Who should have the authority to influence science in liberal democracies? The epistemic ideal favors the scientific community, whose authority is grounded in science’s unparalleled ability to uncover truths about the natural world. The political ideal seems to favor the citizens, whose authority is based on the democratic principle that legitimacy derives from the consent of the governed. In democracies, tension exists between the epistemic authority of scientists on the one hand and the political authority of the citizens on the other. In this dissertation, I develop and defend a political theory of science grounded in the liberal idea of public reason. Public reason, which requires adopting rules justifiable to all under their authority, is essential for justice in liberal democracies. Rule justification can draw on empirical and normative components, sometimes requiring two forms of agreement: epistemic and political. Roughly, epistemic agreement relates to facts and knowledge, while political agreement concerns values. Many contemporary accounts of public reason in political philosophy have focused almost exclusively on the political component. Yet despite recognizing the need for empirical inputs from experts, these accounts lack the resources to adequately incorporate scientific and other expert knowledge into the political decision-making process. Moreover, they do not address knowledge-generating contexts where non-epistemic values may directly or indirectly influence findings. In the first chapter, I introduce the core issue: the entanglement of values and science in political decision-making. I then argue that a principled political theory addressing these values is essential and worth developing. In the second chapter, I examine the idea of public reason and its relationship to science. I defend a particular conception of public reason that acknowledges the unique role of science in justifying coercive laws. In the third chapter, after examining the aims of science, I defend two desiderata for science in a democratic society and close by developing what I call political epistemic goods. The fourth chapter examines the role of science communication and education within the framework I developed in the preceding chapters.