What’s Wrong with the “Marketplace of Ideas”? (2024)

Lisa Herzog

5.1. Introduction

This chapter is about a metaphor that lies right at the intersection of economics and epistemology: the “marketplace of ideas.”1 It immediately evokes visual associations: a farmers’ market, with stalls full of fruits and vegetables and buyers and sellers haggling over prices, or the pit of a stock market, with frenzied shouting and running, illuminated by countless computer screens. The metaphor suggests lively activity, vivid participation, and exchange—and the idea seems to be that just as with goods and services, the better offer wins out, in a kind of sorting process in which good ideas are picked over bad ones, maybe even leading to something worthy to be called “truth.” With its focus on spontaneity and exchange, the idea is related to, but not structurally identical with, the epistemic defense of markets that I discussed in the last chapters. Here, the point is not so much that markets process dispersed knowledge, but rather that in a process that somehow resembles the market process, truth wins over falsehood.

If the claims implicit in the metaphor of the “marketplace of ideas” were correct, then many issues that I discuss in this book would simply not arise: laissez-faire would lead to truth. But unfortunately, things are not so simple. In this chapter, I discuss several reasons why the metaphor fails: systematic epistemic deficiencies (i.e., it does not work well as a metaphor), historiographic inadequacies (i.e., the historical authors quoted in its support meant something different), and normative indeterminacy (i.e., contrary to its standard use, it does not help us in determining what should be done).2 After briefly describing where the metaphor was claimed to come from (section 5.2), I discuss a number a number of problems with the items at stake. “Ideas” cannot be “traded” in a straightforward way, and it might not even be clear what “trading” them means—not least, and this is a point overlooked in the debate so far, because of the psychology of “holding” or “giving up” ideas (5.3). Moreover, the metaphor is based on a historiographic misunderstanding: neither Milton nor Mill spoke about a marketplace; instead, they evoked pictures of a battle. Therefore, in the next section (5.4), I explore what shifting to the metaphor of a battle can tell us about the processes in which knowledge is generated out of ideas, and why it makes sense—if one wants to keep a metaphor—to shift to a metaphor of playful sporting competitions, in the plural, instead. This leads to some key questions that these various metaphors bring up: the role of motives, the legitimacy of regulation, and the temporal dynamics of knowledge generation (5.5). I argue that instead of assuming one big “marketplace” or “sports field,” a better description of our reality, and also a normatively more adequate picture, is one in which the differences between discursive settings are taken seriously, and regulation differs depending on what the discourses in different fields aim to achieve. I conclude (5.6) by returning to some of the insights from Mill’s historical text, which continue to be challenges today—and which show, if proof were needed, that reading the original texts is more productive than clinging to enchanting, but ultimately misleading, metaphors.

5.2. Historical Sources

In the Anglophone world, two historical sources are standardly cited for the metaphor of the “marketplace of ideas”—though, as I will discuss below, this is not quite justified.3 The first is John Milton’s 1644 treatise Aeropagitica, which argued against the compulsory licensing of books that the Parliament had introduced. As Milton wrote in a famous line: “Let [Truth] and Falshood grapple, who ever knew Truth put to the worse in a free and open encounter?”4 The second quoted source is John Stuart Mill’s 1859 On Liberty, which, in chapter 2, presents an extended argument against censorship. All opinions, even those that are clearly wrong, should be left uncensored, because the “collision with error” leads to “the clearer perception and livelier impression of truth.”5 Only when there is lively debate, Mill argued, can truth remain “living truth,” instead of becoming “dead dogma.” All truths need to be “vigorously and earnestly contested” to remain vivid in people’s minds.6

The metaphor of the “marketplace of ideas” has been particularly influential in US jurisprudence on free speech.7 It was first used in a dissenting opinion in a 1919 Supreme Court judgment, in which Justice Oliver Wendell Holmes Jr. held:

Another representative quotation comes from a 1969 judgment:

Google n-gram shows a massive rise of use of the phrase “marketplace of ideas” since the 1960s.10 Usually, the message carried by the metaphor was the same as the one that would often accompany discourses about all types of “marketplaces” in these decades: governments should keep their hands off these spontaneous processes, because they would, by themselves, lead to positive outcomes.11 Truth does not need any help in winning over falsehood; it might even become stronger in the process—or so the standard use of the metaphor suggests.

