Economists tend to view ignorance as ?rational,? neglecting the possibility that ignorance is unintentional. This oversight is reflected in economists? model of ?information search,? which can be fruitfully contrasted with ?information browsing.? Information searches are designed to discover unknown knowns, whose value is calculable ex ante, such that this value justifies the cost of the search. In this model of human information acquisition, there is no primal or ?radical? ignorance that might prevent people from knowing which information to look for, (...) lacking omniscience. Unlike ignorance that is rationally chosen on the basis of an accurate cost/benefit calculation, radical ignorance can explain human error. An account of error as grounded in radical ignorance bypasses the need to appeal to irrationality in order to explain economic (and other) mistakes. (shrink)