The following essay is excerpted from Viewpoint Diversity: What It Is, Why We Need It, And How To Get It, edited by John Tomasi and Bernard Schweizer, released today by Heresy Press.

Every scholar endorses viewpoint diversity. Disagreement is the fuel on which the academic enterprise runs. If scholars all held the same view on every topic under study in the humanities, social sciences, and STEM fields, publication and scholarship would end. Even Lisa Siraganian, a self-styled critic of viewpoint diversity, concludes a broadside against that concept by acknowledging this fact: Scholarly thinking “benefits from exposure to different ideas.”

So, the question is not whether scholarship requires a diversity of viewpoints. The question is: How much viewpoint diversity do we need? Since most of the heat around this question concerns the appropriate range of ideological diversity, I shall focus on that issue. What degree of ideological diversity does responsible scholarship and teaching require?

Public records studies reveal that the professoriate has been steadily skewing ever more heavily left than right. Without any course-correction, that trend looks set to increase, perhaps dramatically. According to studies gathered by John Ellis, the ratio of left-leaning to right-leaning tenure-line professors was roughly 2:1 in 1969; 5:1 in 1999; 8:1 in 2015—and among junior professors, that ratio now stands at a whopping 49:1. As Sam Abrams has documented, studies showing a wide imbalance between liberal and conservative professors have been replicated across many disciplines as well across the professoriate as a whole. No serious scholar disputes the fact of a growing imbalance.

The increasing ideological homogeneity of the professoriate has been accompanied by a contraction in the range of ideas that students encounter in the classroom, as demonstrated by a recent national study of undergraduate syllabi. Most alarming, the study finds, this narrowing range of viewpoints presented to students has occurred especially on hot-button issues on which mutual understanding and bridge-building presumably are most needed: the conflict between Israel and Palestine, racial bias in the criminal justice system, and abortion.

Although no serious scholar disputes the ideological imbalance of the professoriate, people do dispute the significance of this fact. There are at present two main views about viewpoint diversity—each locked in opposition to the other.

On one side are defenders of the status quo, such as Lisa Siraganian and the American Association of University Professors (AAUP). In the face of the facts just mentioned, they reject the idea that the academy today suffers from any “viewpoint diversity problem” at all. Defenders of (their own) expertise, this side says the range of viewpoint diversity within the academy should be whatever the cohort of professors currently inhabiting the university deems fit. Since the existing ideological distribution within the academy arose through processes of scholarly decision-making (the professoriate’s own hiring and promotion decisions, the selection of research topics, the range of readings assigned in their classes, etc.), that distribution is therefore legitimate. The process of applied expertise sanctifies the product—whatever distribution might be produced.

On the other side are those who see the disparity between left- and right-leaning professors as a problem, while viewing that problem in explicitly political terms. This side sees the imbalance within the academy as a kind of injustice, the effective capture of a set of publicly funded institutions by one political party for its own benefit. Since the university system is entrusted with producing research that informs political decision-making, as well [as?] being tasked with educating the next generation of citizens, any ideological imbalance within the academy is a matter of public concern. As a remedy, they seek a political imposition of more balance within the political orientation of the professoriate, so that the ratio more closely (or at least less distantly) represents the political beliefs of the surrounding society.

These two views dominate debates about viewpoint diversity today. I am skeptical of both. But I also believe that we have something to learn from each. Seeing what is right (and wrong) about these two views points the way towards a third view. This view would bring intellectual humility to the claims of expertise, while reconciling the claims of ordinary politics to the special nature of the university.

1. The Scholarly Sanctification View

How wide a range of viewpoints should be welcomed on our university campuses? In the flagship publication of AAUP (American Association of University Professors), Academe, Lisa Siraganian offers a provocative answer to this question: The university should be exactly as viewpoint diverse as the professors who currently inhabit it think fit, and no more. She explicitly criticizes Heterodox Academy, and me, for advocating a wider range of viewpoints. I’ll return to that point. For now, notice that while I just described Siraganian’s thesis as provocative, until very recently there was nothing at all provocative about her view. Indeed, for decades Siraganian’s thesis served as a rarely questioned academic state of affairs.

