Why were the New Testament books arranged in the order they are?

Answer 1

The gospels were considered the most important and the first, chronologically, so they were placed first. They were once thought to have been written in the order, Matthew first, then Mark, Luke and John, thus dictating the order of the gospels in the New Testament. Acts of the Apostles followed, because it was seen as a natural extension of the gospels.

Paul's epistles were considered the most important of the epistles, so they followed the gospels and Acts. With one minor exception, they were placed in descending order by size. Hebrews was thought by some to have been written by Paul, so it was placed with his epistles, but after the others attributed to him.

The remaining epistles followed, again in order by size, while keeping epistles thought to be by the same author together.

There was much early dispute about including Revelationin the New Testament, and in early times it was considered the least important book of the New Testamant. This justified its last place, but it also represents a different genre, which had to be third.