I'm getting bored with the obligatory lesson every time we begin a study on the Book of Mormon which involves the teacher drawing a very poor diagram of an arch on the board and explaining the importance of a keystone. This year we are subjected to the convention twice, once in Sunday School Lesson #1 and now in the JS Manual Lesson #4.
Just FYI on keystones: A keystone is the architectural piece at the crown of a vault or arch and marks its apex, locking the other pieces into position. Although a keystone is important, it serves primarily an aesthetic purpose. Some say that a keystone is not as important structurally as the voussoirs, since the removal of any of the voussoirs would cause the arch to collapse but this is not necessarily true of the keystone. A keystone is not the main load-bearer in an arch. The stresses are greatest at the bottom and least at the top. The forces along the center line are horizontal, so an arch can work perfectly well with an even number of voussoirs, and no keystone at all!
Joseph Smith's statement that the Book of Mormon is the keystone of our religion is no more than a figurative and not strictly legitimate use of the term to suggest that the book is the central supporting element of the larger structure of the Church. In our lessons we are stretching the metaphor to the point of being grossly inaccurate. (Besides that, I like to think of Christ as the central element.)
Now I wouldn't have any problem if a qualified architect or mason came to SS prepared to discuss the intricacies of archwork and new applications we could bring to the metaphor. For example, here's an interesting definition:
The keystone is the block without which the structure is not whole; it receives and joins forces of upwardly-reaching members of an arch and creates a structure that soars with lightness yet with solid integrity and strength. The integrative strength of the keystone is a natural one that does not depend for its function on massiveness but rather works because everything falls into place around it and is strengthened and brought together by it, making all the components work together. A keystone is synergistic, yielding a structure that is stronger than the individual parts would be if they were merely stacked together, one on top of the other. It exists to unite structural elements.
But I think I'd rather just drop the overemphasis on this old chestnut. There are more fascinating things in this lesson to discuss. Tomorrow I will blog about one of them.