Now, in theory, you learning from an author's works and competing with them in the same market could meaningfully deprive them of income, but it's a very difficult argument to prove.
On the other hand, with AI companies it's an easier argument to make. If Anthropic trained on all of your books (which is somewhat likely if you're a fairly popular author) and you saw a substantial loss of income after the release of one of their better models (presumably because people are just using the LLM to write their own stories rather than buy your stuff), then it's a little bit easier to connect the dots. A company used your works to build a machine that competes with you, which arguably violates the fair use principle.
Gets to the very principle of copyright, which is that you shouldn't have to compete against "yourself" because someone copied you.
This is one of those mental gymnastics exercises that makes copyright law so obtuse and effectively unenforceable.
As an alternative, imagine a scriptwriter buys a textbook on orbital mechanics, while writing Gravity (2013). A large number of people watch the finished film, and learn something about orbital mechanics, therefore not needing the textbook anymore, causing a loss of revenue for the textbook author. Should the author be entitled to a percentage of Gravity's profit?
We'd be better off abolishing everything related to copyright and IP law alltogether. These laws might've made sense back in the days of the printing press but they're just nonsensical nowadays.
I think, in your example, the obvious answer is no, they're not entitled to any profits of Gravity. How could you possibly prove Gravity has anything to do with someone reading, or not reading, a textbook? You can't.
However, AI participates in the exact same markets it trains from. That's obviously very different. It is INTENDED to DIRECTLY replace the things it trains on.
Meaning, not only does an LLM output directly replace the textbook it was trained on, but that behavior is the sole commercial goal of the company. That's why they're doing it, and that's the only reason they're doing it.
Maybe this is where I'm having trouble. You say "exact same markets" -- how is a print book the exact same market as a web/mobile text-generating human-emulating chat companion? If that holds, why can't I say a textbook is the exact same market as a film?
I could see the argument if someone published a product that was fine-tuned on a specific book, and marketed as "use this AI instead of buying this book!", but that's not the case with any of the current services on the market.
I'm not trying to be combative, just trying to understand.. they seem like very different markets to me.
Because the medium is actually the same. The content of a book is not paper, or a cover. It's text, and specifically the information in that text.
LLMs are intended to directly compete with and outright replace that usecase. I don't need a textbook on, say, Anatomy, because ChatGPT can structure and tell me about Anatomy, and in fact with say the exact same content slightly re-arranged.
This doesn't really hold for fictional books, nor does it hold for movies.
Watching a movie and reading a book are inherently different experiences, which cannot replace one another. Reading a textbook and asking ChatGPT about topic X is, for all intents and purposes, the same experience. Especially since, remember, most textbooks are online today.