To "own" a thing means simply that you get to decide how that thing is used which is to say how, where, and when its potentials are applied. In principle, any concept which can serve as a noun in language can be owned, provided you can establish a chain of physical command from your decisions all the way down to the applications of the thing's potentials.

E.g., you "own" your hand because your brain controls nerves which control muscles which control your hand. You "own" your house because your hands control a pen which controls bureaucrats who control the police who restrain other physical entities that might try to apply your house's potential. If you are in prison or the military, there is a degree to which you no longer own your body any more since external forces can overpower that nerve/muscle chain.

Don't confuse actual ownership with the "right" of ownership. The latter is, of course, what is useful to debate about -- whether one "should" own this or that. When the right to own is agreed upon and set into law, then the pen is in control and ownership is, to one degree or another, conferred.

There is nothing metaphysical about the right of ownership -- it is something we must decide in order to best satisfy our goals, which here presumably are rational egoism. "Thou shalt not kill except in self defense" is an example of such a decision -- it is one of the agreements that relatively firmly establishes each person's ownership of their own body. But again, there is nothing that philosophically necessitates this agreement -- a human can certainly exist as property; we call them a slave. Whether slavery is or is not in favor of our rational egoist goals is a pragmatic debate, in effect, not a metaphysical one.

This straightforward view of ownership adds a little clarity to some usually murky applications such as Intellectual Property ("IP"), or Market Protectionism (legal monopolies). If someone invests the time and money into developing an idea, can/should they "own" that idea? If someone invests the time and money to spawn a new market, can/should they "own" that market?

Can markets be owned? Yes: "the market" -- there, it passes my litmus test. Companies are granted ownership of markets all the time -- pick your favorite legal monopoly, such as perhaps your local cable service. There is nothing metaphysically different about market ownership than hand ownership -- it's just that the chain of command is much more abstract in the former case. (Actually, as I pointed out even the chain of command allowing you control of your hand includes the bureaucratic hierarchy that ultimately prevents other from deciding what to do with it, so the two examples are not even so different on the score of abstraction.)

Should markets be owned? That is, is it in our rational self interest to promote a system that enforces ownership over markets? It has advantages and disadvantages, which interestingly are essentially the same advantages and disadvantages as promoting the ownership of ideas or methods (IP). Advantage: people/companies are (supposedly) more likely to invest significant capital up front to develop said markets/methods because once developed they will reap greater rewards ("recover their investment"). Disadvantage: other people/companies being barred from utilizing the same markets/methods means a lack of both competitive pricing and competitive application of the potential of the markets/methods. I.e., in all senses, the potential of the markets/methods falls into suboptimal use.

So both answers seem to inhibit progress and efficiency in one way or another, which means they need to be weighed against each other, and one may be distinctly better than the other, or there may be some optimal balance.

My personal analysis might go something like this: Protectionism may foster the development of new resources, but this is just a shifting of investment from one domain into another and hence not inherently a creation of wealth. Lack of protectionism, on the other hand, allows optimal utilization of what already exists, which means strong productivity from a very broad base, and thus, I suspect, much greater creation of wealth. The drive to innovate is there as a necessity to contain and control this greater wealth, and hence I believe progress would in the end be both faster and more robust in the absence of all protectionism.

But this begs the question: when do we start calling ownership "protectionism"? One possible way to look at it is this: For any given "thing", does it become more or less productive on the whole as it is utilized by more entities? Many things--like your body, or physical land--suffer the tragedy of the commons at some point, and these, perhaps, are the things which should be "owned". Other things simply produce diminishing returns, which means they're ripe for open competition. And still others never stop producing, which means the more who use it, the merrier. By these criterion, I would say that "IP" constitutes protectionism and we are better off without it.