But surely it is clear, given the origin, justification, and function of property rights, that they are applicable only to scarce resources. Were we in a Garden of Eden where land and other goods were infinitely abundant, there would be no scarcity and, therefore, no need for property rules; property concepts would be meaningless. The idea of conflict, and the idea of rights, would not even arise. For example, your taking my lawnmower would not really deprive me of it if I could conjure up another in the blink of an eye. Lawnmower-taking in these circumstances would not be “theft.” Property rights are not applicable to things of infinite abundance, because there cannot be conflict over such things.
Like the magically-reproducible lawnmower, ideas are not scarce. If I invent a technique for harvesting cotton, your harvesting cotton in this way would not take away the technique from me. I still have my technique (as well as my cotton). Your use does not exclude my use; we could both use my technique to harvest cotton. There is no economic scarcity, and no possibility of conflict over the use of a scarce resource. Thus, there is no need for exclusivity.
Ideas, unlike objects, are infinite -- my use of your idea (song, invention, formula) does not conflict with your use of your idea. That's really all you need to understand why you can't say you "own" an idea -- why "ownership" of ideas is an oxymoron that simply does not make sense.
This quotation, and select others, are there for you in the fantastic short book called Against Intellectual Property.