The reasons why historians disagree are many and varied, but the following represent some of them:
- Questions of the selection and relevance of evidence
- The method and the techniques of history
- Ideology and political predisposition
- The purpose for which history is studied in the first place
- More recently, arguments about the validity of historical method
At the level of primary research and evidence, historians often find different evidence on the same subject. In some areas of historical inquiry new information causes new conclusions to be drawn and that evidence as well as those conclusions is then contested.