Apply corrections to an ingested corpus

An approach is provided to correct documents ingested by a question answering (QA) system. A document previously ingested by the QA system is selected. A correction to the selected document is identified from one or more correction sources and the correction is applied to the selected document within the QA system. In one embodiment, the correction source is a non-ingested document, such as a published document or an issued correction. In another embodiment, the correction source is a post in a forum. In this embodiment, a statement in the ingested document is compared with a contradictory statement found in an ingested post of a threaded discussion. The statement and the contradictory statement are evaluated by the QA system. The statement in the ingested document is replaced with the contradictory statement in response to the evaluation revealing that the contradictory statement is correct and that the statement is incorrect.