And yet the metaphor as such is polysemic. A first way of understanding it is to focus on the exchange of ideas in public meeting places, such as the agora in Greek city-states, or the village square, which both also happened to be marketplaces. But taken in this sense, the metaphor is not very instructive because it says nothing about the mechanism it is meant to describe; moreover, it seems to lose relevance for today, with such traditional “marketplaces” being replaced by malls and online shopping.12 A second way in which the metaphor has sometimes been understood is as a more literal “market”—for newspapers, TV programs, or other media through which ideas can be communicated.13 Some commentators have focused on the competition, or lack thereof, in, say, the market for local newspapers, and have criticized monopolistic tendencies in the provision of news.14 Arguably, however, this has changed with the arrival of the internet. While the platforms on which online communication takes place show similar tendencies toward monopolization, what happens on these platforms is, arguably, a relatively free exchanges of ideas. Whether or not it has led to truth winning over falsehood, however, is precisely the question.

In what follows, my focus will be on a reading of the metaphor that looks at the process that, allegedly, leads to true knowledge, out of the ideas brought together by individuals in something like a market. However, when one starts thinking about the analogies between market processes and the processes in which ideas are exchanges and knowledge is generated, it quickly becomes clear that there are more differences than similarities. In fact, in academic debates the metaphor has long been criticized. As two commentators have held: “At best the metaphor is incoherent, at worst pernicious, as when it encourages us to believe that true ideas will always triumph in any contest with falsehood.”15 And yet it continues to be used, both in academic and in nonacademic discourse.16 In the next sections, I argue that it cannot be defended, neither as metaphor nor as claim.

5.3. Why the Metaphor Fails

A market consists of the buying and selling of goods by large numbers of buyers and sellers—at least this is the paradigmatic form that markets take. The idea that drives many usages of the “marketplaces of ideas” metaphor is that there is a spontaneous, quasi-automatic adaptation of supply and demand in which better offers win over worse ones, leading to efficient outcomes. Something similar is, supposedly, happening in the “marketplace of ideas”: an “invisible hand”—to evoke another powerful metaphor—guides the process, so that no visible interferences are needed. But how good is the analogy between markets for goods and markets for ideas? In what follows, I discuss several ways in which this analogy fails, with implications for the overall message that “spontaneous” processes could sort truth from falsehood.17 I argue that this message is indefensible, especially given the psychology of what it means to “trade” ideas. While some arguments have already been brought forward in the literature, I add new perspectives on the psychological dimensions, on the differences between allocative efficiency and the outcomes of knowledge processes, and on the temporal dynamics of epistemic processes.

First, what is being traded? When a good or service is traded in a market, it needs to be “commodified”: it needs to be understood as a separate item that can change hands for money.18 Some might object to the very idea of a “commodification” of knowledge that the metaphor suggests, holding that knowledge should never be a mere “market product,” bought and sold (and maybe speculated with) at will.19 But even on a much more pragmatic level, there are challenges to thinking about “ideas” as such tradeable items. Tradeable items need to be separable from each other; ideas, in contrast, always stand in connection with other ideas. They can only be understood as part of broader bundles of assumptions, vocabularies, and argumentative structures. This is why Robert Sparrow and Robert Goodin suggest that there are “network effects” between ideas, because their value depends on their connection to other ideas.20 Network effects, however, are a challenge for competitive markets: they often push them toward monopolies.21 This throws first doubts on the idea that an unregulated market of ideas would indeed be efficient.

Moreover, ideas have some characteristics of public goods: if one “gives away” an idea, one does not thereby lose it.22 As commentators have pointed out, even if more and more people share an idea, it does not lose its value, and the marginal costs of handing it out are often close to zero.23 We might try to exclude others from an idea by keeping it secret—but then we cannot at the same time offer it in the marketplace to other potential buyers.24 All these factors mean that the language of “trading” does not make much sense; what we usually say is that we “share” ideas.25

Let me add some additional problems. One is that even if one wants to get rid of an idea, this cannot easily be done—our memories are not under our conscious control, and ideas might come back and haunt us even if we wish we could have “sold” them without a remainder. Moreover, not all ideas can simply be “shared”: some are hard to acquire because they require understanding other concepts or arguments or having had certain experiences. One can hardly “pick them up” in the way in which one picks an apple from a fruit stall. This leads back to the questions about expert knowledge I have discussed in previous chapters: if it takes years of training to acquire certain ideas (or certain forms of practical knowledge), the proposal that such ideas could simply be made available to all citizens is naive. Instead of “trading” them, a relationship shaped by professional responsibility is required—or so I will argue in a later chapter.

