Many people argue that individuals are endowed with certain natural rights. Those of a libertarian persuasion often claim that individuals have a natural right to the property they own. Comparatively, those of a progressive disposition often assert that individuals have a natural right to particular goods such as a minimum level of income. In this post I want to focus on the libertarian argument. In particular, I would like to claim that it is largely unpersuasive. (There are obviously numerous criticisms of the argument out there already, so I can't rule out that nothing in this post is original.)
As those who have advanced arguments for natural rights to property admit, any such argument is inevitably predicated on a theory of initial acquisition. Individuals do not come into the world with a universally acknowledged claim to a particular collection of property encoded in their DNA. Any property that is not purchased or inherited must be acquired somehow. The most commonly cited theory of initial acquisition, which owes its origin to John Locke, is the so-called labour theory. (If anyone knows a better theory, I would genuinely be interested to hear about it.) In The Second Treatise on Government, Locke asserts, "Whatsoever then he removes out of the state that nature hath provided, and left it in, he hath mixed his labour with, and joined to it something that is his own, and thereby makes it his property." The claim is that a person who improves some resource by mixing his labour with it thereby acquires a natural right to the resource.
The main problem with Locke's theory, in my opinion, is that it is wholly arbitrary. To begin with, it does not specify how much labour a person must undertake before he may acquire a natural right to a particular resource. If someone chops down ten trees and builds a log cabin, has he acquired a natural right to the cabin? What if he chops down the trees and starts building the cabin, but does not finish it? What if he just chops down the trees? What if simply touches one tree with the blade of his saw? Suppose a person arrives at a hitherto unclaimed forest, and makes a tiny incision in every single tree. Does this give him a natural right to all of those trees? Suppose a person goes fishing in an otherwise deserted stream every day for two months. Does this give her a natural right to the entire stream along with its constituents?
Locke's theory is arbitrary not only with respect to the quantity of labour necessary for acquisition, but also with respect to the extent of acquisition. If someone acquires a natural right to a certain piece of land by mixing her labour with it, does she then also acquire a natural right to a column of air going infinitely far above the land and a column of crust going downward toward the centre of the earth? Similarly, if smoke from someone else's factory blows into the air immediately above her land, has her natural right to the land then been violated? What if the smoke blows into the air ten feet above her land? What if it blows into the air one hundred feet above her land?
As far as I can see, there is no non-arbitrary way to conceptualise the initial acquisition of property. Consequently, it does not seem possible to meaningfully claim that individuals have a natural right to property they have acquired. And since all property must at some point have been acquired, it does not seem possible to meaningfully claim that individuals have a natural right to property they have purchased or inherited either.