What is the correct way to respond to newly acquired information? What methods for updating beliefs and other attitudes are rational? And what makes them rational? This dissertation is a collection of independent essays, each of which addresses these questions. Among other things, I investigate the extent to which Bayesian learning can be considered objective, the circumstances in which rational learning reduces uncertainty and produces consensus, whether rational learning is compatible with disagreement and polarization, and the relationship between long-run and short-run norms for learning.