What is the/a word to describe an overly-authoritative author/writer?

What is/are the word(s) for a person who writes/speaks with the attitude of always being right, having the final answer(s), never having their position or interpretation questioned, having the final say on a subject? One who positions him- or herself as the ultimate and final authority on a subject, who entertains no possible alternatives to their interpretation of a subject? "He writes as though he is the ______ on this topic." Not the authority, but a word meaning the presumed authority - seeing this as a negative trait.

Solution 1:

One possible expression is that he thinks he's "the last word" or "the final word" on the subject. There's another question about that phrase (with pertinent examples).

Another term that comes to mind is "the be-all and end-all." This is defined in an "often jocular" sense as "a person or thing considered to be beyond improvement."