This paper investigates a solution to yes/no question answering, which can be mapped to the task of determining the correctness of a given proposition. Generally it is hard to obtain explicit evidence to conclude a proposition is false from an information source, so we convert this task to a set of factoid-style questions and use an existing question answering system as a subsystem. By aggregating the answers and confidence values from a factoid-style question answering system we can determine the correctness of the entire proposition or the substitutions that make the proposition false. We evaluated the system on multiple-choice questions from a university admission test on world history, and found it to be highly accurate. © 2012 The COLING.