ABSTRACT
How can we determine which epistemic principles are correct, valid, or adequate? One way to motivate concern with this issue is to consider controversial principles. What does it take to be justified in perceptual beliefs about the physical environment? Can I be justified in believing that there is a tree in front of me just by virtue of that belief’s stemming, in a certain way, from a certain kind of visual experience? Or do I also need reasons, in the form of what I know about my visual experience or about the circumstances of that perception? How do we tell what set of conditions is sufficient for the justification of such beliefs? Another and more usual way to motivate concern with the issue is to raise the specter of skepticism. Why suppose that any set of conditions we can realize is sufficient? No matter what experiences and beliefs I have, couldn’t they have been produced directly by an omnipotent being that sees to it that there is no physical world at all and that all my perceptual beliefs are false? That being the case, why should we suppose that our sensory experience justifies us in holding any beliefs about the physical world?
