On the Sublime Longinus, like Horace, takes a pragmatic position. OK, so far that isn't terribly helpful. Good writing takes part of the good.
Sublimity is a certain distinction and excellence in expression.
Well . . . that's a little better, but not much. This is still somewhat nebulous, but it gets clearer along the way. Great accents we expect to fall from the lips of those whose thoughts are deep and grave. These great men capable of great ideas will also be capable of deep and sincere feeling which transcends the mawkish emotions of parenthyrsus.