Groups are all around us: families, teams, corporations, committees, nations, and so on. We interact with groups, are members of groups, and we blame or praise groups for how they act. Despite being so familiar, unpacking the nature of groups and their constitutive group members presents serious philosophical puzzles. In response to these puzzles, some take the route of dismissing groups; groups are merely shorthand for something that reduces to the individuals that make up the ‘group’. I reject this eliminativism and opt for a robust realist conception of some groups. But this raises the task of showing how groups are built up out of individuals in such a way that explains our experience of groups and does not just reduce to the individuals themselves. My core thesis in the dissertation is that a democratically structured group—a group wherein every member has equal standing, broadly construed—has propositional attitudes that can be determined by the Steward Approach. The Steward Approach posits a Steward, a rational agent whose evidence is all and only the honest testimony of the group members. The group attitude is identical to the set of rational attitudes that the Steward can have. This approach has several virtues. First, it is a positive and solvable approach. Epistemologists generally agree that there is an answer to the question of what is rationally permissible in any given evidential situation, despite the difficulty of determining what response is rational in some cases. Second, this approach bears fruit in sidestepping the impossibility theorems that indicate such a solution is not to be found. Third, and most importantly, this approach gives intuitive results that jive with our common-sense understanding of groups. I conclude the dissertation by highlighting applications of my Steward Approach to different domains, notably the problem of peer disagreement and voting norms. In developing the Steward Approach, I develop tools that can be used to solve the problem of peer disagreement. And, whenever the consent of groups plays a moral role, the Steward Approach is important. It can be used to ground certain group voting structures: a just voting structure is one that, among other considerations, will respect the propositional attitudes of the democratically structured group. There is considerable fertile ground for fleshing out the implications of a solution to the attitude aggregation problem.