For most of the twentieth century, philosophers have explored the nature and extent of our knowledge-especially our knowledge of the world grounded in sense-perceptual experience. Can we be sure that our experience of the world is enough to ground our knowledge of an external reality? Are our everyday beliefs about our world warranted well enough for knowledge? What if we're all in The Matrix? This volume collects cutting-edge essays, written by leading philosophers, which address these fundamental questions about our place in the world. Through sustained reflection on two kinds of warrants--entitlements and justifications--they all seek to understand the nature and extent of our knowledge. Even if we were not able to justify our knowledge of the external world, we are nevertheless entitled to our view of external reality.