by Robert Gressis
Libertarians, like Robert Nozick, care most of all about negative freedom, i.e., freedom from interference. If you have little money, but the appropriate agency protects you from force and fraud, then you have negative freedom, even if you find yourself unable to do much of what you want to do. Consequently, since a large state has to be funded by taxes, and since taxes require interfering with people (“give us some of the money you earned, or else we’ll fine you and possibly put you in jail”), libertarians advocate for as small a state as they think we can have while still functioning as a society.
In the USA, we call people “libertarians” if they think that the fundamental role of the state is to protect people’s liberty, and if they also think that “liberty” consists in negative freedom. But this is not the only kind of libertarian there is: you can be a libertarian who thinks that the fundamental role of the state is to protect people’s liberty while also construing “liberty” as positive freedom, by which is meant the freedom to do what you want. Call such people “left-libertarians.”  It is precisely because they care about freedom — positive freedom — that they advocate for a much larger state, one that secures the material conditions people need to be able to pursue their goals. Because I want to begin this essay by contrasting the libertarians who care most about negative freedom with those who care most about positive freedom, I will call the negative freedom libertarians “right-libertarians” and the positive freedom ones “left-libertarians.”
Now, it’s not that right- and left-libertarians don’t care about the other kind of freedom (though some really don’t). Rather, they tend to think one kind of freedom is much more important than the other, at least for purposes of political philosophy. If you tell a left-libertarian, “Hey, your preferred government violates people’s freedom because it takes away a lot of their money that they worked hard to make, by taxing them to fund public schools, universal healthcare, free college, etc.,” the left-libertarian will give one of three responses:
Compromiser: “It violates their negative freedom a bit, but when the average person has greater positive freedom, he ends up having greater negative freedom as well.”
Opposer: “Yes, it violates their negative freedom, but in doing so it enhances positive freedom to a much greater degree, and positive freedom is more important than negative freedom anyway.”
Denier: “It doesn’t violate their freedom at all because that money wasn’t justly theirs anyway.”
The Compromiser argues that a left-libertarian regime gives us the best of both worlds. Indeed, even right-libertarians should be happy with it, because a left-libertarian regime gives us not just positive freedom but enough negative freedom to satisfy right-libertarians too. The Opposer admits that right-libertarians are unlikely to be happy with a left-libertarian regime, but says that they’re weighting things in the wrong way, so it’s OK if right-libertarians don’t get what they want. And finally, the Denier doesn’t even distinguish between positive and negative freedom. She has already concluded that positive freedom is the only real kind of freedom there is and may even think that right-libertarians are not libertarians at all. She may even call them “propertarians,” to indicate that they only care about property, not freedom.
Similarly, if you tell a right-libertarian, “Hey, in your perfect society the government violates people’s freedom because it doesn’t give them what they are owed, and what they need to do what they want”, the right-libertarian response can be divided into the same three categories:
Compromiser: “It only violates some people’s positive freedom, because in letting people pursue their own ends, the modal person enjoys much greater positive freedom than he would under a socialist government”;
Opposer: “Yes, it does violate their positive freedom, but it enhances their negative freedom to a much greater degree, which is more important anyway”;
Denier: “It doesn’t violate their freedom, because the government doesn’t owe people anything other than protecting them from force and fraud.”
Again, notice the Denier doesn’t even distinguish between positive and negative freedom. He has already concluded that negative freedom is the only kind of freedom there is.
I bring up these well-worn points, because there seems to me to be a similar distinction going on when it comes to diversity, and yet I don’t see these points made when people discuss the subject. (Perhaps, I haven’t been looking hard enough). For example, conservatives (and Marxists, and liberals; but I’ll just call them conservatives, because in an American context they’re trying to conserve norms that were regnant as late as 2010) will often say that progressives don’t truly care about diversity, because they never seem to be concerned about ideological diversity (which the conservative usually thinks of as the most important kind of diversity), and I often hear progressives simply equate diversity with just identity diversity: diversity among kinds of identity, such as racial, sexual, gender, disability, and other such differences.
In other words, the diversity debate is a debate between Opposer conservatives and Denier progressives. As such, the Opposer conservatives are really wasting their time in arguing the way they are, because the Deniers don’t see ideological diversity as a kind of diversity at all.
For the Denier, intellectual diversity is not diversity at all, for two reasons. First, it literally undercuts identity diversity. This is because the Denier generally has the following views: (a) we need to increase our identity diversity; (b) the best way of doing that is to have an inclusive environment; and (c) an “inclusive environment” is one where certain kinds of things are not said and there is a lot of identity diversity. 
But a certain kind of ideological diversity makes (c) much more difficult, if not impossible. In particular, people who question (a), (b), and (c). If you have conservatives around who feel comfortable questioning (a) – (c) – well, then, it is important that you don’t have any conservatives around! Indeed, it’s a prediction of the Denier’s theory that the more of this kind of ideological diversity you have, the less identity diversity (of the right sort) you will have. 
