There was a time when the word “liberal” meant something closer to what we currently mean when we say “libertarian.” This should not be surprising, since the root word of both is “liberty.” Unfortunately, the definition of “liberal” has drifted—and various liberal ideals have drifted along with it.

Take rights, for example. Liberals from John Locke to Thomas Jefferson have always been known for their advocacy for people’s rights. In their time, the word “rights” referred to things that it is wrong to forcibly prevent someone from doing. Nowadays, the word often refers instead to anything the speaker wants the government to provide.

To see this change clearly, consider the U.S. Constitution’s “right to bear arms.” It was never taken to mean that the government should buy you a gun. It meant that neither the government nor anyone else is justified in forcibly stopping you from peacefully acquiring one. Compare this to modern advocacy for “the right to healthcare.” This is commonly taken to mean that the government must provide people with healthcare, and is justified in forcibly taxing non-consenting citizens to do so. Because of this shift, many people today describe themselves as “liberals” while advocating for illiberal ideas like government controlled healthcare, secure in the belief that they are simply standing up for people’s rights—just like Jefferson and Locke!

To the average American, “liberal” now means what “progressive” or “socialist” once meant. Ironic, since those groups were always among the primary enemies of liberalism. It is not clear whether this was a deliberate infiltration and corruption of the movement, or simply an accident of linguistic evolution. Do modern liberals not know that they are using the word “rights” differently from Jefferson and Locke, or do they just not care? Either way, it is clear that the change has heavily hampered those in favor of liberty. Classical liberals spent a long time developing a good name for themselves, only to have it stolen by their enemies—intentionally or not.

The liberal movement had to rebrand itself as “libertarian.” Or, perhaps the true, hardcore liberals created an offshoot movement known as “libertarianism” when the original movement died out. It is hard to say whether it is still the same movement after a generation of development and a name change—it’s a Ship of Theseus problem, compounded by the Athenians renaming the ship. But if the ship of liberalism can still be said to exist, its bow now reads Libertarian.

There is a danger that our new label may succumb to the same fate as the old one. Language changes. Any other words we use to establish clearly what we mean by “libertarian” can simply be twisted by the unscrupulous or ignorant to use our label while rejecting our philosophy.

To see how this might happen, let us look at some definitions provided by important libertarian figures, and see if we can corrupt them. Many consider Murray Rothbard to be the quintessential libertarian, so we shall start with him.

“The libertarian creed rests upon one central axiom: that no man or group of men may aggress against the person or property of anyone else. This may be called the “nonaggression axiom.” “Aggression” is defined as the initiation of the use or threat of physical violence against the person or property of anyone else.”

-Murray Rothbard, For a New Liberty

This is trivial to corrupt. I could claim that trespassing on your property is not violence, but forcibly ejecting me from your property is. Therefore, defending your property from trespassers is against libertarian values. I would, of course, need to ignore what Rothbard would say about this interpretation, just as modern “liberals” ignore Locke. It would be a perversion of the original meaning of the author, but if libertarianism becomes successful, there will be significant incentive to pervert it. Many will want to use the label for social or political reasons while rejecting—or even violating—libertarian ideals. Once the incentive to pervert our language has had enough time to do what incentives do, the definitions of “physical violence” and “aggression” will change, and it will no longer seem like a perversion.

In the libertarian sphere, Rothbard’s opposite is probably David Friedman—a dichotomy which Rothbard himself endorsed in his essay “Do You Hate The State?” By quoting both, we will hopefully cover as broad a range of libertarian views as is possible with two examples.

“The central idea of libertarianism is that people should be permitted to run their own lives as they wish. We totally reject the idea that people must be forcibly protected from themselves.”

-David Friedman, The Machinery of Freedom

This, too, is easily corruptible. There are multiple ways of interpreting “permitted.” I could say that by publicly criticizing your choices, I am applying social pressure, thus not permitting you to make them. Therefore, libertarians oppose criticism of personal choices. Again, it is obvious to us that this is a distortion of the author’s intent. Again, it will not be so obvious after a little linguistic drift.

Tackling this problem may seem hopeless, but fortunately it has already been solved by the Global Positioning System (GPS).

A single GPS satellite does not know where your phone is, only how far away it is relative to the satellite. This narrows down your location to somewhere on the border of an imaginary sphere surrounding the satellite. Because we can assume you are on the surface of the Earth, this sphere’s intersection with the Earth forms a circle of possible locations. It takes two more satellites to pinpoint your location accurately enough to be useful. The second satellite narrows it down to two points—where those two circles intersect—and the third narrows it down to one of those two intersections. This is often called “triangulation,” but apparently that is a misnomer, and it should be referred to as “trilateration.”

This is, of course, a huge oversimplification of how GPS works, but the principle is what is important: When you have information on something’s proximity to a certain point, you can narrow its location down further by considering its proximity to additional points.

By analogy, it is possible that we can reduce the uncertainty in the definition of libertarianism by defining it not just once, but three times, all while making it clear that all three definitions amount to the same thing. It is easy to shift the meaning of one definition. It is much harder to shift the meaning of three different yet synonymous definitions while maintaining synonymy.

With all that out of the way, here are three ways of defining libertarianism, all of which are not obviously synonymous unless you understand them in the way that current libertarians do:

1. A libertarian is someone who advocates for liberty.

Liberty is the right to freely act without being interfered with by others, so long as you do not interfere with the ability of others to do the same.

