Robert E. Filman has published (in Internet Computing) a brief and very readable overview of laws involving patents, copyright, trademarks, trade secrets, and other "intellectual property," and how they got to be the way they are.
The critical thing to keep in mind about this issue is that IP is a social fiction. (Property is itself a social fiction, but that's another column.) The Schiavo case was about life and death (and the nature of both), and whether or not you believe in posting the Decalogue in every courtroom, there is considerable ethical unanimity that (with varying exceptions) killing people is a bad idea. However, while the commandments prohibited stealing, the text is more cleanly understood as prohibiting the theft of physical property, such as asses and wives, than more abstract things, like copyrights and patents.
The notion of IP is one that has evolved, as opposed to being obvious. For example, society doesn't recognize every intellectual invention as worthy of legal ownership -- you can invent a scrumptious recipe, and I can freely cook the same dish. Similarly, we don't accord ownership of IP the same unequivocal status as physical property: If you buy a physical book, you and the closure of your inheritors own that book into the indefinite future, but if you've written anything besides Peter Pan, you and your inheritors will eventually lose your ownership.