Unless the system has been changed since the Diplomacy version, doctrines are tied to specific regular researches. You unlock the tied research and the corresponding doctrine unlocks.
It usually gives an additional global bonus with the same theme as the tied regular research. Also, unless changed since the Diplomacy mod version, you can research all doctrines once they have been unlocked, you do not have to pick between them.
I think you should explain this one a little bit more. Looks very interesting.
can you reseach all of them?
Unless the system has been changed since the Diplomacy version, doctrines are tied to specific regular researches. You unlock the tied research and the corresponding doctrine unlocks.
It usually gives an additional global bonus with the same theme as the tied regular research. Also, unless changed since the Diplomacy mod version, you can research all doctrines once they have been unlocked, you do not have to pick between them.