Now, before I start, I need to make an important distinction between the theory that when we achieve exaltation, we return to a mortal world to make physical bodies for our spirit babies (essentially the Adam-God theory) and the doctrine of Multiple Mortal Probations, which is the idea that before we achieve exaltation, we go through mortality several times in order to become more righteous and holy.
Ok. Let's get stuck in. "When the elements in their organised form do not fill the end of their creation, they are thrown back again, like Brother Kimball's old pottery ware, to be ground up and made over again" .
Now, it is far from clear as to exactly what this delightful little quote from Brigham Young means. One interpretation is certainly consistent with Multiple Mortal Probations - if we do not attain the standard of righteousness required in this life, we will be reincarnated, either on this planet or another, to be purified further, and that this process will continue until we attain Godhood. However, this is far from the only way to interpret this quote. "The elements in their organised form" could simply refer to the physical universe, however it is unclear, if God is in control, when the physical elements would ever "not fill the end of their creation", so I think that this interpretation is unlikely. A third position would be to say that "the elements in their organised form" refers to spirit bodies. This would imply that those who deny the Holy Ghost and become Sons of Perdition are esentially 'recycled' - not only their physical body, but also their spirit body is taken from them and recycled to make spirit bodies for other intelligences. This quote has certainly been interpreted that way before, and I think it is definitely a valid interpretation, although most mainstream Mormons probably aren't too familiar with the idea of recycling Sons of Perdition.
Another interesting pearl from the Journal of Discourses is this statement by Heber C Kimball: "If you do not cultivate yourselves, and cultivate your spirits in this state of existence, it is just as true as there is a God that liveth, you will have to go into another state of existence, and bring your spirits into subjection there. Now you may reflect upon it, you never will obtain your resurrected bodies, until you bring your spirits into subjection. I am not talking to this earthly house of mine, neither am I talking to your bodies, but I am speaking to your spirits. I am not talking as to people who are not in the house. Are not your spirits in the house? Are not your bodies your houses, your tabernacles or temples, and places for your spirits? Look at it; reflect upon it. If you keep your spirits trained according to the wisdom and fear of God, you will attain to the salvation of both body and spirit. I ask, then, if it is your spirits that must be brought into subjection? It is; and if you do not do that in these bodies, you will have to go into another estate to do it. You have got to train yourselves according to the law of God, or you will never obtain your resurrected bodies. Mark it!".
One of the biggest disadvantages to statements in the Journal of Discourses is that they often have the feel of communicating a message of great importance without being all too clear about what exactly that message is. This statement is no exception. While this could certainly be interpreted as an example of the doctrine of Multiple Mortal Probations, this is by no means the only interpretation. It could very well simply be teaching the rather standard, mainstream Mormon doctrine that we continue to progress in the Spirit World after this life (although the implication in the second-to-last sentence that we need to earn our resurrected bodies is clearly in conflict with modern LDS teachings). For example, the only thing that this quote unequivocally declares is that if we do not "cultivate [our] spirits" in this state of existence, we will have to do so in another state of existence, with no clear indication of what that state of existence is. However, he seems to imply that the state of existence he refers to is one where our spirit is combined with a body of some kind when he states: "If you do not do that in these bodies, you will have to go into another estate to do it", and he does explicitly say: "I am not talking as to people who are not in the house [ie. disembodied spirits]". So, all in all, I would suggest that, reading this quote with a completely open mind, the most likely interpretation is that this is indeed an example of Heber C Kimball teaching the doctrine of Multiple Mortal Probations, with the recognition that this is by no means the only possible interpretation, merely the most obvious and the most likely.
So, what have we got so far? Two rather mysterious passages from the Journal of Discourses, one which most likely teaches the doctrine of Multiple Mortal Probations, and one which is far less explicit. Let us see if there is anything else lurking around somewhere in the junkyard of discarded Mormon theology that might support this intriguing and fascinating doctrine.
