By upgrading the Inquisitor's level, they receive Doctrine points. Use these to develop the Inquisitor. Upgrading Doctrines will enhance the Inquisitor and give you military and economic bonuses.

A Doctrine will start providing its bonuses as soon as you have spent at least one point on its development. The icons of any active Doctrines are in color, while inactive ones are gray. To redistribute Doctrine points, use the Purge item. This can be found in the Item Store and Order Store.