When to capture enemy's capital?

[elmenhorster]

i mean when civilization splits in two separate civs after their capital falls, but not every time.. so what are the causes for that to happen? government?

 

[Prof. Garfield]

A civilization can split if there is at least 1 empty colour for the "rebel" faction to take. Moreover, civil wars are most likely to happen (or possibly only happen, I'm not sure) if the civ that captures the capital has a lower power rating than the civ that is going to be split.