The marketplace of ideas is a colourful metaphor with a long history of being used to argue for freedom of speech. This paper draws on its historical antecedents to begin with an orthodox understanding of the metaphor whereby the absence of substantive regulation is taken to be conducive to the good functioning of both economic markets and public discourse. This anti-regulation reading is then challenged by analysing a series of legal cases showcasing prohibitions on misrepresentation and fraud. These speech regulations (...) are explained by the economics literature on information asymmetry, which illustrates how honesty regulations maintain good market functioning by facilitating credible reliance by market participants on one another’s assertions. What is thereby proposed is a re-imagining of the marketplace of ideas metaphor which lends support to honesty regulations in the realm of public speech. One potential analogue for these legal and economic findings is identified in the work of Shiffrin and her arguments for deontological sincerity requirements in the public sphere. (shrink)