Doctrine - what is it and can it change?

What is Doctrine? 
Doctrines are principles and concepts that form "Truth" - eternal truths needed for the salvation of men.  Complete fully understood doctrine is "Truth" and will not and cannot change.  However none of us in any sense of the word knows the complete "truth" as will be discussed below.... thus our understanding of Doctrine can and does change!

D&C 93:24
24 And truth is knowledge of things as they are, and as they were, and as they are to come;

What is the Doctrine if Jesus Christ?
Here are some great references concerning this topic
The Doctrine of Christ - Ensign April 2012 Todd Christofferson
The Living Prophet: Our Source of Pure Doctrine - Ensign October 1998 Merrill C. Oaks
Stand forever - Lawrencx E. Corbridge BYU Speaches


The Doctrine of Christ - Ensign April 2012 Todd Christofferson
"3 Nephi 11:32–35, 39

“This is my doctrine, and it is the doctrine which the Father hath given unto me; and I bear record of the Father, and the Father beareth record of me, and the Holy Ghost beareth record of the Father and me; and I bear record that the Father commandeth all men, everywhere, to repent and believe in me.
And whoso believeth in me, and is baptized, the same shall be saved; and they are they who shall inherit the kingdom of God.
And whoso believeth not in me, and is not baptized, shall be damned.
… And whoso believeth in me believeth in the Father also; and unto him will the Father bear record of me, for he will visit him with fire and with the Holy Ghost. …
Verily, verily, I say unto you, that this is my doctrine, and whoso buildeth upon this buildeth upon my rock, and the gates of hell shall not prevail against them.

This is our message, the rock upon which we build, the foundation of everything else in the Church. Like all that comes from God, this doctrine is pure, it is clear, it is easy to understand—even for a child. With glad hearts, we invite all to receive it."

"We value scholarship that enhances understanding, but in the Church today, just as anciently, establishing the doctrine of Christ or correcting doctrinal deviations is a matter of divine revelation to those the Lord endows with apostolic authority."

Can Doctrine change?

Article of Faith #9
9 We believe all that God has revealed, all that He does now reveal, and we believe that He will yet reveal many great and important things pertaining to the Kingdom of God.

The principle of continuing revelation is an essential part of the kingdom of God and has always been so.  During each and every dispensation of the Gospel the revealed word of God has updated/clarified and provided the proper interpretation of the word of God to the people of the time.  Thus providing them the Word of God to them, for their situation and time.  

D&C 21
4 Wherefore, meaning the church, thou shalt give heed unto all his words and commandments which he shall give unto you as he receiveth them, walking in all holiness before me;

5 For his word ye shall receive, as if from mine own mouth, in all patience and faith.

6 For by doing these things the gates of hell shall not prevail against you; yea, and the Lord God will disperse the powers of darkness from before you, and cause the heavens to shake for your good, and his name’s glory.

Does the lord provide doctrine to his children in it's complete form?
In every case the answer is NO.  
I'll say it again in every case the answer is NO, there is always and will always be a clarification, and perfection of the principles of the Gospel over time until we all come to a perfect knowledge and comprehend all things.
Do we have a perfect understanding of the doctrines of the kingdom today?  NO - for we believe that there are yet many great and marvelous things that will be revealed to the world and the Church.

The Doctrine of Christ - Ensign April 2012 Todd Christofferson
"As the policies and procedures of the Church are refined by continuing revelation and inspiration, there are those who become disturbed by any changes. Some literally hunt for situations where earlier Church leaders or members made statements which are not in complete harmony with our understanding and practices today. The mind-set of some is that anything coming from an earlier time must be more correct."

2 Nephi 28:30
30 For behold, thus saith the Lord God: I will give unto the children of men line upon line, precept upon precept, here a little and there a little; and blessed are those who hearken unto my precepts, and lend an ear unto my counsel, for they shall learn wisdom; for unto him that receiveth I will give more; and from them that shall say, We have enough, from them shall be taken away even that which they have.

