Disputations are differences of opinion inside the church. In the Book of Mormon, contentions were differences of opinion between believers and non-believers in Nephite society. When internal contentions disrupted Nephite society, the causes were conflicts between the traditional Nephite religion and the “outside” religions of the non-Nephites (and typically of some form of Nehorite religion).
In contrast to contentions, disputations occur completely internal to the church. These are arguments within the church, that may or may not have any relation to the outside religion. There is no direct competition with a foreign religion, even though some of the ideas from the foreign religion might be entering Nephite faith.
In 3 Nephi, the Savior notes that there are been “disputations among you concerning the points of my doctrine.” (3 Nephi 11:28.) The address is to those who are in Bountiful, who by textual definition are the believers. Thus these disputations are indicated as existing among the faithful, and specifically concerning points of Christian doctrine (my doctrine).
A specific example of disputations arises when the believing community cannot come to an understanding of the name for the church (see also the commentary following 3 Nephi 27:3).
3 Nephi 27:3
3 And they said unto him: Lord, we will that thou wouldst tell us the name whereby we shall call this church; for there are disputations among the people concerning this matter.
This issue of internal dissention is not an issue prior to the arrival of the Messiah because the threat to the Nephite religion prior to that time was so heavily external. After the arrival of the Savior, however, the church is formed with even more structure, and apparently even more independence from governmental issues. The result is that there is both a greater potential for disputations, and there become a larger set. It is interesting that when Mormon needs to describe the near-millennial period after the Savior’s arrival in the New World, one of the specific comments about that idyllic time is the absence of disputations.
4 Nephi 1:2
2 And it came to pass in the thirty and sixth year, the people were all converted unto the Lord, upon all the face of the land, both Nephites and Lamanites, and there were no contentions and disputations among them, and every man did deal justly one with another.
Although Mormon does not explicitly discuss the dissolution of Nephite religion from the “perfect” state of no disputations to the eventual existence of many disputations, it follows the same spiral of apostasy that he describes for Nephite society, where their eventual state was the loss of the millennial conditions for the first nearly two hundred years after the Savior appeared in the New World.