This leads to a second set of questions: what would the analogy to “trading” be? A first point to note here is that the preferences individuals are assumed to have in markets concern the single-minded pursuit of their interests. Neither altruism nor the willingness to pursue common interests has a place in paradigmatic models of market competition.26 But what, then, are individuals’ preferences in the alleged “marketplaces of ideas”: to maximize truth or to receive something else? Do individuals maybe seek “comfort and reassurance,”27 or even “drama, sex, violence, and comedy,” as some commentators have suggested?28 If this is what they seek, this is what the market process will likely provide—and that means that it may lead to many things apart from truth.29 If individuals are partly interested in truth and partly in other items, one would expect a “market” process to provide a mixture of truth and other things. But individuals may then not be able to sort out the truths from the mixture on offer,30 and they might pick up falsehoods on the way.31 In any case, it is not the market process as such that sorts truths from falsehoods for them.

What commentators have failed to discuss, however, is that the metaphor of a “marketplace of ideas” suggests that individuals are eager to offer and receive ideas, and voluntarily part with ideas that are defeated by better ones. But not all ideas are such that individuals would simply want to trade them away, as if they were some random market products. Some ideas, beliefs, and convictions are part of individuals’ identity—giving them away means cutting out chunks of the fabric of emotions, convictions, and memories that make up one’s self.32 Neuroscientists have found that the human brain reacts to information that challenges individuals’ “deep convictions” in the same areas that are also responsible for the human sense of identity and for negative emotions.33 The instinctive reaction to certain pieces of information or certain kinds of arguments is not to welcome them with open arms, if only the price is right, but to become defensive. Changing one’s views can be a years-long, painful process, nothing like the “exchange” of goods and services in a market in which one stands back from one’s transactions and remains the same person as before.

Because of this unwillingness to give up certain ideas, one might not get a marketplace, but rather shouting games between fragmented and polarized groups that share certain ideas within the group but are unwilling to “exchange” them with out-group individuals. Instead of even inspecting the other sides’ “wares,” many individuals seem annoyed by the mere fact that views contrary to their own ones are on offer. Describing US public discourse, and in particular many people’s reactions to expert claims, Tom Nichols speaks of “a solipsistic and thin-skinned insistence that every opinion be treated as truth.”34

But note that even if all individuals were purely truth-oriented, the analogy with a market process of trading continues to be misleading—again a point not yet noted in the literature on the marketplace of ideas. Truth, the presumed outcome of the marketplace of ideas, is the same for everyone, at least in principle. As such, it is fundamentally different from tastes or preferences. One of the great advantages of markets is that they can offer a variety of options, for individuals with different preferences, and allow them to exchange goods and services so that everyone finds whatever is the best fit. With the marketplace for ideas, however, it is different: what one hopes for is a process in which a common ground is established, because truth “wins” and is accepted by everyone. The idea is not that bad arguments and wrong hypothesis find their eager buyers, in some market niche, but rather that they are weeded out and rejected once and for all. What one hopes to end up with is not a distribution of different things, but a position that can be widely shared, because all good arguments have been integrated in it and it has been defended against all relevant objections. And yet, for many areas, the picture of different suppliers catering to different purchasers seems to be a more adequate description of the current reality, especially when one considers online discussions and the fragmentation of discourse into various online forums.35

Given these disanalogies, it should not come as a surprise that the metaphor of the marketplace of ideas leaves open some of the most urgent political questions around public speech. In this sense, my conclusion is that the metaphor is normatively indeterminate. While the metaphor has often been used, especially in US contexts, to argue against government regulation regarding the provision of ideas,36 it is not clear that this follows. After all, many markets for goods and services do require regulation,37 and some commentators have in fact argued for regulation on the basis of the market analogy.38 Just like other markets, the marketplace for ideas might exhibit “market failures”39 or create “negative externalities”40 that require government intervention. But how should one decide what counts as “market failure” or “externality,” and what is part of the normal market process? As a matter of fact, in almost all countries there are restrictions on the supply of certain kinds of “ideas,” for example, through libel law or bans on child p*rnography.41 But the marketplace metaphor in no way helps to decide which speech should be regulated and in what ways—a point to which I come back below.42

One issue in particular has raised questions about the need for regulation: the lack of a level playing field, which can mar both markets in goods and services and markets in ideas.43 On the one hand, this inequality concerns the market players: they have unequal financial power and thus unequal opportunities to “buy” or “sell” ideas.44 But arguably, ideas themselves (and, by implication, their suppliers) are also unequal: ideas that are more emotionally appealing, fit more neatly into existing narratives, or are simply easier to grasp usually find more “buyers.” And of course, the spontaneous appeal that an idea has with a particular audience is no criterion for its truth; sometimes, it is precisely the true claims that are least popular. But whether or not (and if so, in what ways) government regulation could help establish a “level playing field” is far from clear—what would it even mean to make certain ideas more attractive? Once more, the metaphor raises more questions than it answers.

