This thesis addresses several questions regarding what rational agents ought to believe and how they ought to act. In the first part I begin by discussing how scientists contemplating several mutually exclusive theories, models or hypotheses can reach a rational decision regarding which one to endorse. In response to a recent argument that they cannot, I employ the tools of social choice theory to offer a ‘possibility result’ for rational theory choice. Then I utilize the tools of judgment aggregation to investigate how scientists from across fields can pool their expertise together. I identify an impossibility result threatening such a procedure and prove a possibility result which requires that some scientists sometimes waive their expertise over some propositions. In the second part I first discuss the existing justifications for a restricted principle of indifference that mandates that two agents whose experiences are subjectively indistinguishable should be indifferent with respect to their identities. I argue that all existing justifications rely on the same mistaken reasoning behind the ‘staying’ strategy in the Monty Hall problem. Secondly, I show this mistake is more widespread and I identify it in arguments purporting to show the failure of two reflection-like principles. In the third part I look at a recent argument that fair policy makers face a dilemma when trying to correct a biased distributive process. I show the dilemma only holds if the correction has to happen in one-shot. Finally, I look at how we ought to design public restrooms so that we reduce the discrimination faced by minority groups. I make the case for opening our public restrooms to all genders.