace, forgiveness, patience and all those other good things.
Next, there is light in truth. If the thing is completely true it will cause light in you that your spirit will love (this light is actually visible to your spirit eyes). If it is only partially right it won't be exactly like that, but will still have some feeling of good. I then know it needs further work, but I'm on the right track. If it is completely wrong I won't feel this at all, and the Holy Ghost may inform me that I'm up the wrong track altogether.
Naturally it shouldn't oppose the highest of Scriptural messages (the sermon on the mount). This was delivered by Christ himself to an audience that had the spiritual interest to actually go out and listen. So that is the peak of his doctrine.
Then there is the fact that it fits in this place in eternity. If it can't fit in a spot in eternity then it is false. Search sincerely for that and you will find it.
It has to fit with reality. If real life seems to oppose the idea then either your perspective of real life needs examining or it is false.
Living principles have the obvious living test. That is that if you practice them fully for a sustained period and nurture them, they will make you feel good inside. Some principles require little testing, and some require extended effort, to prove. A simple test of living principles is to go to a hospital and visit a person not getting visitors. Put that person's face in your head afterward and think of how pleased they were you came. Then ask yourself if you can't feel a good feeling in your heart?