The means by which the Lord provides his doctrine and principles of his kingdom to the world, and the church is based upon this principle.  The church is a living church - powered by the Holy Ghost and the revelations to the members as well as to the President and Prophet by which new revelation is provided to the church that they may grow to a perfection of the knowledge of God.

D&C 93:30-32

30 All truth is independent in that sphere in which God has placed it, to act for itself, as all intelligence also; otherwise there is no existence.

31 Behold, here is the agency of man, and here is the condemnation of man; because that which was from the beginning is plainly manifest unto them, and they receive not the light.

32 And every man whose spirit receiveth not the light is under condemnation.

Each and every one of us has the opportunity to receive light and truth as it is presented to us.  We come under condemnation when we do not live by the truth and light that we know, or when we reject truth when it is presented to us. Notice that by definition this is a step by step process, line by line, principle by principle, doctrine by doctrine until we come to a perfect knowledge of God.

D&C 50:21-24
21 Therefore, why is it that ye cannot understand and know, that he that receiveth the word by the Spirit of truth receiveth it as it is preached by the Spirit of truth?

22 Wherefore, he that preacheth and he that receiveth, understand one another, and both are edified and rejoice together.

23 And that which doth not edify is not of God, and is darkness.

24 That which is of God is light; and he that receiveth light, and continueth in God, receiveth more light; and that light groweth brighter and brighter until the perfect day.

D&C 88:67-68

67 And if your eye be single to my glory, your whole bodies shall be filled with light, and there shall be no darkness in you; and that body which is filled with light comprehendeth all things.

68 Therefore, sanctify yourselves that your minds become single to God, and the days will come that you shall see him; for he will unveil his face unto you, and it shall be in his own time, and in his own way, and according to his own will.

These scriptures plainly point out that a coming to an understanding of the doctrine of the gospel of Jesus Christ is a step by step, line upon line process.  Have any of us come to a perfect understanding of the gospel? NO

Many of us have the false understanding that we have a complete knowledge of the Gospel! 
We should expect and not be surprised when the Lord provides us new clarification and understanding of the doctrines,principles and practices of the Gospel.  We should also expect these revelations to be "Hard" in many cases and difficult to accept or even understand. 
Should that thus cause us to loose our faith and leave the church?  NO

Are there examples of this principle in the scriptures? YES

Jesus Teaches that they must eat his flesh and drink his blood.
John 6:50-69
60 Many therefore of his disciples, when they had heard this, said, This is an hard saying; who can hear it?

61 When Jesus knew in himself that his disciples murmured at it, he said unto them, Doth this offend you?
...
66 ¶ From that time many of his disciples went back, and walked no more with him.

67 Then said Jesus unto the twelve, Will ye also go away?

68 Then Simon Peter answered him, Lord, to whom shall we go? thou hast the words of eternal life.

69 And we believe and are sure that thou art that Christ, the Son of the living God.
Are we to be like those disciples that walked no more with him? This was because they received a doctrine, or commandment that they could not understand or believe and thus lost their faith. Or are we to be like Peter and profess that Jesus has the words of eternal life even if we may not understand the command or doctrine that he has just revealed!! Note that Pride and arrogance - causes this loss of faith.  This was new doctrine to them. This was difficult for them to accept!

Jesus Teaches the Higher Law: 
Math 5:17-48
Wherever you see the words "Ye have heard that it hath been said", what he means by that is your scriptures teach this!  This is what is said in the law of Moses and it is the Law through which you believe you are saved.  Then he says unto them "But I say unto you" meaning that he is giving them a different doctrine, a different commandment, a different law that they should lead their lives by.  This was new doctrine to them.  This was difficult and hard for them to accept... they revered the law of Moses even to the point of killing people who spoke against it!  Yet here was this man that was telling them to not do what Moses said but rather what he said!