The second reason the Denier progressive doesn’t think of intellectual diversity as a kind of diversity is that when it comes to (a) – (c), the Denier thinks there is no reasonable debate to be had. Wanting to have a reasonable debate about (a) – (c) is like wanting to have a reasonable debate about whether women should have the right to vote or whether the United States should reinstitute slavery, etc. It’s pointless to have a debate about these things, because either the right answer is clear to you or you’re a deeply suspicious person. You’re either arguing these things for fun, not truth – in which case, go have fun somewhere else – or you want these things, in which case get the hell out of here.
Now, I’m overstating things a bit. Presumably, the Denier does care about ideological diversity to some degree. It’s just, the kind of ideological diversity the Denier doesn’t care about is the kind of ideological diversity the conservative does care about. So, when the conservative says, “you claim to care about diversity, but you don’t want conservative ideas around!” this is like saying to the right libertarian, “You claim to care about freedom, yet you don’t want a huge welfare state!” Anyone who says this really doesn’t get the debate they’re in.
It’s also worth noting that the progressive can attempt a tu quoque on the conservative. The progressive can say, “Why do you care about ideological diversity anyway?” At this point, the conservative will probably invoke Mill: (d) we don’t know what the truth is, so (e) it’s important to have lots of different takes on the issue, to increase our chances of finding the truth, and (f) even if we think we do know the truth, it’s important to have people around who question it, so that we can come up with the best arguments for it.
But then, the progressive can say, “Do you want lots of people around who question (d) – (f)?” Here we get to the paradox of intolerance. The conservative will either say, (i) “yes! I do!” or (ii) “well … no, I don’t.”
Imagine the conservative says (i). If he’s a student of the recent present, he’ll see what happens when you have lots of people around who question (d) – (f). You get progressive control of university departments and many administrative agencies, for the simple reason that the conservative won’t hold someone’s views against (or for) them when he’s trying to hire someone new, whereas the progressive will. Consequently, the more progressives you get, the more progressives you get.
But if he says (ii), the progressive can say, “You’re just like me! I think there are certain non-negotiables – (a) -(c) – and you think there are certain non-negotiables, too, namely (d) – (f). We just differ over what is non-negotiable.”
It’s no wonder, then, that Richard Hanania, a conservative, has come out and said that diversity doesn’t matter. In Hanania’s view, the reason diversity doesn’t matter is that what we’re interested in is finding the truth, so, he accepts (d) above. Consequently, we should value whatever it is that allows us to find the truth. If diversity — of any kind — does that, then great, let’s get diversity. But if doesn’t, who cares?
But Hanania thinks diversity doesn’t help us find the truth (he denies (e) above). Rather, since there are many ways to be wrong but few ways to be right, increasing ideological diversity will just increase the ways in which you’re wrong. E.g., getting a bunch of flat-earthers in biology departments will increase ideological diversity, but it will reduce your chances of finding the truth, because flat-earthers are wrong.
So, what does help us find the truth? He thinks that there are at least two things we know of that do help us find the truth: intelligence (which he equates, rightly or wrongly, with high IQ) and good intellectual hygiene (being willing to engage in cost-benefit analysis thinking, caring about evidence, being open to being wrong, and being willing to revise your thinking in light of the evidence). If you’re interested in finding the truth, you should hire people who have those features.
So, what can the Millian who thinks ideological diversity is valuable say against the progressive critique and Hanania’s critique?
Against the progressive critique, I think the Millian has to admit that the progressive has a point. The Millian has to say that certain ways of discussing issues are non-negotiable, and maybe even certain positions (like, perhaps, parts of Millianism itself). If you preemptively rule out debate about things that massive numbers of people disagree about, then this should be disqualifying for you if you’re trying to contribute to human knowledge. This means that it’s ok not to hire people who endorse a return to slavery (because almost no one in the larger populace wants this), but also ok to hire people who are not on board the progressive train about the issue-du-jour, because about half the population, if not much more, is also not on board the progressive train.
But what does the larger population have to do with research? Well, research universities are entwined with polities. To the extent that they get money from taxpayers, they can’t completely ignore taxpayer concerns. This is, first, prudentially sound. If 90% of your researchers high-handedly dismiss views held by 90% of the national population as a sign of bad character, then this invites retaliation from that population. It may also be epistemically sound, because if large portions of the population believe something, it’s probably serving some valuable role in their social ecology — even if it is overall damaging — so it’s hard to say that such views are entirely without value and therefore should be prejudicially dismissed. 
What about progressives who believe (a) – (c)? At this point, large portions of the population believe (a) – (c), so you can’t just rule them out. But, if you rule them in, then progressives either take over or retain control over academia (depending on where you are chronologically).
