As an outstanding preacher himself, Eugene had no patience with the flowery preachers who had style and played with words but had no solid content. His diary entries spare them no criticism, and in his Rule he wanted to ensure that his Missionaries never fell into this trap.
It should be understood that it is in direct opposition to the spirit of our Rule to aim at elegance of style in preaching, rather than solidity of doctrine.
Too many preachers want to be admired for the magnificence of their eloquence and the brilliance of their studied language; we must follow another way;
1818 Rule Part 1, Chapter 3, §1 Preaching