While the occurrence of a general apostasy is a matter of belief and not observable by historical inquiry, dispensations are born with a burst of documentary evidence. This makes the dispensation, a not entirely unique but yet very Mormon way to draw historical boundaries, a useful concept that could be applied to the periodization of many other endeavors.
In a Mormon context, what we see as a breach in priesthood authority between late antiquity and antebellum America maps very neatly onto a similar and readily observable breach in textual authority within Mormon thought. From the early church fathers to the scholastics and the various Protestant reformers and their descendants, there are nearly two millennia of Christian writing that are almost totally irrelevant to Mormon concerns. What did Augustine or Anselm think about grace? The Mormon answer is: who cares? We don’t recognize any authority in their writings. In the context of Mormon questions about what we ought to believe, or how we should behave, the journal of an obscure nineteenth-century apostle holds a hundred times the weight of the profoundest writings of Christian history, and a clip-out truism from the latest Ensign holds yet a hundred times more significance. I don’t intend to criticize the Mormon ignoring of Augustine, but only to note that it is easily observed. The Dispensation of the Fullness of Times, a Mormon theological term for the years after ca. 1820, is a readily observable fact in the ways Mormons deal with pre-Restoration texts.
There are a few, relatively uncommon exceptions. Occasionally, pre-modern writers are pressed into teleological service as pioneering anticipators of the dispensation to come. John Wycliffe and Martin Luther are useful to Mormons only in the areas of overlap, however limited or strained, between their thinking and Mormon thought. The other exception, mostly confined to Mormon apologetic scholarship, mines earlier writers for evidence of incipient or persisting apostasy. (Did you hear what Origen did to himself?) But if something written before 1820 neither supports us nor offers a shocking contrast, it is entirely uninteresting. As a medievalist I should probably be disappointed, and I do think that we could use an approach to the Middle Ages that was more nuanced and charitable towards several centuries of human existence.
But the curtain we drop over 1700 years of history is actually, I think, one of the aspects of Joseph Smith’s genius. He drew a line through the account books of Christian intellectual history and let us start over anew, unburdened by an unbearable weight of tradition. We can create a new spiritual and intellectual tradition. Or we can re-invent the wheel, or re-fight the religious bickering of the last two millennia, if that is what we choose to make of the opportunity.
Of course there is much useful material in all those old books, and sometimes we need to import it into Mormonism in a way that makes it useable not just for scholarship but also for devotion. The political interpretation of Nebuchadnezzar’s dream as referring among other things to the Roman Empire and later European nations is very old but not in itself scriptural, which makes it of little use to Mormon devotion—until Spencer W. Kimball cites it in conference, after which the Old Testament lesson manual can ascribe the idea to him. What would you do if the world were ending tomorrow? I would plant an apple tree, said Martin Luther, in a well-known quotation. Or a cherry tree, according to Wilford Woodruff. That these ideas are much older than our modern prophets is, as far as devotion is concerned, nothing more than a historical footnote.
The Mormon concept of dispensation is terribly ahistorical, one might object. Surely everything comes from something previous, and former centuries had their own purposes beyond preserving relics of the past, or anticipating the future for the benefit of the present.
But the Mormon practice of drawing dispensational boundaries only makes visible, I think, what is an all but universal practice. One of the aims and accomplishments of the American Revolution was to sever the authority of English law, and ever since then the earlier jurisprudence has become a historical footnote rather than a decisive factor in determining the fate of human lives or billions of dollars. Linguistics before William Jones, or Saussure, or Chomsky is a curiosity cabinet, rather than a source of insights on how language works. When exosolar planets are discovered, astronomers compute their orbits, not their epicycles. German literature gets rebooted in 1150, and 1750, and again in 1945, with most earlier authors holding little exemplary value for later ones. Methods of literary criticism older than a century are today considered more embarrassing than useful. Even Martin Luther’s statement of resolve to plant a cherry tree can be traced back no further than 1942; Lutheran theology also seems to have dispensational boundaries that occasionally must be breached.
To what extent documentary evidence maps onto divinely-acknowledged borders between eras remains, of course, a matter of faith. But evidence for the human perception of dispensations can be found everywhere.