Knowledge and Certainty

This dissertation is a defense of an infallibilist theory of knowledge. According to this theory, we know all and only those propositions that are certain for us. In chapters 1-2, I clarify this thesis and its implications. In chapters 3-4, I argue that infallibilism is the best explanation of a wide variety of intuitions about the nature and roles of knowledge. This is because infallibilism entails or makes plausible various intuitive claims about knowledge, such as that knowledge is evidence and that knowledge can be extended by deduction, whereas fallibilism is either inconsistent with these claims or has a much harder time explaining why they are true. In chapters 5-6, I respond to the charge that infallibilism is an unacceptably skeptical theory of what we know. I argue that infallibilists need not be skeptical of all claims to knowledge – some propositions really are certain for us – and they can give plausible error theories for why we often take ourselves to know propositions that are not really certain for us. In chapter 7, I weigh the overall evidence for and against infallibilism. I argue that, even if some skeptical consequences of infallibilism remain counterintuitive, these costs are more than outweighed by the cumulative benefits of the theory presented in chapters 3-4.