Explicating Ignorance and Doubt: A Possible Worlds Approach

While the concepts of ignorance and doubt occupy central roles in epistemology as well as in philosophy generally, there have been surprisingly few attempts to give detailed analyses of these notions. We start out by identifying their main conceptual ingredients. We then propose a semi-formal account within the possible worlds framework of epistemic and doxastic logic. The upshot is that while ignorance can be construed as the absence of knowledge of any of the alternatives under scrutiny, doubt is a very special kind of ignorance. We develop two specific proposals for how to capture special features of doubt in our framework. One centers on the notion that doubt, as opposed to ignorance, requires maximum plausibility of opposing alternatives. The other is based on the assumption that, for an agent to doubt a proposition, she must entertain the question whether that proposition is true on her research agenda.