in my world there is a country that has 2 two branches of centralized government. The first is a king who inherits power from the previous ruler, then there's a council of priests who are elected for life by the nation at Large. Traditionally the King has the authority to make laws while the Theocratic Council can veto any decision of government that violates religious principles or teachings with unanimous vote of all 12 members. they can also pass some some laws concerning religious and spiritual matters. my question is how can I maintain this status quo. in the case of a disagreement how do I prevent the king from dissolving the Theocratic Council and how do I prevent the Theocratic Council from turning the king into a puppet ruler?
This resembles what we know of ancient Sumer
To generalize about Sumerian society, the King (or Lugal, which translates as 'big man') held a hereditary position at the head of the city-state, and each city-state itself was centered on its temple. The gods of ancient Mesopotamia were each originally city gods, and as the various cities rose to prominence, their gods rose with them.
For example, prominent gods included Enki god of both Eridu and Abzu the freshwater ocean under the Earth. Eridu, which was mythologically the first city in the world and archaeologically attested by 5400 BC, was very old even for Sumer. Anu of Uruk was the sky-father, and father of the gods. Uruk was probably the largest city in the world from 3000-2000 BC, with up to 80,000 people in a 6 km$^2$ walled city. Enlil and Ninlin, brother and sister, husband and wife, were gods of Storms and Winds, respectively and lived in Nippur. Nippur was considered the 'holy city' from Sumerian into Akkadian times, and many rulers fought to control it to enhance their prestige.
The ruler's roles are defined in relation to the city-god
The relation between the city and its god is of paramount importance to the people of the city. This is the backbone of the power-sharing between priest and King. The king is...well...king and has all the secular power in the state, along with a monopoly on violence. He runs the army and the courts, and is owed taxes by the non-priests. That represents his power base.
The priests, on the other hand, control much of the arable land. This can be particularly true in river valley civilizations where irrigated land is small in area but very fertile. Egypt was similar and the Indus valley may have been as well. So the priests control most of the arable land and also the people's devotion. The city-god is irrevocably tied to the life of the city, and the citizens simply believe that if the city-god is disrespected that the city will be abandoned and fall.
The citizens follow their god
The citizens of the city demand protection above all else. If they king respects the gods and provides protection, they are satisfied, and he can rule as he sees fit. If the king feuds with the priests and disrespects the gods, then the citizens will grumble. Why would soldiers go into battle with their god unhappy, knowing that their god must be at their side to gain victory? Why would serfs stay in the fields of a city whose own priests say has been abandoned by the gods? Religious sentiment is powerful, and the king must heed it. For it is through the power and might of Enlil, or Utu, or Tammuz or Sin that the King reigns, not his own.
Precedent and perhaps a Constitution
If the people generally believe that the king should stay out of religious matters and that the priests should stay out of secular politics, it would be hard for them to go against ingrained public opinion. "Render unto Caesar" and all that.
Both sides must have a stable power base and there must be clarity who owns what. Perhaps the church gets a tithe of a tenth of all food, while the king is allowed to tax artisans and merchants.
TL;DR Make both parties important in the eye of the public, then weave a web of checks and balances
"The faith and the crown are the two pillars that hold up this world. One collapses, so does the other." - Cersei Lannister, Game of Thrones
The above idealogy may actually suit your purposes well. If either party tries to take full control, the other has the legal power, backed by the public, to limit that attempt.
Elaboration on how this would work is below:
The King commands the kingdom's resources
In order to prevent a "king is puppet" scenario, the king must be able to hold his position, economically, physically, and politically - which can be done by giving him most of the actual, physical power. This will leave his branch responsible for regulating most of the government, as well as policing the population and executing punishment.
The Council commands the judicial system and preaches to the public
The gods always take precedent over the king when morals are in question, so as long as the council accurately communicates the wishes of the gods, they control the kingdom's courts. To prevent the dissipation of the council, the priests can argue, rightly so, that that would oppose the wishes of the gods, and strengthen the monarchical "pillar".
The military answers to the king, but is sworn under oath to follow the system described below.
A disagreement appears!
The kings' wishes are second to those of the gods, so the council will decide the outcome of these circumstances. One of three scenarios unfolds:
- A) Both parties accept the outcome. Therefore, the measures pass uneventfully.
- B) The king is refuses to accept defeat. He believes the councilors are not corrupt, but they believe he is. The council votes on whether the king has a reasonable cause to disagree (economics, wellbeing of the crown, etc).
- If the council believes the king is corrupt after further analysis, they give him one more chance. Upon the second unwarranted disagreement, he is dethroned by the general, who answers to the gods before the king, and replaced by a successor.
- If the council believes the king is not corrupt after further analysis, a further discussion ensues until a unanimous decision is reached; if the council is still not cohesive, they are replaced by a new set of councilors produced by a revote so that the government can maintain itself.
- C) The king refuses to accept defeat. He believes the councilors are corrupt, but they do not believe he is. His advisers (changed yearly) analyze the situation in depth.
- If no corruption is found, the council enacts the changes they wish to see.
- If the council is found to be corrupt, the public re-elects a new group of councilors. Innocent individuals will be pardoned, and guilty will be tried for treason against the king and the wishes of the gods, with the king's advisers replacing councilors as jurors. If the king re-shuffles the council more than twice in his reign, the law will see him replaced, and the general, sworn under oath to the gods, will see that the change takes place.
- D) Both parties believe the other is corrupt, so the government is not cohesive. Both B) and C) are attempted. If both are seen as corrupt, the councilors are replaced, but no parties are punished. If the second council reaches the same conclusions as the first, the king is replaced in the line of succession; if no heir is present, his advisers rule. The first council then takes over from the second, under the assumption it was unfairly discarded.