Assumptions about audiences shape the outcomes of First Amendment cases. Yet the Supreme Court rarely specifies what its assumptions about audiences are, much less attempts to justify them. Drawing on literary theory, this Article identifies and defends two critical assumptions that emerge from First Amendment cases involving so-called “core” speech. The first is that audiences are capable of rationally assessing the truth, quality, and credibility of core speech. The second is that more speech is generally preferable to less. These assumptions, which I refer to collectively as the rational audience model, lie at the heart of the “marketplace of ideas” metaphor, which has long been a target of criticism amongst First Amendment scholars. Now, however, cognitive psychology and behavioral economics provide empirical evidence that the assumptions of the rational audience model are demonstrably false in some commonplace settings. This Article nonetheless contends that behavioral economics has not yet made the case for jettisoning the rational audience model in the realm of core speech. As the Supreme Court has recognized, a legal test that looks at the “actual effects” of speech would be cumbersome and expensive to apply, and would therefore chill speech. But there are even more compelling reasons to adhere to a test focused on the “reasonable interpretation” of core speech. Because speech and expression are closely linked to individual autonomy, government constriction of core speech—particularly political speech—undermines the foundation of a self-governing democracy. Moreover, the rational audience model prevents public discourse from being reduced to the level of the least educated or least sophisticated audience member. The model calls on citizens to raise their cognitive capacities to meet the demands of public discourse, and it serves as a check on the government’s increasingly powerful ability to drown out other speakers in that discourse. This Article concludes that the rational audience model represents a flawed but worthy ideal.