Our writers' group watched another section of a video of William Bernhardt's seminar on novel writing. Several times during his amusing and informative talk he mentioned outlining, always followed by the statement, "and you will outline." According to Bernhardt, all novelists outline, even those that claim they don't. He offered the opinion that some writers think that admitting to using an outline suggests a lack of creativity or spontaneity in their writing.
I think it's true that all novelists outline in some form or fashion. I don't see how anyone can write a fiction book without some kind of organizational method for keeping track of "what happens when" in the story. Many writers may not think of their system of notes as an outline, but it serves the same purpose.
The word "outline" suggests having the plot of a book all planned out before the writing begins. Many writers do have a good enough idea about their book that they can create an outline first. But nearly all writers that do so will - and know they will - make changes to the outline as the book progresses and deviates from the original.
Authors who claim not to use an outline, or call their outline process something else, are more likely to be the ones that don't outline before they write; writers like myself, who don't know enough about where the story is going to lay it all out before hand.
I call what I do a timeline. And I don't bother with it until I have a clear idea of what the main story events are, but not the best order. That's when I put each scene on an index card and move them around in different patterns to find the one that works best. Then I write out the order of scenes, so I can keep track of "what happens when" and adjust as necessary.
So, yes, if you are writing a novel, you will outline. Even if you say you don't, you do - in your own way, however such a thing fits in you personal writing process.