2. A libertarian is someone who advocates for private property rights.

Private property rights mean that control of things is allocated to individuals. I control my property, you control yours.

3. A libertarian is someone who advocates for voluntary interaction.

An interaction which is voluntary is one to which all parties involved consent.

Read definition one again, and consider this: If liberty only covers actions which do not prevent others from exercising their own liberty, what do we make of the mutual exclusivity of action? When I drink a beer, you can no longer drink it. When I play a guitar, you can not play it at the same time in the same way. When I do anything, I prevent you from doing something. Does a commitment to liberty require that we never do anything, lest we impede the liberty of others? In fact, even doing nothing would fail to solve the problem, because by standing still, I am preventing you from standing in the same spot!

This is why the concept of liberty is useless without some concept of property. Once we define liberty within the bounds of property rights, then whether you are violating my right to drink that beer when you drink it yourself depends on whose beer it is. If it is your beer, then you are not violating my right to drink it; because I have no such right. However, if I drink your beer without your permission then I am violating your right to drink it; because you do have such a right. In definition one, being “interfered with by others” means having your property rights violated.

Furthermore, property rights are inherently individualistic (or private) because if two people are said to both own the same thing, then it has not been established who takes precedence when they both want to use it for mutually exclusive purposes. Whatever you use to establish who does have the right to use it is your true concept of property.

That is how definitions one and two are the same. Saying that private property rights must be upheld is the same as saying that people must have liberty. Both mean that we have the right to do what we will with what is ours.

This is also the same as saying that all interaction should be voluntary. As per definition three, an interaction which is voluntary is an interaction in which everyone involved consents. In this context, “everyone involved” means the owners of the property involved. When I take a taxi ride, this involves three property owners: I own my body and my money, the taxi driver owns his body, and the taxi company owns the car (we’ll ignore the road for now; I don’t want to trigger my libertarian readership). If all three of us consent then the interaction is voluntary by a libertarian definition. A rival taxi driver might not consent, but that does not matter, because he does not own any of the property involved. If we did not make this distinction, then the only interactions which would be classed as voluntary would be interactions with which everyone in the world agreed. Thus, libertarians understand that to have any usefulness, voluntary interaction must be defined by individuals exercising their liberty with respect to their own private property.

Some may try to claim that by their definition, our taxi hypothetical is not really voluntary. A socialist, for example, might say that the taxi driver will starve if he does not do the job, and that for an action to be truly voluntary it cannot be a decision made under such conditions. Therefore, the socialist argues, the hypothetical transaction is anti-libertarian. He may then even argue that, by extension, all of capitalism is anti-libertarian as well. Capitalism is simply libertarianism applied to capital goods, so a corruption of our definitions which classifies capitalism as anti-libertarian is a dire corruption indeed. How does our trilateration approach deal with it?

First of all, it is ridiculous to posit starvation under capitalism. If someone actually starved to death due to poverty in even a relatively capitalist country, this would be big news. We do not see such news, indicating that it simply does not happen. But we will put that to one side. The important point here is that even if he would starve, the interaction remains voluntary.

Perhaps the socialist definition of “voluntary” requires that nobody will starve if they do not participate, but the libertarian definition does not. This is not to say that we are indifferent to people starving, only that it is not part of our definition of voluntary. To libertarians, voluntary interaction is just another way of looking at liberty or private property. My money is not the taxi driver’s private property, therefore it is not a violation of his liberty to withhold it until he performs the job, and therefore the interaction is voluntary.

For another example, consider a Republican arguing that eminent domain is consistent with libertarian values, because once the government declares ownership of some land, it is the legitimate property of said government. Furthermore, argues the Republican, the previous owner was compensated for the land, thus the government acquired that property in a legitimate exchange. This is certainly a concept of property, but it is clearly not the libertarian concept of property. A legitimate transfer of private property is determined not by compensation, but by voluntary interaction. It does not matter what you give someone in exchange for taking his property. If he does not voluntarily agree to relinquish it, then the property still belongs to him, and he has the liberty to refuse the offer. Again, all it takes to understand that the Republican is misrepresenting libertarian values is the premise that advocacy for private property is synonymous with advocacy for liberty and voluntary interaction.

This is not the same as the current strategy of simply referring to a definition provided by an important libertarian figure to expose the misrepresentation of a word—the words in that definition can always just be misrepresented as well. Instead, we are referring to three definitions (or a single definition with three parts) all of which are declared to be synonymous, and which thereby mutually hold one another in check.

It is possible to imagine the definition of “private property” drifting to include anything the government declares ownership of, the definition of “voluntary interaction” drifting to require interactions to include alternatives which are sufficiently desirable, and the definition of “liberty” drifting to require people to be free of any social pressure. But once these drifts happen, our three definitions of libertarianism are no longer synonymous.

You may be able to misrepresent the locations of the GPS satellites to some degree, but the further you misrepresent them, the greater the chance that the circles of possible coordinates will no longer intersect, exposing the misrepresentation.

This defense is not perfect. If you’re looking for a flawless method of using words to pin down other words, you’ll be searching until the end of time. Mere words can not replace the need for eternal vigilance by those within the movement. But that is different from saying that good definitions do not help at all. So if you want a definition of libertarianism that is less susceptible to corruption, try this one: A libertarian is someone who advocates for liberty, private property, and voluntary interaction, and sees all three as fundamentally the same thing.