The concept of viewpoint diversity burst on the political scene in 2002 with the publication of David Horowitz’s “Academic Bill of Rights.” Noting the increasingly one-sided political party orientation of the professoriate, Horowitz argued that universities should seek greater pluralism and diversity. Although Horowitz used the phrase “intellectual pluralism,” it was the term “viewpoint diversity” that captured the popular imagination (an n-gram of that phrase from 2002–2004, measuring popular usage, resembles the steep face of Mont Blanc).

By 2003, the AAUP’s Committee A had issued a response to Horowitz. Their conclusion was that “decisions concerning the quality of scholarship and teaching are to be made by reference to the standards of the academic profession, as interpreted and applied by the community of scholars who are qualified by expertise and training to establish such standards.” How wide a range of views and opinions should be studied and taught on our campuses? Siraganian in 2025 and Committee A in 2003 agree: Universities should study and teach a range of viewpoints that is as wide, and no wider, than whatever group of professors currently inhabit the university believes appropriate.

As I’ll explain in a moment, I find this approach implausible. But I share two key premises with Siraganian and the AAUP. The first is that the primary purpose of the university is the pursuit, preservation, and dissemination of knowledge. The second is that disciplinary standards are central to that purpose. Expertise matters, and any serious view of viewpoint diversity should recognize that. So far, so good.

The problem, however, is that there is a hidden third premise that Siraganian and the AAUP also rely upon to defend the status quo. This is the assumption that when people pass through the process of training and professionalization needed to enter the professoriate, they somehow leave behind the psychological biases and vulnerabilities to groupthink that are part of human nature. Siraganian and the AAUP believe that the process of academic professionalization sanctifies the collective decision-making of the professoriate. Thus, whatever decisions the professoriate makes about hiring and promotion, and whatever overall pattern emerges from those decisions, are ipso facto justified by the fact that the pattern arose through professors exercising their professional expertise.

As the AAUP statement put it in 2003: “The appropriate diversity of a university faculty must ultimately be conceived as a question of academic judgement”. So, if an overall pattern emerges across the academy in which conservative and libertarian scholarship and reading assignments become ever more marginalized, as has happened, this is nothing to worry about—so long as each decision leading to that pattern was made according the existing professors’ own expert judgment. There is no external standard that could be used to explain why the ideological narrowing of the academy might be anything to worry about. The opinion of the professors currently in the academy controls all: It alone defines the acceptable limits of viewpoint diversity.

As Jonathan Haidt and I have argued, this view is naïve, unhistorical, and strangely uncritical. Professional training does not make professors immune to ordinary human biases. Academics remain human still. And if the ideological boundaries and assumptions of the profession happen to align with the professors’ own ideological boundaries—as can happen when the range of viewpoints in a group shrinks—they may be especially susceptible to bias. Today’s cohort of scholarly experts remains vulnerable to the same “tyranny of public opinion” and “uncritical and intemperate partisanship” that the founders of the American Academy of University Professors in 1915 warned academia to resist.

This idea, that professionalization does not insulate one from bias, is a major finding from the sociology of science. Indeed, recognition of the danger of bias can be seen in core academic practices, such as the doctrine of blind review, or the practice of selecting tenure letter writers from a diverse pool. These practices implicitly recognize that even academic experts remain subject to bias. The cohort of professors who currently inhabit the university remain human, just like every cohort before them and every cohort yet to come.

2. The Political Representation View

Since the filter of scholarly expertise will always remain flawed by human bias, one alternative would be to discard that filter altogether. Siraganian characterizes one such alternative as follows: “The more views you have, the more viewpoint diversity you have.” Whether the view is that the structure of DNA is a triple helix, or the claim that Maoist collective farming was an economic success, or the thesis that the earth is flat and the moon is square, this approach to viewpoint diversity says the more views the better.

The problem with this view is that if you only care about having the greatest number and variety of views, even when expert opinion has decisively shown those views to be false, one loses the connection to truth-seeking, which is the university’s purpose. Yet there is a second problem with this view: To my knowledge, no one holds it.

Because she considers and rejects an implausible alternative to the AAUP’s “simple-sanctification” view, Siraganian fails to consider a more serious alternative that stands closely adjacent to the straw man she sets up. This view, like the-more-views-the-­ better view that Siraganian considers, also rejects that AAUP claim to absolute sovereignty of whatever cohort of humans currently inhabit that professoriate. But it then looks to an external standard to determine when or if the decisions by the professoriate have gone astray.

