If you were to catalog all the ways people use the words “freedom” or “liberty”, you’d probably come up with a pretty long list. (Here’s an experiment: Search your iTunes library for songs with the word “free” in their title, and then explain what the word means in each of those songs.) At least at first glance, it would seem people don’t use the words in any univocal way.

When philosophers start to analyze the concept of “liberty”, they need to start by looking at actual use. We’re talking about a word with a history. "Liberty" is a concept philosophers are interested in, but it's a not a philosopher's technical term.

Here is a partial list of the ways that people use the terms “freedom” and “liberty”. Call the different items on this list different conceptions of freedom.

1. Freedom as Absence of Obstacles: Someone is free to the extent that no obstacles impede her ability to do as she pleases.
   1. Freedom as Absence of Interference: Someone is free to the extent that no one interferes with her ability to do as she pleases.
   2. Freedom as Absence of Deliberate Interference: Someone is free to the extent that no one deliberately interferes with her ability to do as she pleases.
   3. Freedom as Absence of Wrongful Interference: Someone is free to the extent that no one wrongfully interferes with her ability to do as she pleases.
2. Freedom as Capacity: Someone is free to the extent that she has the power, ability, capacity, or means to do as she pleases.
3. Freedom as Autonomous Self–Control: Someone is free to the extent that she exhibits sufficient deliberative self-control, such that she is authentically the author of her actions.
4. Freedom as Non-Domination: A person is free to the extent she is not subject to another person’s or group’s arbitrary will.
5. Freedom as Moral Virtue: A person is free to the extent she has the power to recognize and act upon her moral obligations.
6. Freedom as Absence of Pressure: A person is free to the extent she feels no social pressure to do anything.
7. Freedom as Absence of Reasons: A person is free to the extent she has no grounds or reasons for making decisions.

And so on. Notice that 1a­–1c are just more specific version of 1.

At first glance, the words “freedom” and “liberty” refer to a plurality of related but not identical things, which bear a kind of family resemblance to each other. Perhaps we can come up with a general theory of liberty that unites all these conceptions under one definition. (See work by Gerald MacCullum and Ian Carter on this point.) Or, it might just be that we’re stuck with pluralism.

Most of the right libertarians I’ve met are hardcore revisionists (about the English language) when it comes to freedom. Most of them think the only valid conceptions of liberty are 1b or 1c above. They think other uses are confused, ideological, or demonstrably wrong. Over the next few days, I’ll explain and undermine some of their reasons for this. I’ll also make the case for why classical liberals should embrace positive liberty (freedom as capacity). Some classical liberals and libertarians tend to think that if you admit that positive liberty is a form of liberty, and if you claim that institutions should promote positive liberty, then you've got to reject market societies in favor of socialism. That seems to me to be a big mistake.