Here, the Millian may have to take the position that David Lewis defended in Mill and Milquetoast. In that article, he said that he thought substance dualism was clearly wrong, but that it was nonetheless important to have substance dualists around, not because having them around contributes to your finding the truth, but because it prevents you from being lazy (here, Lewis accepts what I called (f) above). But how many substance dualists do you need for this? Lewis estimated (jokingly?) no more than 10% of your population of philosophers of mind. Perhaps Millians could do a similar thing in academia: have around some anti-Millians, but no more than 10% of the professoriate.
OK, but how does the Millian respond to Hanania? Here it’s important to note that there really are distinctions between the humanities and natural science. Natural science is fairly clearly involved in finding the truth; however you define it. By contrast, this isn’t as clear when it comes to the humanities. Consequently, Hanania’s view — diversity is important only insofar as it helps us find the truth — may not apply to the humanities. 
For instance, because philosophy (I’ll focus on philosophy, but I think this goes for all the humanities) is non-empirical, you really can’t be sure you’ve found the truth on anything. You can’t use the natural world to verify that you’re correct. All you can rely on is reason and intuition, the last of which differs dramatically from person to person. Consequently, for philosophy at least, ideological diversity could be more useful.
How much more useful? Well, here it depends on what you think of as the point of philosophy. If you think that the only truly philosophical question is, “Why is there something rather than nothing?” then you’re not going to be super thrilled about lots of ideological diversity. If, on the other hand, you think of the role of philosophy as mapping out the conceptual terrain, then it’s important to have a lot of intellectual diversity, because the more of it you have, the more terrain you can map. Finally, if you think of the role of philosophy as unearthing and understanding a culture’s philosophical presuppositions, then you’re going to need as much ideological diversity as that task takes.
In addition, it’s not clear that philosophy benefits as much from good intellectual hygiene as empirical fields. Some of the most famous and historically important philosophers were not known for their good intellectual hygiene, at least in Hanania’s sense. The first thing that comes to mind when I think about Wittgenstein is not “always open to revising his views” or “engages in cost-benefit thinking,” even though he did have a dramatic shift in view from the Tractatus to the Philosophical Investigations. I would say the same about Kripke and, I’m sure, many others. Indeed, it is arguably those philosophers who are most sure of themselves and least open to changing their minds that often change the field. Whether this is for the better or for the worse is hard to say, when you don’t have the empirical world as a lasso to tie down your loonier speculations.
So, I think the Millian can retain her support for ideological diversity as the paramount kind of diversity that at least certain significant portions of academia should care about. But I don’t think defending ideological diversity is as straightforward as a lot of Millians seem to think, and I think those few remaining Millians in academia and the larger culture should be aware of this, if we ever hope to control any significant cultural institutions again.
 There are indeed such libertarians out there. Some of them, like Noam Chomsky or Bhaskar Sunkara, are “libertarian socialists,” who think that we need to prohibit private ownership of the means of production, because such ownership is the greatest hindrance to the average person enjoying positive freedom. Others, like Michael Otsuka and Hillel Steiner, are “left-libertarians,” who, like many libertarians, believe that everyone owns himself and consequently has strong rights against the state (or anyone else) making you do things with your body that you don’t want to do. Unlike typical libertarians, they do not think you can come to own things by mixing your labor with them, so they end up supporting expansive redistribution of property.
 Lest you think I am being tautological in saying that the best way to increase identity diversity is to have identity diversity, what I’m actually saying is this: it’s very difficult to go from having little identity diversity to having a medium amount of it. But it’s easy to go from having a medium amount of identity diversity to having a lot of it.
 So, one way to figure out the kinds of identity progressives value is to ask: which groups have, historically and currently, been most marginalized on the basis of their identity? And here you will get a dialogue like this:
Progressive: “The identities that have historically and currently been the most marginalized are Black people, Latinx, gender non-conforming people, women, gay people, disabled people, and Muslims.”
Conservative: “And what about people from different countries?”
Progressive: “Well, we also have a duty to have representation of American groups, so that our elite institutions have legitimacy in the eyes of the American populace.”
Conservative: “And what about Jews?”
Progressive: “Well, Jewish people have historically been marginalized, but now they’re doing well. So: no.”
Conservative: “OK, so do you feel the same way about Asians? And what about working class people?”
At this point the conversation devolves.
 What about creationism? This is a view held by a large portion of the population, and yet I and other Millians think it shouldn’t be taught in biology departments. Here, I think my answer depends on the fact that this is a natural scientific position, rather than one that you could expert laypeople to have something valuable to say. Fine, then; what about all the conspiracy theories running amok among half the country? Should we hire people who endorse those? Well, I admit that here things are more complicated, because this is getting into social science issues, and I’m also of the view that these positions are starting to get widespread in part because of the near-unified opposition of the expert class (academics, technocrats, high-ranking federal administrators of bureaucracies, artists) to things that much of the population believes and cares about. So I don’t have much to say about this.
 What about the social sciences? The social sciences are a minefield. I’m not going there, because I don’t want to get blown up.