5.4. Markets, Battles, or Sport Games?

Why, then, would thinkers like Milton and Mill come up with such a weird metaphor? Was it mere rhetorical flourish? In fact, the ascription of this metaphor to Milton and Mill is a misattribution, which academics have copied from each other and thereby created a narrative of its own. The associations evoked by Milton and Mill are those of competition in battlefields or sporting contests rather than marketplaces; none of them speaks explicitly about a “marketplace of ideas.”45 Milton in one place explicitly rejects such rhetoric: “Truth and understanding are not such wares as to be monopolized and traded in by tickets, and statutes, and standards. We must not think to make a staple commodity of all the knowledge in the land, to mark and license it like our broadcloth and our woolpacks.”46

The metaphor of exchanges of ideas as competitive battles continues to be used. “Argumentation as war” is one of the key examples in Lakoff and Johnson’s Metaphors We Live By.47 Many commentators have criticized this metaphor, which seems to suggest that argumentation is about winning or losing, rather than about both parties gaining from the exchange of arguments and perspectives.48 It is crucial, however, to read the metaphor with precision: it is meant to be a battle of ideas, not of individuals. Ideas are abstract entities, and so the question becomes how the struggle between them can be instantiated in real life.

If read in this way, the metaphor has interesting implications, and we can, in fact, gain some interesting insights on the preconditions of discourses leading to the truth. For a battle of ideas can only take place if individuals, as the bearers of ideas, behave in certain ways—and these are precisely not purely combative (or, for that matter, commercial). Instead, individuals need to be willing to let the ideas engage with each other, and to go where these encounters take them, even if means that their own ideas suffer a blow or are completely defeated. In other words, while they may certainly enter the exchange with the hope that their ideas will win and try to present them in the best possible light, this must not be their only motive.

If one wants to keep a metaphor in place, let me suggest one that might express this idea better than that of a “battlefield”: that of a sports contest. But for that metaphor to make sense, the sports contest needs to be understood as one that is not only about winning, but rather about excelling at certain techniques, providing a “good game,” and maybe also having fun together.49 Understood in this way, this metaphor underlines that individuals need to have a sense of sportsmanship: they need to respect the integrity of the contest and its rules, treat their opponents with fairness, and be willing to accept defeat where appropriate. The benefit they receive, even if their own ideas lose, is an increase in insight, if truth indeed wins over falsehood.50

In fact, my proposal can be supported by returning to the historical texts by Milton and Mill. According to Philip Kitcher, Milton assumed that the “encounter in which Truth and Falsehood grapple, must be fair and open,” and that the evidence for and against a certain proposition must always be evenly evaluated.51 Mill similarly states that “only through diversity of opinion is there, in the existing state of human intellect, a chance of fair play to all sides of the truth.”52 He admonishes his readers to follow the advice of Cicero to always study one’s “adversary’s case with as great, if not with still greater, intensity than even his own.”53 For ideas to have a fair battle, the individuals who carry them into it need to have an ethos that complements the will to win with a generous amount of sportsmanship—so much that, in case of doubt, one’s will to let truth win over falsehood is stronger than one’s attachment to the ideas one brought to the sports field.

This also means that the social settings in which contests of ideas take place must not be organized in too competitive a way, because this would undermine the ethos of sportsmanship, which creates a cooperative basis for the competition itself.54 If the competition of ideas turns into a competition of individuals or interests, this can lead to strategic behavior, such as hiding arguments or stealing ideas from others. Such maneuvers can be highly detrimental for the search for truth; they can, for example, delay the rejection of falsehoods or lead to the unjustified exclusion of highly promising ideas.55 The result can be suboptimal allocations of intellectual energies and resources, or even preventable harm to those who suffer from uncorrected falsehoods.