As far as my research has suggested, it seems to me that perhaps one of the clearest, most prominent sources for the doctrine of Multiple Mortal Probations is Heber C Kimball. So far, he has provided us with what is by far the clearer of the two quotes regarding this doctrine that we have come across so far, and he is also the author of what is perhaps the clearest, most explicit teaching of the doctrine to be found in the Journal of Discourses: "What I do not today, when the sun goes down, I lay down to sleep, which is typical of death; and in the morning I rise and commence my work where I left it yesterday. That course is typical of the probations we take. But suppose that I do not improve my time today, I wake up tomorrow and find myself in the rear; and then, if I do not improve upon that day, and again lay down to sleep, on awaking, I find myself still in the rear. This day's work is typical of this probation, and the sleep of every night is typical of death, and rising in the morning is typical of the resurrection. They are days' labours, and it is for us to be faithful today, tomorrow and every day. Brethren, this is the course we have to take; it is a progressive work from one day to another, and from one week to another; and if we advance this year, we are so far advanced in preparation to better go through the next year. If I have one thousand bushels of wheat laid up this year, can you not understand that I am better qualified to lay up two thousand bushels during the next year? And then in the succeeding year I am better prepared to add four thousand bushels to my amount on hand, and then eight thousand, and so on". I challenge anyone to read that and not have an overwhelming impression of Multiple Mortal Probations. Kimball uses the analogy of going down to sleep as being symbolic of death, and rising again as representing a return to life. What is most interesting is that he does this in the form of the parable. He tells a hypothetical story: "I do not improve my time today, I wake up tomorrow and find myself in the rear; and then, if I do not upon that day, and again lay down to sleep, on awaking, I find myself still in the rear", and then he goes on to explain the parable, by identifying the symbolism present in the parable. Because, in the hypothetical story (the parable), we lay down to sleep more than once, and arise more than once, I would argue that the most probable interpretation of what Heber is trying to illustrate here is that he is teaching the doctrine of Multiple Mortal Probations. This is further reinforced by the fact that straight after explaining that what he means by a 'day' is a mortal probation, ending with death and then commencing anew again, he goes on to say: "They are days' [note the plural] labour, and it is for us to be faithful today, tomorrow and every day". The "every day" concept certainly implies more mortal probations than just "today" and "tomorrow". Of course, in both of the examples I have used of Heber teaching Multiple Mortal Probations, one difficult issue to explain is the references he makes to resurrection and resurrected bodies, which is something I hope to grapple with later in this post. However, I still believe that these statements by Heber C Kimball, if read with a completely open mind, are most accurately interpreted as examples of Heber teaching the doctrine of Multiple Mortal Probations.
It gets better. Consider this entry in the diary of Orson F Whitney: "3 June 1889: This evening I heard that Pres. Woodruff, in a meeting at Manti, a few days ago, publicly declared that the doctrine of reincarnation, that is one spirit having several bodies, to be false; that he was Wilford Woodruff and no one else, &c &c. Alright, bro. Woodruff, if you really said it, it is between you and the Lord. I believe it to be a true doctrine, & have for the last [word cut out of entry] years". From this entry, it is fairly clear that the doctrine of Multiple Mortal Probations (or reincarnation as it is referred to here) was firmly believed for a number of years by at least one General Authority of the Church, and the fact that President Woodruff felt the need to publicly declare the doctrine false also suggests that it was believed by a number of people.
