[I typed this up as a reply to a comment that has now been flagged. I think it's a conversation worth having, so I'm putting it at the top level instead.] I'd argue that "intellectual property" is fundamentally different from physical property, and can't really be "stolen" per se. If I steal your car, I have a car and you don't have a car. If I "steal" your book, we both have the book. I'm better off, and you're no w…
I think another analogy can be better. Imagine I want to fly somewhere, plane is half empty, I am going there and sitting. Don’t have ticket. (Imagining no enforcement) Should I? Eventually this plane will fly there, my effect on cost is ignorable, I will be better, airline will not be worse.
However marginal cost is not zero for the airline. Fuel costs money. There are limited seats on the plane. The marginal cost of copying a digital book is actually zero.
However, even if marginal cost was 0 (lets say a movie theatre that is empty), it does somehow still seem wrong if its physical in a way i can't easily distinguish from the digital case.
I suppose maybe the difference is, that if i own a piece of land, i should have the right to prevent trespassing so i can enjoy the land without being harrased. Being able to charge admission is an extension of that. But the intellectual case, someone reading my book doesnt prevent me from enjoying reading my book myself.