Thus, my claim is that if one searches for a metaphor that captures the attitude individuals should have when entering what is so misleadingly labeled the “marketplace of ideas,” it is the comparison with sports that is more helpful. But for such a sports tournament of ideas to take place, high demands are put on individuals: instead of maximizing their own gains, as the marketplace metaphor suggests, they need to be sufficiently detached from their ideas to give them up if they turn out to be defeated by better ones. It is only when these conditions hold that the “competition of ideas,” as one might then call it, has a chance of bringing us closer to the truth.

5.5. Different Fields, Different Rules

The metaphors of the “marketplace of ideas,” of “competitions of ideas,” or of “tournaments,” like all metaphors, shed light on certain aspects of reality at the neglect of others. In this section I want to make explicit some aspects that the discussion so far has brought to the fore. I argue that a number of systematic questions need to be answered for the different fields on which ideas encounter each other. Importantly, however, there is no reason to think that they need to be answered in the same way for all fields. On the contrary: often, they need to be, and in fact are, answered differently. Different kinds of sports tournaments, after all, also take place on different fields, with different kinds of rules and different ways of determining success. Arguably, one of the ways in which the powerful rhetoric of a “marketplace of ideas” has been harmful is precisely that it has obscured these differences, suggesting that all discourses should be treated the same. I develop the parameters of these decisions that arise from the previous discussion, because it is by focusing on these parameters that we can get to the real questions of institutional design concerning different “competition of ideas.”

A first set of questions concerns the role of the motives and intentions (or “preferences,” in the economistic language of the marketplace metaphor) of individuals: are they driven by a desire to find the truth, or do they have a stronger desire to defend their own ideas? The question can be asked on a descriptive and on a normative level: what is the case, and what should be the case? It may be tempting to think that individuals should always be oriented toward the truth, but this reaction is too quick. For one thing, truth orientation can only be a normative requirement if there can be truth about a matter. We smile at the toddler who wants to know whether chocolate or vanilla ice cream is truly better, but the question is a serious one when there is disagreement about whether or not certain areas are such that there is a truth of the matter or not.56

For another thing, even if there may be an abstract “ought” with regard to truth orientation, one needs to have a closer look at the social settings in which certain exchanges of idea takes place, to see whether it can be realistically expected from individuals. For example, if crucial interests such as one’s physical integrity or the pursuit of important life goals are at stake, it may be problematic—even from a normative perspective—to expect individuals to be oriented toward nothing but the truth. Lying or otherwise obfuscating the truth may even be morally excusable. This means, in turn, that in settings in which it is important that individuals be truth-oriented, potentially distorting factors are, as far as possible, removed. For example, it is easy to postulate that scientists should always be willing to give up hypotheses that are contradicted by new evidence—but if not only one’s reputation, but also one’s position and income depend on the ability to defend certain hypotheses, one should not be surprised that some are unwilling to do so. What should be a friendly tournament characterized by an ethos of sportsmanship can then indeed become more battle-like—and this may have detrimental consequences for the pursuit of truth.57

A second set of questions concerns the legitimacy of regulation—and this offers the opportunity to respond to a potential objection. As I have argued above, the marketplace metaphor leaves this point open, even though it has mostly been used for arguing against regulation. It is worth noting that in contexts in which conduciveness to truth is paramount, such as court proceedings or research institutions, speech is, as a matter of fact, highly regulated.58 Typically, this regulation concerns not so much what can be said, but rather consists in strict procedural rules about how things are to be said, for example, how arguments are supposed to build on each other or who can speak in which order. But most scenarios in which the “marketplace of ideas” is evoked concern public discourse in a broader sense—and the question is precisely whether or not regulation can be appropriate here, and if so, of what kind. This question has been controversially discussed by defenders and critics of (various forms of) “free speech.”

The basic problem here is, in fact, analogous with the other regulations of marketplaces: on the one hand, the system as a whole might deliver better outcomes when it is regulated more strictly; on the other hand, there are individual rights that must not be violated. In fact, the conflict is here sharper than in the case of other marketplaces. In the latter, what is at stake are individual economic rights—to trade with one’s property—whereas in the “marketplace of ideas,” what is at stake is the individual’s freedom of speech. Arguably, the latter has a deeper justification, and a closer connection to democratic self-governance, than any economic right.