By the way, we can substantiate the claim that Wilford Woodruff preached against the doctrine of Multiple Mortal Probations. It is likely that the denunciation that Whitney refers to is the one recorded in the Deseret New Weekly: "I have heard that in Zion there are some men who entertain the idea that they inherit the body and spirit of Moses, or Abraham, or David, or Noah, or somebody other than themselves. I hope none of you here indulge in anything of this kind, because it is a most foolish, nonsensical and false doctrine. You gaze upon a man who professes to have inherited the body or spirit of Moses, or any of those I have named, and I think you will conclude that his appearance does not indicate that such is the case; at any rate, it certainly has not improved him. Brother Woodruff, Brother Cannon, Brother Smith, Brother Lorenzo Snow, or any of the brethren, will never inherit anyone's body or spirit but their own, in time or in eternity, unless the devil gets into them. It is Satan who inspires men to believe in such absurd things. He delights in having any of the brethren entertain false ideas, no matter what they are. I tell you that whoever sees me in time or in eternity will see Wilford Woodruff, not Noah, nor Abraham, nor Enoch. Every man has his own identity, and he will never lose that identity. Therefore, when you hear such doctrine as that advanced, do not believe it. There are a good many things Satan would like us to believe; but we must guard against these" . Now, Wilford Woodruff here seems to conflate and confuse a fair number of quite different doctrines. However, I think it can be quite clearly concluded that somewhere in this rant President Kimball unequivocally denounces the doctrine of Multiple Mortal Probations, as well as a few other related theories.
So, in my mind, I'm gradually building up a picture of where some of the General Authorities of the 19th Century stood on this issue. Brigham Young: possibly believed and taught it, although this is a very big maybe. He made a couple of statements that might lead one to suspect that he was implying some form of Multiple Mortal Probations, but he also made several statements that appear to be completely incompatible with such a doctrine. I defy anyone to state with certainty what Brigham actually believed about anything; he both taught as doctrine and refuted as heresy pretty much every possible theological concept you can think of throughout his presidency. Heber C Kimball: most likely believed and taught it. Again, it's difficult to be certain, but a couple of his sermons would indicate such a stance. Orson F Whitney: definitely believed it. Wilford Woodruff: certainly did not believe and publicly preached against it.
The Church during the 19th Century, similar to the early centuries of the Christian Church, was a Church racked with doctrinal controversy and debate. And one of the favourite ways of adding an extra stamp of authority on to your particular theological idea was to say it originated with Joseph Smith. Multiple Mortal Probations is no exception. A mere five days after the above entry, Orson F Whitney writes: "8 June 1889: During our talks he [Lorenzo Snow] told me that his sister, the late Eliza R. Snow Smith was a firm believer in the principle of reincarnation and that she claimed to have received it from Joseph the Prophet, her husband. He said he [Lorenzo Snow] saw nothing unreasonable in it, and could believe it, if it came to him from the Lord or His oracle." . This is very interesting indeed. Similar to the Adam-God theory, which Brigham Young claimed he first heard from Joseph Smith, there is no way of either confirming or falsifying Eliza's claim. Joseph was certainly teaching a lot of new and astounding doctrines, both in private and in public, during the Nauvoo period, but if he ever did teach it, we have no record of it besides Eliza's word. What this entry does prove, however, is that both Eliza and her brother Lorenzo Snow were believers in the doctrine of Multiple Mortal Probations. So we can add them to the growing list of believers amongst the 19th Century Church leadership.
One issue that we must grapple with regarding a fair few of these teachings by prominent early Church leaders revolves around the fact that many of them speak of Multiple Mortal Probations and the resurrection (or, in Heber C Kimball's case resurrections) in the same breath. Which leads us to the question of...how does resurrection fit into all this? Most of us will be familiar with the analogy of the glove, taught to Primary children and investigators: at birth, our spirit (represented by a hand) is placed into our body (represented by a glove). Then, at death, our spirit and body are separated (our hand is removed from the glove), and at the resurrection, our spirit is reunited with this body, which is transformed into a perfect state (represented by the hand once more being placed into the glove). This resurrection will take place at the Second Coming of the Saviour.
