No, you don't understand what I'm saying. I literally said general knowledge (ie, facts) isn't applicable.
Math is unalienable. No matter who does the math, 2 + 2 = 4. The math itself cannot be plagiarized. The interpretation of that math, can be, as well as how it is explained. A math textbook can be plagiarized, because all textbooks are interpretations of facts. You know how A² + B² = C²? That's the Pythagorean theorem. It's taught as the Pythagorean theorem because Pythagoras discovered/invented it. We credit him every time we use the name. Likewise, everyone knows Einstein discovered E = mc². But saying A² + B² = C² or E = mc² doesn't mean anything without the interpretation.
History is completely different than math, because history is not unalienable. You think history is X happened, Y wrote it down exactly as it happened, end of story? No. That's not how history works, at all. All history is interpretive. Most history is also speculative. People discover new historical evidence all the time. That evidence then gets interpreted by a scholar. The evidence itself may be general knowledge, ie, facts. The interpretation of that evidence is intellectual property that can be plagiarized.
I tried to use a simplified example to help you understand, since you clearly don't grasp what plagiarism is. No metaphor is perfect! Obviously it's not a 1:1 equivalence. But intellectual property is still property. Just because it can be copied without diminishing the original doesn't make it not valuable.
In fact, the metaphor does work on the level you say it doesn't, because copying intellectual property inherently devalues it, reducing the "amount" left for the owner. For example, say I write an ebook that I sell for $3. The market for this book is 1 million people, so has a potential value of $3 million. Someone copies my book and sells it for $1. Now the value is $1 million. The value of my book has decreased, because it has been stolen. Same with the copper pipes: someone has stolen some of my copper, I now have less potential value if I were to sell my own pipes. You're right that my book can be stolen 1000 times-- doesn't that make the theft of intellectual property worse than physical theft, because it decreases inherent value in perpetuity?
