I would try by saying every author is a compiler (as in, a collector of sources). They use someone else's ideas, either as building blocks or as a subject. The rules for when and how the people down the chain should be compensated are arbitrary. For a long time it wasn't a problem anyone cared about in societies (the pre-copyright era), then we got sort of a "verbatim" standard, but we're seeing more and more how silly it always was with better tools of automatic rephrasing.
Publishing books in the current model is like planting flowers in a public space, with seeds you've just taken from a bunch of other people's houses, and then requiring people who walk there or look at the flowers to pay you. I mean, we should be encouraging caring about the commons in some way. But the creators or copyright holders for cultural creations don't inherently have the power to dictate the schemes they like.
It isn't that there is no original work in using the existing sources. Just more stuff is, by necessity, re-used that created (otherwise people wouldn't understand you), and the exact boundary is arbitrary.
Given the choice, many people would rather get something for free rather than pay for it. Rather than simply admitting that there is something at least a little immoral about benefiting from someone else's work without paying for that work, they come up with elaborate rationalizations.
There's a sort of virtue in embracing the intellectual honesty of saying that you took that work because you wanted it and had the means. Call it the Genghis Kahn justification.
Even if the work is completely derivative, someone still put significant effort into compiling and organizing it. And their immorality of taking the work of others doesn't obviously justify the immorality of taking theirs.
The point is, it wasn't immoral of them to "take the work of others" to begin with. This is how culture works: mythology, classic stories like the Arthurian cycle, fables, lots of classic literature etc. came to be by just taking the stories and characters people liked and doing whatever the next artist wanted. (Today's equivalents are all owned by Disney, for example.) This is also how science and philosophy functioned for ages.
The worldview holding the modern copyright system to be the moral reality is the elaborate rationalization, ingrained into people by the interested parties. You can research the history of copyright law if you want.
This is a separate issue from caring about compensating and nurturing the artists, which is often what people who are mindful about this stuff do. Just not necessarily inside the "traditional" framework.
> Rather than simply admitting that there is something at least a little immoral about benefiting from someone else's work without paying for that work
But there isn't anything immoral about benefiting without paying. At least under consequentialist utilitarianism, one of the main doctrines in ethics.
And why would there be? Someone benefits but no one else loses. If someone has planted a try by the road and I relax in the shade for a few minutes, have I done anything wrong? If I admire a fine bit of architecture have I done something wrong? If I pause to watch the kids playing in the playground have I done something wrong?
> Rather than simply admitting that there is something at least a little immoral about benefiting from someone else's work without paying for that work
You've got it backwards. The onus is on you to provide a convincing argument that sharing documents without paying directly the authors is immoral.
If the document is useful and popular, then I see no immorality in sharing it without paying the author. For paper books, the readers do not pay the authors directly either, they pay the distributor the agreed price. In other cases, this agreed price is the marginal cost of file download.
Publishing books in the current model is like planting flowers in a public space, with seeds you've just taken from a bunch of other people's houses, and then requiring people who walk there or look at the flowers to pay you. I mean, we should be encouraging caring about the commons in some way. But the creators or copyright holders for cultural creations don't inherently have the power to dictate the schemes they like.