This view, widely associated with the political right, says that the range of views under active discussion within the academy should be (broadly) representative of the political views held in the wider society—say, as represented by the major political par- ties. I’ll call this view of viewpoint diversity the political representation view.

On the political representation view, if a society is divided roughly equally between people holding conservative and progressive political ideologies, that same range of views ought to be represented in the academy.

Like the principle that “the-more-views-the-better,” the representation view uses an “expertise-free” criterion to decide how diverse the views in the university ought to be. Only by this approach, the boundaries of viewpoint diversity within the academy are tied to political representation. Anyone who, like me, sees the university as fundamentally committed to knowledge-seeking, must reject this view—at least in this simple version. For one thing, if we believe the telos of the university is the search for knowledge, we should expect (indeed, hope for) the occasional achievement of scholarly consensus—even, perhaps, on contested political and moral issues. Further, why would we think having a faculty with more registered Republicans, say, would improve research and teaching in engineering, mathematics, or any other fields? And even within disciplines that do address political topics, why think that representation of the dominant political parties (in any one country, at any one historical moment) should be allowed to set the parameters of scholarly investigation? If our guide is knowledge-seeking, this simple version of the representative view is unattractive.

3. A Third Way: The Heterodox View

The purely internal, expertise-based view of viewpoint diversity—the scholarly sanctification view—is psychologically naïve. And the purely external view—the political representation view—likewise would weaken the commitment of universities to their knowledge-seeking function, just in a different way. So, what is to be done?

At Heterodox Academy, we believe there is a world out there worth knowing, and that disciplinary methods and standards—whatever their defects in practice—are our best chance of gaining that knowledge. Yet we also believe that the rising ideological conformity of the professoriate poses a threat to effective knowledge-seeking, and to the public credibility of our universities as well. This is a threat that the self-governing professoriate, so far, has shown itself unable (or unwilling) to address. But is there a way to capture both these insights in a single account of viewpoint diversity?

I believe there is, and here is the core idea: On every scholarly topic, the tools, norms, and standards of the relevant discipline generate a range of positions that might possibly be considered and defended by experts in that field (each according to their discipline’s evidentiary standards). What is wanted is that a robust range of options on this methodologically identified “frontier” of positions be kept open in a lively way.

To achieve the good of viewpoint diversity in the sense I am proposing, it’s not necessary that every thesis on that range of possibilities is actively being defended within the academy. Many questions—the shape of the earth, the outcome of Mao’s agricultural reforms—have been decisively settled. We may have reason to teach about those questions, but the questions themselves have been settled. Expertise must be given its due.

Yet, from the other side, it is also not necessary that the defense of that (methodologically available) range of theses be politically representative of society. Universities are not essentially political institutions: They are essentially knowledge-seeking ones. Yet intellectual humility teaches us that the opinions of people outside the university can sometimes help us identify systemic biases and blind spots of scholars working within. Even experts sometimes need someone to tell them to check their premises.

This third view of viewpoint diversity is a kind of hybrid of the two dominant views—the scholarly sanctification view, and the political representation view. With its respect for disciplinary standards of evidence, it cares very much for “doxa,” or truth-seeking beliefs. Yet, with its sharp awareness of the vulnerability to groupthink, even of knowledge-seekers, it also has a special concern for difference, or “heteros.” I hope it will not surprise you that I call this third view the heterodox view of viewpoint diversity.

On the heterodox approach to viewpoint diversity, as I have said, what we need is that the methodologically available range of research questions be kept open in a lively way. And this, precisely, is where many of us fear the contemporary university has fallen short.

Consider a few examples. Climate science has a set of methodologies (ways of presenting evidence) that allow for the generation of a range of climate change models. Some predictive models are “hotter” and “faster”; some models are “cooler” and “slower.” To have healthy viewpoint diversity in climate science, we don’t need to have each possible predictive position being defended. Nor do we need to have an “ideological balance” across the range. Again, some degree of scientific convergence is a reasonable academic goal. But if climate science falls into a position where certain (methodologically available) positions cannot even be discussed, then we have failed on the viewpoint diversity standard.

Similarly, the field of international affairs has a set of methodologies that make available a range of positions about the proper relation of (let’s say) the United States of America to the rest of the world. If a scholarly consensus emerges around a liberal internationalist (or cosmopolitan) answer to that question, that’s fine. Again, we are searching for knowledge. But if rival methodologically possible positions (say, the doctrine of American exceptionalism) cannot even be discussed or taught in a serious way, then we have fallen short on viewpoint diversity in our sense.