To be sure, if the only justification for the freedom of speech were its role in maintaining a marketplace of ideas, the argument would become circular: if this marketplace is a fiction anyway, then why support the freedom that makes it possible? But this is not the case. There are other, arguably more important, reasons for protecting this freedom (together with the freedom of the press and other freedoms of expression). Some of the most important arguments concern autonomy, democracy, and toleration, and for all, there is an extensive debate, which I cannot summarize here.59 Judith Lichtenberg is certainly correct when she writes, after surveying the various values that commentators have based these freedoms on, “Any ‘monistic’ theory of free speech, emphasizing only one of these values, will fail to do justice to the variety and richness of our interests in free speech.”60

Given this pluralism of values and given the plurality of settings in which speech takes place, we should not expect a one-size-fits-all solution. Just as there are different sets of rules for different markets, or for different kinds of sports competitions, in an epistemically well-ordered society different settings can, and often should, have different rules, giving different weight to these different values and to the importance of the overall quality of discourse. In some settings, the protection of participants from derisive and disrespectful comments is necessary and appropriate; in others, it may be necessary and appropriate to let such things be said (even though it may still be appropriate to morally blame those who utter them). In some, anonymity may be justifiable and even highly valuably; in others, regulation that requires individuals to reveal their identity may have the balance of arguments on its side.61

Let me here add one of the most misleading aspects of the metaphor of the marketplace of ideas, which is perpetuated in the sports metaphor: they both detract attention from the possibility of malevolent players, whose interest is not to trade or to play sports but to undermine the very activities in question. Whether it is the “tobacco strategist” mentioned in the introduction, or the operators of online “troll farms,” their strategic interventions are not at all well captured by images of sunny farmers’ markets or a happy game of football among friends. By evoking such metaphors, especially in the versions that suggest a laissez-faire approach, they insinuate that their own actions are of a kind with those by other participants with honest intentions. However, it is often not feasible to somehow force agents to reveal their intentions, which makes this a difficult terrain for regulation. And yet certain steps are possible to at least exclude the most egregious abuses. Regulation that would, for example, require online messages by electronic bots rather than human beings to be labeled as such is comparable to rules that protect markets against fraud, and rejection of it can certainly not be justified by referring to Milton or Mill.

Often, it also makes a massive difference who speaks. Many justifications for the freedom of speech, for example, those based on autonomy, refer to human individuals. Pace some US legislation, it is not at all clear that corporations and other commercial entities need to have the same freedoms. Corporations, by definition, have economic interests; their intention is to generate profits.62 They do not have the same kinds of political, cultural, and expressive interests that human beings have. To be sure, this does not mean that corporations should have no freedom of speech at all. But when weighing different arguments, their interests in free speech cannot be assumed to have as much weight as those of human individuals. This means that the regulation of advertising,63 or of professionalized (in contrast to private) climate change denialism,64 or of speech by pharmaceutical companies on the effects of drugs,65 may be perfectly legitimate.

Rather than drawing a false analogy from human speech to corporate speech, a key question for many fields of discourse is whose speech might, as a matter of fact, be excluded, even though these individuals or groups have justified claims to speak and to be heard. In many fields, formal and informal practices create barriers for members of minority groups, or of groups that have not traditionally been part of these discourses. While regulation is not the only possible response to such problems, and not always the most effective one, it can sometimes contribute to bringing in more perspectives. Such regulation usually concerns the broader framework rather than specific utterance: it is what Lichtenberg calls “structural regulation.”66 It can include, for example, regulation of the ownership structure of media companies, support for news outlets that cater to minority communities, or subsidies for public broadcasting organizations that represent a plurality of voices. If this takes place within a democratic system with checks and balances and the rule of law, the risk of sliding into state censorship—which Milton and Mill were most worried about67—is minimized.

It is also important to note, however, that not all discourses are, or should be, truth-conducive—and hence, it is imperative to also leave room for other kinds of exchanges. What matters is that individuals know what kind of setting they are in: what they can expect from it, and what the appropriate norms of behavior are. In fact, many problems in public discourse, and the controversies around them, concern a lack of clarity about the kind of discourse one is in, or issues concerning the transitions between different discourses. For example, when statements are taken from the sphere of an expert community to public discourse without being properly contextualized and explained, abuse can easily happen. Arguably, it is the confusion, whether intentional or unintentional, of the rules of different settings of discourse that creates many of the epistemic challenges our societies face today. By creating more clarity about the boundaries, and about the norms that hold in different settings, many problems would become more manageable.68 This is why I see the clear delineation and demarcation of different discourses as a key question for an epistemically well-ordered society.