Paul is sent to the Gentiles:
Mathew 15:24 - teach only to the Jews
Acts 10:11-35 - teach the gospel to all the world - God is no respecter of persons
The Doctrine of Christ - Ensign April 2012 Todd Christofferson
By this experience and revelation to Peter, the Lord modified the practice of the Church and revealed a more complete doctrinal understanding to His disciples. And so the preaching of the gospel expanded to encompass all mankind.
This was new doctrine to them.  This was difficult for them to accept.

Circumcision is required in the Gospel of Jesus Christ:
Acts 15:1-22 - should circumcision be required?  After much disputing, Peter rose up and teaches doctrine - Paul teaches of Gentile conversion - they accept this doctrine. 
This was new doctrine to them. This was difficult for them to accept.

The Word of Wisdom: Topics
D&C 89 - The word of wisdom was originally given as a principle with a promise.  The Kosher law of the Jews was no longer in force.  There was no law of health that had been provided to the church.  This was new doctrine to them.  Many of the individuals of the church were addicted to substances, tobacco, alcohol, etc.  This as is always the case made it difficult for many of them to live this law.  If you look through the old conference reports of the time there were many of them saying that an individual who went out drinking on Saturday shouldn't consider themselves in that state worthy to bless/pass the sacrament the next day.  To us looking at it from our point of view today it can seem weird yet... it was a challenge to them.

In 1851 Brigham Young asked the saints to commit themselves to live it.  It became a requirement for temple recommends around 1920's.  For a full history see the article at fairmormon.org.  This was difficult for them to accept and live.
"The reason undoubtedly why the Word of Wisdom was given—as not by 'commandment or restraint' was that at that time, at least, if it had been given as a commandment it would have brought every man, addicted to the use of these noxious things, under condemnation; so the Lord was merciful and gave them a chance to overcome, before He brought them under the law. " Joseph F. Smith, Conference Report (October 1913), 14. This was difficult for them to live and accept.  It was after all not a commandment was it.

Blacks and the Priesthood:

During the first two decades of the Church’s existence, a few black men were ordained to the priesthood. One of these men, Elijah Abel, also participated in temple ceremonies in Kirtland, Ohio, and was later baptized as proxy for deceased relatives in Nauvoo, Illinois. There is no reliable evidence that any black men were denied the priesthood during Joseph Smith’s lifetime. In a private Church council three years after Joseph Smith’s death, Brigham Young praised Q. Walker Lewis, a black man who had been ordained to the priesthood, saying, “We have one of the best Elders, an African.”

In 1852, President Brigham Young publicly announced that men of black African descent could no longer be ordained to the priesthood, though thereafter blacks continued to join the Church through baptism and receiving the gift of the Holy Ghost. Following the death of Brigham Young, subsequent Church presidents restricted blacks from receiving the temple endowment or being married in the temple. Over time, Church leaders and members advanced many theories to explain the priesthood and temple restrictions. None of these explanations is accepted today as the official doctrine of the Church.

Note the comment: Church leaders and members advanced many theories to explain these restrictions - none of them are accepted today as the official doctrine of the church!
During the history of the church there have been a few reasons/justifications used for with holding the priesthood from Blacks:

They were either neutral, or not valiant in the pre-existence and thus were blocked from receiving the priesthood.

One such example is found in the following link:
Apostle George F. Richards ( 1861 - 1950 )
Conference Report 1938 pg.58
"The Negro is an unfortunate man. He has been given a black skin. But that is as nothing compared with that greater handicap that he is not permitted to receive the Priesthood and the ordinances of the temple, necessary to prepare men and women to enter into and enjoy a fullness of glory in the celestial kingdom

What is the reason for this condition, we ask, and I find it to my satisfaction to think that as spirit children of our Eternal Father they were not valiant in the fight. .... I cannot conceive our Father consigning his children to a condition such as that of the negro race, if they had been valiant in the spirit world in that war in heaven... Somewhere along the line were these spirits, indifferent perhaps and possibly neutral in the war.  We have no definite knowledge concerning this."

