Abstract: A number of commentators have identified autonomy as a central value of the First Amendment. In this essay, Professor Fallon argues that the two leading conceptions of autonomy, positive and negative liberty, are overly simple and flawed. He argues that autonomy-based First Amendment theory should recognize two alternative conceptions: descriptive autonomy, which considers the impact of external causal factors on individual liberty, and ascriptive autonomy, which represents each person's sovereignty over her moral choices. Professor Fallon introduces a four-part framework to gauge the extent to which a person is descriptively autonomous. He notes that ascriptive autonomy is less analytically neat, but argues that the concept is also important to First Amendment jurisprudence because it "reflects an aspect of human self-understanding that descriptive autonomy fails to capture." Professor Fallon then explores the moral and policy issues that arise from distinguishing descriptive from ascriptive autonomy, concluding that both notions of autonomy are fundamental to the First Amendment. He warns, however, that because descriptive and ascriptive autonomy often pull in opposite directions, autonomy-based arguments frequently complicate rather than simplify First Amendment debates.