I’ve argued in the past that John Locke’s classical liberalism can be used to justify slavery and serfdom and the expropriation of indigenous nations. This reading aligns with Locke’s own role in Britain’s slave trading and colonial activities. But it leaves open the possibility that we might separate Locke’s theory of property from the philosopher’s own moral failings.

But after setting aside Locke’s less savory characteristics, we still have to contend with Locke’s claim that property can be justly acquired through labor. The crucial element — what’s called the Lockean proviso — holds that one person’s acquisition of property should leave “enough and as good” for everyone else.

In the European context, where every inch of land had been occupied since time immemorial, this was obviously a theoretical fiction. North America, however, seemed different.

The Jeffersonian Democrats made a serious attempt to practically implement Locke’s theory. Jefferson envisioned a smallholder democracy in which the land belonged to those who actually worked it rather than the European aristocrats whose property rights derived from a mythical original acquisition.

Also, the small parcels of land required to support a family farm, when compared with the vastness of North America, made the Lockean proviso look plausible. The Louisiana Purchase, which Jefferson believed would provide “room enough for our descendants to the thousandth and thousandth generation,” tested this theory.

Jefferson’s personal status as an oppressive slaveholder and his retreat from his early antislavery position don’t bear on the validity of Locke’s proviso. A Jeffersonian policy of small landholding would have been possible, and indeed arguably more viable, even without slavery and the inequality it produced among whites.

Furthermore, in considering the Louisiana Purchase, we may disregard — as did Jefferson and the American state as a whole — the fact that the land purchased from the French state came from a recent, and still incomplete, expropriation of the indigenous inhabitants.

What really matters for our analysis is Jefferson’s belief that the purchase would meet the needs of the expanding (white) American population for “the thousandth and thousandth generation.”

If that were true, then Locke’s theory would indeed describe the conditions actually prevailing in the United States. The state could implement a policy by which any citizen could attain economic independence by mixing their labor with as much land as they were able to till or graze, leaving “enough and as good” for everyone else.

In reality, however, far from enduring for a thousand generations, the Lockean proviso did not survive even one.

In the slaveholding South, this was a foregone conclusion. After the Atlantic slave trade was outlawed, “slave breeding” became the most profitable sector of the established slave states’ economy.

Slaveholders either expanded onto the newly acquired land or shipped their slaves to the growing market, often breaking up families in the process. These wealthy landowners left little for the Jeffersonian yeoman class, who settled on infertile or mountainous land unsuitable for cotton and other slave crops.

But even where slavery was excluded by the Compromise of 1820, the contradictions inherent in the Locke-Jefferson theory rapidly revealed themselves. By the 1820s, the new nation was already pressing against the boundaries of Jefferson’s expansion. Settlers from the United States began arriving in the (then) Mexican province of Texas, reaching such numbers that the Mexican government banned further immigration in 1830. In 1834, barely thirty years after the Louisiana Purchase, the Texan revolution began, leading to the annexation of Texas by the United States in 1845.

By the time of the Compromise of 1850 the nation ran “from sea to shining sea,” having grabbed the Southwest from Mexico, Oregon and Washington from Canada, and everything in between from the indigenous inhabitants.

Advocates of Manifest Destiny proclaimed — and piratical adventurers called “filibusteros” sought to forcefully implement — an empire extending over all the Americas. The failure of the Lockean proviso directly led to the Civil War, as slaveowners and Free Soilers fought over “bleeding Kansas.”

Almost as soon as the Native American population was expelled or wiped out, the land was converted to private property. The inexhaustible flow of pioneers pushed the frontier further and further. By the 1870s, the wars of colonization and expropriation were replaced with a string of small battles between rival groups of ranchers and farmers. Victory typically went to whichever side did a better job enlisting or co-opting state power.

We find the same history repeated, with minor variations, in Australia, southern Africa, and throughout the New World. Europeans filled vast areas — which, under the Lockean doctrine of “mixing labor with the soil,” could be regarded as unused by their native inhabitants — within years, then began struggling among themselves for the right to occupy the land.

As this sorry history shows, Locke’s proviso is fundamentally at variance with the core doctrine of classical and neoclassical economics, that human needs and desires are unlimited while resources are invariably scarce. The idea of founding a defense of capitalism on a Lockean doctrine of just acquisition of property is inherently contradictory, pitting the role of the market in managing scarcity against a hypothetical origin story in which the absence of scarcity is critical.

Today, wealth is no longer derived from the ownership of agricultural land, however that land might have been originally acquired. This limits the usefulness of any Lockean theory of just acquisition for modern propertarians.

That said, it opens another possibility: even if Locke’s theory was false when he proclaimed it, the development of the modern capitalist economy — where property is acquired through competition and innovation, a process that may be seen as satisfying the Lockean proviso — posthumously validates it.

But this claim fails for a number of reasons. First, though most large fortunes don’t depend on agriculture, control of natural resources remains important. Some of the world’s largest companies (most notably ExxonMobil) and richest families (like the Kochs and Gettys) were built on oil profits. And, as the long history of struggle over the control of oil resources has shown, the Lockean proviso does not apply here.

Even more important, however, is the central role intellectual property — the core of the value of companies like Apple and Google — plays in the modern economy. Ideas, in a state of nature, exemplify a pure public good, and therefore the Lockean proviso.

In the absence of coercion, anyone can make use of an idea, while leaving “enough and as good” for everyone else. But patents, copyrights, trademarks, and other ways of asserting intellectual property prevent this.

More fundamentally still, Locke’s idea of appropriation only makes sense if we believe that individual effort can generate wealth. This was at least superficially plausible for Jefferson’s yeoman farmers, who worked a small plot of land with only the aid of animals and some simple tools and supplied most of their own needs, including food and clothing.

That their agricultural technology was the product of millennia of human development and that their self-sufficiency was ultimately underpinned by access to a market economy could be ignored most of the time.

In a modern economy, however, interdependence reveals itself immediately. No one can acquire any kind of income or property without countless other people’s assistance. Propertarians are outraged when this is pointed out to them as evidence against Lockean ideas of natural rights to property, as when even Barack Obama observed, “You didn’t build that.”

In my previous essays, I pointed out the historical role of Locke’s theory of property played in expropriation and enslavement. The case is no better for contemporary propertarians like Robert Nozick and Murray Rothbard. By reviving the proviso in a slightly weakened form, Nozick seeks to provide a theoretical justification that allows some property holders to expropriate others by breaking the legal and fiscal obligations under which those rights were acquired.

Rothbard disclaims the proviso but effectively revives it with the Jeffersonian notion of “homesteading” which implicitly assumes the acquisition of a small plot of land, rather than the fencing off of a vast estate. The reality of the race to grab as much land as possible the moment it becomes available (usually through dispossession of the previous inhabitants) seems to have passed him by.

Underlying all of this is the Lockean proviso’s nonsense that it is possible to fence off some part of the world — whether the physical world or the world of ideas — while leaving “enough and as good” for everyone else.

If we reject this doctrine, where does that leave actually existing property rights? The answer is that property rights, like legally enforceable rights in general, are social institutions that may or not be consistent with concepts of justice and human rights.

Our long experience of capitalism suggests that the unfettered exercise of property rights — and polices that allow massive accumulations of wealth in the hands of a few — lead to inequality, crisis, and ultimate disaster.