Note that last statement is still part of the quote!

Conference Report 1947 pg. 57 President George F. Richards - President of the Council of the 12 Apostles

The Punishment of the Wicked:
"The Negro race have been forbidden the priesthood, and the higher temple blessings, presumably because of their not having been valiant while in the spirit.  It does not pay to be anything but valiant."

They were of the race of Cain and thus blocked from the priesthood.

Conference Report 1915 - Elder Melvin J. Ballard pg. 62 
"We know, from the doctrines that we have received, that men and women have existed before coming into this life, for countless ages, and that we have been developming certain qualities, and the reason we are separated into great classes, as the Negro race and the other races on the earth, is not a matter of caprice.  God did not take three beautiful children yesterday morning, and say to one, You go to the Negro woman, and to another one, You go to that Chinese mother, and to another you go down to that beautiful christian home.  In my opinion there were classes and races and separation into different groups and conditions before we came to this world, and all are getting what they are entitled to receive here."

The current view of race and the priesthood:

https://www.lds.org/topics/race-and-the-priesthood?lang=eng
This was reviewed in the 1940's and 1950's but President David O. McKay did not feel impressed to lift the ban.

Today, the Church disavows the theories advanced in the past that black skin is a sign of divine disfavor or curse, or that it reflects unrighteous actions in a premortal life; that mixed-race marriages are a sin; or that blacks or people of any other race or ethnicity are inferior in any way to anyone else. Church leaders today unequivocally condemn all racism, past and present, in any form.

Bruce R McConkie Alike unto God - Aug 18, 1978 Devotional

It doesn’t make a particle of difference what anybody ever said about the Negro matter before the first day of June of this year, 1978. It is a new day and a new arrangement, and the Lord has now given the revelation that sheds light out into the world on this subject. As to any slivers of light or any particles of darkness of the past, we forget about them. We now do what meridian Israel did when the Lord said the gospel should go to the Gentiles. We forget all the statements that limited the gospel to the house of Israel, and we start going to the Gentiles.
...
In my judgment this was done by the Lord in this way because it was a revelation of such tremendous significance and import; one which would reverse the whole direction of the Church, procedurally and administratively; one which would affect the living and the dead; one which would affect the total relationship that we have with the world; one, I say, of such significance that the Lord wanted independent witnesses who could bear record that the thing had happened.
...
Now if President Kimball had received the revelation and had asked for a sustaining vote, obviously he would have received it and the revelation would have been announced. But the Lord chose this other course, in my judgment, because of the tremendous import and the eternal significance of what was being revealed. This affects our missionary work and all of our preaching to the world. This affects our genealogical research and all of our temple ordinances. This affects what is going on in the spirit world, because the gospel is preached in the spirit world preparatory to men’s receiving the vicarious ordinances which make them heirs to salvation and exaltation. This is a revelation of tremendous significance.
This doctrine was new to them.  This was difficult for them to live and accept.

This is getting long so I won't put references and history here - but the individual can take as a homework assignment the history of The ordinance of baptism for the dead.
When was it given?
Where were the first baptisms for the dead performed? (hint what river?)
What was the clarification that was received concerning this ordinance? (hint where do we do them now?)
Is the location where these are performed a policy? I think not... it is part of the doctrine of this ordinance.  The manner, the way, the means by which an ordinance is performed is part of the doctrine. (See also water vs wine for use in the sacrament - is this really a policy?  I think not)

Conclusion

These are not all the doctrinal changes that have occurred in the history of the Gospel, and our understanding of the principles and doctrines of the plan of salvation.  We should remember that we believe what it says in Article of faith #9.
Article of Faith #9
9 We believe all that God has revealed, all that He does now reveal, and we believe that He will yet reveal many great and important things pertaining to the Kingdom of God.

There will be yet many great and important things that will come forth, and clarify and give greater understanding to all of the doctrines of the kingdom.  My own hope is that the following doctrines will be clarified: