The wisdom of the crowds is the thesis that if you ask sufficient people a question then even if each is individually not very knowledgable, the consensus view is remarkably accurate. This seems to work for certain kinds of problem where no expert knowledge is required, but if, say, the question concerned quantum string theory, it seems less lilely that a random crowd would be helpful unless it happend to be a crowd of quantum string theorists. However, a computational variant of this principle does seem to work well in ensemble methods in AI.
Used in Chap. 16: page 247