The purpose of the co-supervisor is to contribute with competence, approaches and input that can complement what the main supervisor can offer. The co-supervisor typically reads the dissertation with specific goals in mind, is not responsible for assessing the dissertation as a whole (this is the main supervisor's responsibility) and will be consulted somewhat less frequently than the main supervisor.
When the candidate, in collaboration with the main supervisor, is looking for a secondary supervisor, you may have one or more of the following in mind:
- Competence in theory and / or methods that the candidate wants to use, and which the main supervisor does not work much with
- Language competence (eg if the dissertation is about Turkish cultural history and the main supervisor is a cultural historian without Turkish competence)
- Especially good empirical knowledge and personal network in a geographical area, in cases where the thesis has an area study component