So how can Multiple Mortal Probations be reconciled with resurrection? Early Church leaders had fairly diverse beliefs regarding the nature of the resurrection, as is evidenced by this entry in the journal of William Clayton: "It was finally moved and carried viva voce [by word of mouth], that the doctrine of the Resurrection be the subject to commence with, and the following Brethren expressed their views in regard to it viz. Charles Smith, Jesse Turpin, George Mayer, James Park, David Wilkin, Edward Stevenson, and Edward Bunker. The views of these Brethren seemed to vary materially on the subject, and there was very little or no light manifested by any one. It appears that the great difference in the views, is in regard to what is commonly called the baby resurrection, which idea is, that instead of the bodies being raised out of the ground &c. we shall again be born of a woman, as we were when we came into this world. Brother James Park agreed very strongly in favor of this kind of doctrine. This was a matter of astonishment to me, as I had never before heard of such a doctrine to understand it". This would seem to indicate that closely tied up with the doctrine of Multiple Mortal Probations was a model of resurrection that simply saw resurrection as the union of a spirit and a body - and not necessarily the same body that one's spirit inhabited previously. In light of this concept of the resurrection, Heber C Kimball's analogy of going to sleep and waking up to continue your work where you left it yesterday makes perfect sense, as does his implication of multiple 'resurrections'. In that framing, each time we begin another mortal probation, we are essentially 'resurrected'.
Of course, Heber C Kimball's statement: "You have got to train yourselves according to the law of God, or you will never obtain your resurrected bodies" becomes somewhat problematic if resurrection is seen as merely the reunion of body and spirit, and if Heber's discourse from which this quote is taken is read as a sermon on Multiple Mortal Probations. However, one possible explanation of this would be the possibility that what Heber meant by a resurrected body was not in fact just another mortal body, but rather an immortal one - a glorified, perfected, restored, exalted body of flesh and bones, of the same variety of the Father's.
WHY I LIKE THE IDEA OF MULTIPLE MORTAL PROBATIONS
There is no denying that Multiple Mortal Probations was believed and taught by some Church leaders in the 19th century. But does the idea have any scriptural support? Moses 1 is a key text when it comes to exploring these issues. In fact, it is something of a goldmine for deep speculative theology. It would take too long to quote the entire chapter here (though I am tempted to do so), so instead I'll just say you should all go read it and spend a good deal of time seriously considering it, and quote the most pertinent part: "4 And, behold, thou art my son; wherefore look, and I will show thee the workmanship of mine hands; but not all, for my works are without end, and also my words, for they never cease..33 And worlds without number have I created; and I also created them for mine own purpose; and by the Son I created them, which is mine Only Begotten...35 But only an account of this earth, and the inhabitants thereof, give I unto you. For behold, there are many worlds that have passed away by the word of my power. And there are many that now stand, and innumerable are they unto man; but all things are numbered unto me, for they are mine and I know them...37 And the Lord God spake unto Moses, saying: The heavens, they are many, and they cannot be numbered unto man; but they are numbered unto me, for they are mine. 38 And as one earth shall pass away, and the heavens thereof even so shall another come; and there is no end to my works, neither to my words. 39 For behold, this is my work and my glory - to bring to pass the immortality and eternal life of man." Now, there is nothing in this entire chapter that explicitly teaches Multiple Mortal Probations. The way these verses are traditionally interpreted is something along these lines: God has a whole lot of children. God sends some to one planet, some to another, and some to another, and so on etc. His work and His glory is to bring to pass the immortality and eternal life of every single one of His children on every single one of His innumerable inhabited planets.
That is a perfectly valid interpretation of Moses 1. However, another interpretation which is consistent with Multiple Mortal Probations centres around the assertion that "as one earth shall pass away...even so shall another come". One way of reading this would be that, in God's efforts to give us ample opportunity to become exalted, He sends us to earth in order to learn and grow from the specific trials we experience here. Then, when we have learned all we can on this earth and grown all we can, we die and are reborn on a new earth, with new trials and adversity to experience to act as a catalyst for further growth, learning and development. Thus, "as one earth shall pass away...even so shall another come" all in order for God to bring about His work and glory - "to bring to pass the immortality and eternal life of man".
Another reason I quite like the Multiple Mortal Probations concept is that it strikes a resonant chord with LDS beliefs about eternal progression. According to traditional LDS theology, there are two primary reasons that we chose to come to earth: firstly, to gain a physical body, and secondly, to learn and grow. The fact that the second reason is necessary is demonstrated by the fact that we do not die as soon as we have gained a physical body. Therefore, if we had to experience the trials, tribulations and adversity of mortality in order to learn and grow (the traditional Irenaean theodicy espoused by the LDS Church), this would imply that learning, growth and progression is only possible in a state of mortality. If this is so, then the implication is that we would cease to learn and grow upon our death - "that same spirit which doth possess your bodies at the time that ye go out of this life, that same spirit will have power to possess your bodies in that eternal world", except that spirit will be essentially stuck eternally at a spiritual plateau. With none of the trials, tribulations and adversities of mortal life, they will never be able to continue growing and learning. This flies in the face of the whole concept of eternal progression. If this is true, then in order to become Gods we must be perfect by the time of our death. Since I don't think anyone completely attains perfection in this mortal probation, we must face the fact that without Multiple Mortal Probations, it is unlikely that anyone will ever attain perfection and become exalted except the Saviour (who is a bit of an outlier anyway, since He was already exalted before He came to the earth). This conclusion is extremely uncomfortable for me, as it clashes with the entire King Follet Discourse, not to mention several passages from the Doctrine and Covenants (such as Section 132), Book of Mormon (such as 3 Nephi 12), Old Testament (such as Psalm 82), Pearl of Great Price (such as Moses 1) and New Testament (such as John 10), and hence I choose to embrace the concept of Multiple Mortal Probations.
CONCLUSION AND IMPLICATIONS
We can most assuredly conclude that Multiple Mortal Probations was a doctrine taught and believed by at least some early Church members, including a fair few prominent Church leaders. What seems less clear is whether or not we experience these Multiple Mortal Probations on the same planet/level of existence, or whether we progress to higher planes of existence with each successive probation (or, alternatively, when we attain a level of spiritual health and righteousness that is sufficient and appropriate for the lessons we have learned throughout our life/lives on this planet or level of existence and we become ready for new opportunities for growth and development in 'holier spheres'). This is an issue that doesn't seem to be clearly spelled out by early Church leaders. I personally feel that the second possibility is more in line with the central Mormon principles of eternal progression and an infinitely graded cosmology, although this is a conclusion that is far from clear in the writings and sermons of early Church leaders.
Ultimately, I think the doctrine of Multiple Mortal Probations, while clearly at odds with a lot of LDS Scripture and clearly denounced by a number of Church leaders as foulest heresy, nevertheless makes much more sense and feels a lot fairer than the idea that God will refuse the earnest seeker after righteousness the opportunity to return to mortality for more 'soul-making' and opportunities for spiritual growth. Which brings up another question - are we perhaps given the choice to undergo another Mortal Probation? This would certainly be more in keeping with a theology that radically prizes agency and choice as possibly one of the most important and fundamental things when it comes to morality.
All things considered, I quite like the idea of Multiple Mortal Probations. I regret that the Church has so vehemently denounced it, although of course I can understand why they would do so - it is, after all, radically at odds with the vast majority of LDS scripture. When all is said and done, I have enjoyed the experience of delving into Multiple Mortal Probations, and regardless of whether or not it has a place in modern Mormonism, I have found the experience of studying its history and considering its implications within a Mormon framework to be both illuminating and intriguing, and it has certainly provided me with some food for further thought!
 - Brigham Young, Journal of Discourses, Volume 1, pp 275-276
 - Heber C Kimball, Journal of Discourses, Volume 1, p 356
 - Heber C Kimball, Journal of Discourses, Volume 4, p 329
 - Diary of Orson F Whitney, 3 June 1889 entry
 - Deseret News Weekly, 38:822-24, Collected Discourses, 1:262-263
 - Diary of Orson F Whitney, 8 June 1889 entry
 - An Intimate Chronicle: The Journals of William Clayton, pp 429-430, edited by George D Smith