In the Second Treatise of Government, John Locke wrote:

Though the Earth, and all inferior Creatures be common to all Men, yet every Man has a Property in his own Person. This no Body has any Right to but himself. The Labour of his Body, and the Work of his Hands, we may say are properly his. 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. It being by him removed from the common state nature placed it, it hath by his labour something annexed to it, that excludes the common right of other Men. For this Labour being the unquestionable Property of the Labourer, no Man but he can have a right to what that is once joined to, at least where there is enough, and as good left in common for others.

The last part of this passage—“at least where there is enough, and as good left in common for others”—was dubbed the Lockean proviso by Robert Nozick in Anarchy, State, and Utopia (1974), and that label has stuck. Nozick delved into the implications and problems with his understanding of this proviso in considerable detail, but in my judgment Nozick’s discussion would have bewildered Locke, who would scarcely have recognized any connection between his proviso and many of Nozick’s comments. The same is true of how Nozick treated other features of Locke’s theory of property. Locke presented his justification of property briefly and in general terms, and his commentators have had a field day in drawing out and criticizing what they believe to be the implications of his theory. But some  commentators appear to be more interested in showing how clever they are rather than making a serious effort to understand Locke’s essential points.

Regarding “Locke’s proviso” that in the original acquisition of natural resources there should be “enough and as good left in common for others,” Nozick claimed that this “is meant to ensure that the situation of others is not worsened.” According to Nozick (p. 175) , “The crucial question is whether appropriation of an unowned object worsens the situation of others.”

But this isn’t what Locke said, and the Lockean proviso doesn’t require that original claims to private property in natural resources should not “worsen” the condition of anyone else. Suppose that Jack and Jill desire to cultivate the same plot of land and thereby claim exclusive ownership, but that Jack gets to that plot first and homesteads it before Jill arrives. If Jill desired that plot of land but was too late to establish title to it then she might regard her situation as “worsened” by Jack’s prior claim, but this is not what Locke had in mind in his proviso. Much of Nozick’s subsequent discussion of some implications of the “worsening” proviso therefore has little relevance to Locke’s theory. The standard that the condition of others should not be worsened by one’s appropriation of natural resources is highly subjective, whereas Locke’s proviso was reasonably objective.

Consider another one of Nozick’s objections to Locke’s theory of property.

Why does mixing one’s labor with something make one the owner of it? Perhaps because one owns one’s labor, and so one comes to own a previously unowned thing that becomes permeated with what one owns. Ownership seeps over into the rest. But why isn’t mixing what I own with what I don’t own a way of losing what I own rather than a way of gaining what I don’t? If I own a can of tomato juice and spill it in the sea so that its molecules (made radioactive, so I can check this) mingle evenly throughout the sea, do I thereby come to own the sea, or have I foolishly dissipated my tomato juice?

Nozick’s tomato juice scenario is about as sophistical as it gets, so only the briefest of replies is called for, to wit: Tomato juice is not labor, and Locke’s mixing metaphor has nothing to do with the mingling of molecules. As for the question, “But why isn’t mixing what I own with what I don’t own a way of losing what I own rather than a way of gaining what I don’t?”—this ignores Locke’s premise that labor is the only method by which one’s fundamental right of self-preservation can be exercised.  Moreover, Locke regarded labor as an inextricable part of self-ownership and hence as inalienable.

Another common objection to Locke’s labor theory of property titles has to do with what A. John Simmons called “the boundary problem” In The Lockean Theory of Rights (Princeton, 1992, p. 268), Simmons wrote:

Locke’s mixing argument also faces what we can call “the boundary problem.” It is not obvious that labor can ground a clear right to anything if it is not possible to specify the boundaries of what is acquired by labor. But exactly what does labor get mixed with when one labors on what is common? When I enclose and grow a field of corn, I seem to acquire property in the fence and the enclosed land. Yet I actually touch or work on only some of the enclosed land. The ground between the furrows and between the field and the fence seems not to have my labor mixed with it. Can others rightfully come and use (or cart away) what my labor is not mixed with?

