What’s an idea, you might ask?
I have no idea. The copyright office doesn’t offer a definition. The copyright office does say this (same link as above):
How do I protect my idea?
Copyright does not protect ideas, concepts, systems, or methods of doing something. You may express your ideas in writing or drawings and claim copyright in your description, but be aware that copyright will not protect the idea itself as revealed in your written or artistic work.
This site is a bit gimmicky, but the guy who wrote it purports to be a patent attorney, and he expresses the difference between an idea and a patentatble (or by extension, copyrightable) item:
Ideas are a dime a dozen. What is valuable is not the idea that it would be wonderful to have this or that functionality, but rather the valuable piece to the puzzle is how to specifically provide that functionality you identify.
There’s so much snake oil on the Internet when it comes to patents and copyright (imagine that) it’s hard to sort the truth from the marketing gimmicks.
Yet here is another explanation that mirrors the one from above.
Paraphrased: Two people coming up with the same idea and writing articles based on said idea aren’t copyists or plagiarists for using the same idea. If one mirrored wording from the other’s article, that’s plagiarism. Writing on the same topic is not.
So the guy who put this anti-copyright disclaimer in his book is half right. You can’t own an idea. But I’ll wager if someone went around handing out free copies of his book – even if it was meant as flattery – he might have issues with that.
Also, copyright law does not restrict the free flow of ideas, as ideas cannot be copyrighted. Copyright protects authors, such as this one, from anyone copying his work and selling it as their own. To think otherwise is to think you can put your dirty feet on the table in proximity to someone’s food, and then argue that it’s not really their food.