The concept of Galactic Unity was founded on five basic principles: Monolithic Obedience, Destruction of Individuality, Totalitarian Rule, One Structure, and Combine Domination.
The first, Monolithic Obedience, refers to the Combine's doctrine for complete obedience to the system.
The second, Destruction of Individuality, refers to the Combine's emphasis on collective, not the self.
The third, Totalitarian Rule, refers to the Overseers. They rule for their whole lives, holding all the power in their small group.
The fourth, One Structure, refers to one political, societal, and economical structure only, within and without the Combine Empire. Anyone within who refuses to merge with the system is purged, any outsiders foolish to resist assimilation is exterminated.
The fifth and final one, Combine Domination, refers to the eventual goal for the Combine Empire: Complete and utter domination of the universe.
Overseer 3, the oldest Combine Overseer currently, created the ideology for the Combine Empire soon after the Empire's founding. His ideas were quickly accepted in by the Combine's Overseer Council.
The original Combine ideology favored tolerance of other ideologies and powers, as the Founder, Overseer 1, wanted to be in good relations with the other neighboring powers of the galaxy. However, upon seeing the new doctrine created by Overseer 3, the majority of the Overseer Council voted for Galactic Unity. Overseer 1 gave his ultimate blessing as well, enabling the new doctrine to become the ultimate ideology of the Combine.