Related to this is my last argument, namely the different temporal dynamics that characterize different spheres of discourse. In some spheres, it makes sense to speak of an increase in knowledge and a reduction of falsehoods over time. For example, we now do know more about the causes of climate change than in the 1970s. In other spheres, it seems much harder to expect progress; instead, there are multiple values at stake, between which new compromises need to be sought by each consecutive generation. But again, it matters which is which: in a sphere in which we can expect progress it does not make sense to keep repeating arguments that have already been decisively refuted. The earth is not flat, and scientists do not have any responsibility to “prove” this again and again.69

To be sure, this shifts the conflict to the metaquestion of which discourse is which—but at least in some cases, this is something on which it might be easier to come to an agreement. Certain questions clearly are scientific questions; others clearly are not, and while there may be a gray area in between, it is often helpful to clarify the status of those that are black or white. This can help to avoid clear misapplications of arguments about the nature of different spheres of discourse. For example, the “fair balance doctrine” in journalism—which has been justified by referring to the preservation of the “marketplace of ideas”70—is misapplied when it concerns the topic of climate change, which is scientific, not political, in nature. And yet, it was applied to that topic for years, leading news outlets to always invite both a defender of anthropogenic climate change and someone who rejected it. Still in 2017, this doctrine motivated the New York Times to hire a climate change skeptic, a move that rightly drew a lot of criticism.71 This was, in my reading, a confusion of different fields of discourse: while “always showing both sides” is the appropriate strategy for questions of values and interests, for scientific issues that have reached a level of certainty as high as that concerning anthropogenic climate change, it is simply a mistake. While it remains speculation whether the metaphor of the marketplace of ideas had play any direct role in this decision, this broader way of thinking about exchanges of ideas should have become transparent as what it is—a misleading image.

5.6. Conclusion

In this chapter, I have discussed some of the misunderstandings, and misapplications of arguments, that flow from the metaphor of the marketplace of ideas. To be sure, I have nothing against rhetorical flourish, and some applications of this metaphor may be perfectly harmless. But once one looks into the details of what it would mean to “trade ideas,” the lack of fit becomes evident. Historical authors to whom the metaphor has been ascribed in fact did not use it. They rather used the analogy with battles or sporting competitions, but between ideas, not individuals. Instead of letting a picture hold us captive, as Wittgenstein put it,72 we need to ask substantive questions about specific contexts in which ideas are exchanges: questions about the motives of participants, about the appropriateness of regulation, and about the temporal dynamics in different fields.

These temporal dynamics can create a challenge when we want politics to be based on the best available insights in an area—a point that Mill, for one, was well aware of. It is often necessary to act, individually or collectively, on the basis of knowledge that is not yet established beyond doubt (i.e., where we know far less than what we know about anthropogenic climate change, where doubt is no longer reasonable). Mill wrote that “in the meantime we may rely on having attained such approach to truth, as is possible in our own day,”73 and apparently did not think that this was a matter of “robbing the human race; posterity as well as the existing generation”74 of dissenting opinions. Basing current decisions on the current state of the art is not the same as suppressing serious, methodological research about potential shortcomings or biases of this state of the art.75 But in practice, this balance can be hard to find, especially if certain actors have strategic interests in denying the reliability of the state of the art.

There is a second noteworthy reminder that we can take from Mill. He strongly warned against individuals accepting truths merely as traditional claims that are handed down to them without explanations, so that they may become “dead dogmas.”76 This warning reminds us that accepting something as true and accepting it as the kind of “living truth” that matters for one’s life are different things. Mill recommended certain pedagogical strategies, such as Socratic dialectics and medieval disputationes, as methods for bringing certain messages home in a deeper sense—a kind of staged sporting competition, if one likes, that can have great pedagogical value, but that is at a far distance from questions about whether long-refuted falsehood should be allowed to circulate without any check in public discourse.

True statements, as such, do not automatically bring the kind of reflection and acceptance that would lead to a genuine “appropriation,” in the sense that certain contents become part of the sets of convictions that guide one’s actions. But this problem of denial cannot be resolved by the alleged gymnastics of a marketplace of ideas—for even if certain ideas are under massive pressure, this does not imply that those who defend them will truly take the arguments to heart, let alone change their behavior. The debate around climate change provides many sad examples. This problem, however, needs to be addressed without being misled by a metaphor that mischaracterizes the nature of ideas and knowledge and directs attention away from the most pressing question.

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