Some reasonable, if obvious, points are raised here, but they overlook what Locke had to say about social conventions and their relationship to property rights. Locke understood that although labor establishes a legitimate moral claim to unowned property (especially land), it cannot with precision, in each and every case, determine the precise boundaries of the property so acquired. We see this in section 45 of the Second Treatise of Government. “Labour, in the Beginning, gave a Right of Property”; but it was communities that “settled the Bounds of their distinct Territories…and so, by Compact and Agreement, settled the property which Labour and Industry began.”

This may be what Locke had in mind when he stated that the moral justification of private property “does not depend on the express consent of all the Commoners” (my italics). Philosophers, then as now, typically contrasted express consent with tacit consent, and Locke did indeed leave room for tacit consent—not in establishing the moral justification of private property per se (which does not require “the assignation or consent of any body”) but in determining the precise boundaries of private property, especially land. Although Locke maintained that social agreements about the precise nature and limits of private property may be either express or tacit, the latter is the more interesting philosophically. It was a virtual truism in Locke’s day that social conventions could not have arisen without the tacit consent of most people in a society, so the very existence of a convention (or custom) was presumptive evidence of widespread consent. (This was the moral foundation of so-called customary law during the Middle Ages. It was often said that a customary law, even if unwritten, enjoyed the sanction of tacit consent by most members of the society in question, for only through widespread tacit consent could that custom, or convention, have developed in the first place.) I shall have more to say about the role of tacit consent in Locke’s political philosophy in later essays.

An example may help to illustrate the relationship between natural law and social conventions. Many modern libertarians will argue that the obligation to fulfill contracts is based on a natural-law ethics, but universal moral principles, even if they are valid, can only go so far. We may ask: Precisely what conditions must be fulfilled before a contract is legally binding? Is a written contract necessary, or should verbal agreements be enforceable? In a written contract, why are signatures usually required? Many similar questions spring to mind, and I know of no way to answer them by appealing solely to the general principles of a natural-law ethics. Such answers will depend on social conventions and legal standards that may vary from one culture to the next.

Likewise, we may ask: Even if we agree that labor constitutes the moral foundation of original private property, exactly what kind of labor is needed? Some kinds of labor are obvious, such as planting crops, but suppose I am raising sheep and need a certain amount of land to feed those sheep. May I claim as my private property all land that I deem necessary for pasturage? Or suppose I am an environmentalist who wishes to preserve the pristine beauty of an area of land. May I legitimately claim ownership of that land if I fence it off but otherwise leave it as is? Many such questions must be addressed by social conventions and legal rules. They cannot be deduced from Locke’s labor premise, and the particular conventions and standards may vary among different cultures with different traditions, many of which will have evolved spontaneously, without conscious planning but (according to the traditional view)  with the tacit consent of the people in a given society.

My point here is that, when attempting to understand Locke’s approach to property, it is misleading to contrast a natural-law justification of private property with “conventionalism.” Both elements are present in Locke’s account, but they operate at different levels. Labor is the essential element in his moral justification of private property, but social conventions and legal norms are needed to make legitimate claims of ownership (again, especially in land) precise. Although Locke did not put it this way, it is fair, I think, to say that he believed that though social conventions and legal norms cannot be strictly deduced from a labor theory of property, those conventions and norms are not arbitrary insofar as they should be consistent with a labor theory of property.

Thus the common claim of absolutists that a king owns all land in his kingdom, even if this belief had become customary and embedded in law, would not pass muster in Locke’s theory. Indeed, given that much of the Second Treatise is a rebuttal of the theory of absolute sovereignty, it is a safe guess that Locke developed his labor theory of property, at least in part, to discredit the property claims of absolute monarchs. The primary purpose of a legitimate government is to protect the property rights of individuals, according to Locke. People agree to leave a state of nature and submit to a government because they wish to render their property rights more secure than they would be in a state of nature.

Although I mentioned the Lockean proviso in my brief discussion of Nozick, I did not explain why Locke formulated this qualification, nor did I explain how Locke viewed the invention of money as effectively nullifying that proviso. There is, moreover, another kind of proviso in Locke’s theory, namely the “spoilage limitation”—another qualification that was rendered inoperative with the introduction of money. Some Lockean scholars have placed too much emphasis on these qualifications, given that they pertained only to the early stages of society, before money (gold and silver, primarily) made its appearance. Nevertheless, I shall briefly discuss these qualifications in my next essay.