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What is it about tangible goods that makes them sub­jects for property rights? Why are tangible goods property? A little reflection will show that it is these goods’ scarcity—the fact that there can be conflict over these goods by multiple human actors. The very possibility of conflict over a resource renders it scarce, giving rise to the need for ethical rules to govern its use. Thus, the fundamental social and ethical function of property rights is to prevent interpersonal conflict over scarce resources. As Hoppe notes:

[O]nly because scarcity exists is there even a problem of formulating moral laws; insofar as goods are superabun­dant (“free” goods), no conflict over the use of goods is possible and no action-coordination is needed. Hence, it follows that any ethic, correctly conceived, must be for­mulated as a theory of property, i.e., a theory of the as ­signment of rights of exclusive control over scarce means. Because only then does it become possible to avoid oth­erwise inescapable and unresolvable conflict.

[...] Nature, then, contains things that are economically scarce. My use of such a thing conflicts with (excludes) your use of it, and vice­ versa. The function of property rights is to prevent interpersonal con­flict over scarce resources, by allocating exclusive ownership of re­sources to specified individuals (owners). [...] Ideas are not naturally scarce. However, by recognizing a right in an ideal object, one creates scarcity where none existed before.

Kinsella - Against Intellectual Property [pdf do artigo]