James Boyle, law professor at Duke University, says in his The Public Domain: Enclosing the Commons of the Mind:
“[…] the “sweat of the brow” decisions that gave copyright protection based on hard work were not good law. Most courts of appeals had said so.”
This “sweat of the brow” idea neatly encapsulates the romantic conception of the author. He later also calls it “source blindness,” which is less poetic than my spring metaphor, but probably more useful in describing the view of intellectual property which ignores the inherent derivativeness of most creation.
In one conception of creation, the lone auteur produces culture from inspiration and perspiration, and the more inspiration and perspiration involved, the more the author owns the work and has rights controlling what others can do with it. It is a moral right to control your work’s uses, and therefore a difficult one to limit in scope.
In another, authors are standing on the shoulders of giants, ladling from the common well, their work flowing out of their own spring from the hereditary aquifer. It does not matter whether they spend a minute or a lifetime crafting their art, merely that they created it. Their creations are regulated through copyright in the United States was seen as a temporary state-granted monopoly “[t]o promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries.” (United States Constitution).
While both models risks and benefits for creators and society as whole, historically only one had legal standing in the United States: the state-granted monopoly vision of creation. The top one has a lot of emotional value, and probably rings true for many readers.
So, what copyright does the sweat of your brow ensure? The sweat alone grants you no particular rights under the Constitution–it is only creation that matters.
UPDATE: You know when you write an entire paper around a thesis, because it’s so obvious to you that you never state it? That’s what I did in this post. How we view the author matters to fanfiction readers and writers because those writers are authors. If a fanfic author puts more time into a fic than the original author put into the book, does their sweat earn them anything? How much do they own of their own writing? It is unclear under either conception, but they will only be sued/protected under one. Making sure it is the healthiest standard possible benefits any fan.