Doubts about truth’s chances of winning the competition in an unregulated marketplace of ideas have already been mentioned above (Ho and Schauer 2015). So the theoretical problem – especially in the context of this project – is to find a way to defend something closely resembling the traditionally liberal right to freedom of speech, in a way that takes into account such doubts about the marketplace of ideas. The problem is not, though, merely to offer some other justification for a right to free speech (e.g. Scanlon 1972).  The problem, rather, is that the marketplace of ideas – much like other markets – may need regulation in order to achieve its desired results. How to reconcile the need for such regulation with the importance of freedom of speech and with liberal worries about state power is a central challenge here, then.

Fully stepping up to this challenge means we will also have to engage with recent discussions in social and political epistemology (e.g. Edenberg and Hannon 2021, Lackey and McGlynn forthcoming): Consider, for instance, “echo chambers”, exemplified by the fact that each person’s Facebook feed is likely to be populated mostly by texts that confirm that person’s already held beliefs, and indeed biases, rather than by sources that challenge them; and by the fact that which news sources one relies on strongly depends on one’s prior convictions and one’s group affiliations. The central role echo chambers play in shaping public discourse is a cause for pessimism regarding the “market place of ideas”. Still, the thought that state power should be used directly to regulate speech is one that liberals have traditionally been averse to, and with reason, it seems. The challenge, then, is to find practical ways of diminishing the effects of echo chambers that are not as dangerous as direct regulation of speech, and to see how to best theoretically understand the nature of the emerging public discourse under such arrangements. Similar challenges arise regarding some other of the phenomena often discussed in the context of social and political epistemology, and indeed the jurisprudence of free speech: “fake news”, conspiracy theories, belief polarization, and the roles of corporations (rather than just of the state) in regulating speech.