So too with political or intellectual history. Having lots of scholars writing books that explore the wisdom of Franklin Roosevelt or John F. Kennedy or Ruth Bader Ginsburg is fine. But if scholars committed to those same historical standards of evidence cannot even consider writing a similarly positive book about, say, Calvin Coolidge or Ronald Reagan or Clarence Thomas, then something has gone seriously wrong. The scope of viewpoint diversity has been artificially narrowed, and our ability to search for knowledge has been weakened as a result.

Similarly with medicine and public health. If, during a pandemic, a public health consensus emerges and stabilizes on masking, lockdowns, and vaccines, so be it. But if heterodox positions about pandemic responses—such as the Great Barrington Declaration—cannot even be stated without attacks on the character or motives of dissenting scholars, such that arguments for those alternatives cannot even be considered according to disciplinary standards of evidence, then something has gone wrong with the discipline of public health from a viewpoint diversity perspective.

This heterodox model of viewpoint diversity could also encapsulate yet another form of viewpoint diversity that some defend: identity viewpoint diversity. Many people demand more racial or gender diversity on campus as a requirement of (their theory of) social justice. There are important moral issues here. Now, the heterodox ideal of viewpoint diversity, by contrast, would advocate greater identity diversity precisely because (and precisely when) greater racial or gender diversity opens up hidden (methodologically available) views and research programs, thus making neglected options available in a lively way.

For example, the late twentieth century saw a flowering of historical scholarship on the American Founding Period (Gordon Wood’s 1969 epic The Creation of the American Republic, 1776–1787 is an exemplar). But while historians of this era produced brilliant and illuminating works about the principles and achievements of the leading agents of America’s founding era, the historical role and experience of enslaved Black people in early America, and of other marginalized groups, was hardly mentioned at all. As university faculties and student bodies became more racially integrated in the 1980s and 1990s, historians of early America increasingly turned their attention to those neglected perspectives and experiences—thus potentially enriching historical scholarship and teaching alike. Identity diversity, in this case, had the potential to increase the breadth and power of viewpoint diversity in our sense.

So, we have considered and rejected two “pure” approaches to viewpoint diversity. One, the scholarly sanctification view, is purely internal. It asserts that the boundaries of viewpoint diversity on campus should be set entirely by whatever cohort of academics presently inhabit the academy—no matter their susceptibility to groupthink and cognitive bias. The other, the political representation view, is purely external. It asserts that the boundaries of viewpoints on campus should be set in a way this is politically representative of the wider society—no matter that some of those views and opinions (from both sides) are demonstrably false.

As we have seen, neither of these “pure” approaches can plausibly answer the question with which we started: In a university committed primarily to the search for knowledge, how diverse should viewpoint diversity be? In response, I am proposing a hybrid view of viewpoint diversity, one that seeks to pick up an insight from each of those views while avoiding their defects. On this, the heterodox view of viewpoint diversity, what is wanted is that a robust range of (methodologically available) ideas and opinions be kept open in a lively way.

Siraganian writes: “[T]hose of us who want good ideas to win and bad ideas to lose should understand that viewpoint diversity will not get us there.” The opposite is true. If we are to have any hope that good ideas will win and bad ideas will lose, we need a wider range of views to be kept open in a lively way at our universities. As the examples mentioned above demonstrate, such views often arise from real debates occurring in the surrounding society—not just from intramural scholarly discourse. Views kept open in this way do not get a free pass simply because they are different from mainstream views of the professoriate at any given moment. Nor do they have any special standing for that reason. But nor do such views get shut down without examination. Instead, for views to be kept open in a lively way means that such views are welcomed into the field of disciplinary contestation, where they will be judged, and must be defended, according to disciplinary methodologies and standards of evidence.

This is a heterodox, knowledge-tracking approach to viewpoint diversity. It recognizes that group opinions, even of experts, can sometimes go badly wrong. While firmly committed to disciplinary methods and standards of evidence, this heterodox approach also reflects a form of intellectual humility appropriate to scholars, who should be ready to recognize that, despite all their degrees and qualifications, they sometimes have things to learn from people who live and work and form opinions outside the ivory tower.