Raymond Treat reports that much linguistic evidence has come to light since 1830 supporting the Book of Mormon as an authentic document. One of the more recent such discoveries (Welch 1969) is the recognition that some writers in the Book of Mormon used an ancient literary form known as chiasmus or a chiasm.
A chiasm is a statement containing two or more parts followed by a restatement in reverse order (ABC C'B'A'). The word chiasm is derived from the Greek letter chi (X) and the Greek word chiazeim (to mark with an x) because a two part chiastic statement may be diagrammed in the form of an X.
Dr. Noel Freedman, Ph. D., Director of Program on Studies in Religion, University of Michigan and General Editor of the Anchor Bible and Biblical Archaeologist discusses two kinds of chiasms in his preface to Chiasmus in Antiquity. One kind deals with words and the other with ideas. The type dealing with words is easily identified. There is generally no argument as to the existence of this type of chiasm. The words which are inverted or balanced can either be the same, synonyms or antonyms. An example from the Book of Mormon is found in Mosiah 3:18-19: "But men drink damnation to their own souls, except
A. they humble themselves
B. and become as little children,
C. and believe that salvation was, and is, and is to come, in and through the atoning blood of Christ,
the Lord Omnipotent:
D. for the natural man
E. is an enemy to God
F. and has been, from the fall of Adam,
F' and will be, for ever and ever;
E' but if he yields to the enticings of the Holy Spirit,
D' and putteth off the natural man,
C' and becometh a saint, through the atonement of Christ, the Lord,
B' and becometh as a child,
A' submissive, meek and humble . . ."
The last six points parallel or repeat the first six points in reverse order, therefore, chiasm is also defined as an inverted parallelism. [Raymond C. Treat, "Chiasms in the Book of Mormon," in Recent Book of Mormon Developments, Vol. 1, p. 64]