Causes

Firaxis could make it a victorycondition.

Have a democratic nation a long time and you could select your 'cause' to be 'Liberation' and free other civs by making them democratic civs, either to liberate enough civ to win or just to get to their oil . Either way it doesn't matter since it politics.

'Free trade' could be a Capitalistic 'cause' which would antagonize some Communistic/socialistic 'cause' in the idealistic branch.

Different religions would have their own causes, perhaps starting as early the middle ages through the Crusades and Jihads but otherwise the 'cause'-concept probably would fit best in the modern era in which it could be seen upon as politics rather than absolute causes.

Anyway I like the 'Cause'-concept, it could give civ some more meaning than just expand and conquer, and give the modern era a boost.

Any more suggestions to the concept?

Doesnt sound promising. These causes are all essentially excuses to go to war, and beyond giving an in-game excuse for war (as if players need that), adds very little.

I like the idea and would like to expand on it.

Instead of conquoring another Civ, perhaps you could "liberate" them. By "liberating" you would not gain control of the cities, but the Civ would now be a puppet state that follows your Civ in politics. If you go to war they join in, if you ally with another Civ, they ally. They won't trade with another Civ without prompting you first. Units can share the same tiles (stack)

Not conquoring them may be more preferable if expantion would only cause more corruption.

The Liberation concept would fit in nicely with different 'Causes' and I'd like to see it implemented, but it's a new concept of itself.

The 'Cause'-concept would have something to add. At a higher level it would add direction to the game especially in the modern era.
If Firaxis listens to the critique regarding the too onedimensional gameplay which often leads to a boring endgame, they will make you rely more on politics, relations and negotiations to form alliances, unions and puppetstates.
In the realworld nations use causes to justify their actions, they might win their own populations support, especially if they're successful, but lose foreign support if they don't share the same cause.
Plus it might be a easy way to simulate the division there is and has been in world. The Cold War was fought over ideals, officially atleast, so why not introduce a concept that could divide the world politically in ideals, and let the player decide on either how to benefit from the situation or roleplay a civ fighting for it's ideals.
The same concept could be used to simulate religious wars without that much controversy, since the concept could be seen as having a political base (base to manipulate the population) - a greyzone, in contrast to dividing the world directly in specific ideals and religions.

Its a pretty simple concept that would be able to divide the world in several layers within the concept.

To select a 'Cause' you would have to achieve some goal before, perhaps in a 'Cause'-tree. Having traded with a number of civs for a long time while being democratic could for example let you select the 'Capitalistic Cause' which would make your reputation suffer with the Communistic civs, but improve the reputation with the democratic civs. Other stuff could of course also happen, a 'Free Trade'-cause/improvement/tech could be unlocked while having a 'Capitalistic Cause'. Some 'Causes' should of course be mutually exclusive.

To put it simple - The 'Cause' would be a uniting/dividing, driving force for the civs, particulary in the modern era, or just an excuse to justify another not-so-glorious goal, based on their 'culture' in the past.

These 'Causes' could be a form of minor, somewhat choosable traits, possibly traits that wear off after some event or a certain amount of time.

Say you're the most powerful civ in the world and you repeatedly suffer from terrordeeds through espionage missions of minor civs of different views/ideals/religions. After you've been attacked a number of times, you gain the ability to choose the 'Cause' - 'War on Terror', which could lower the warweariness in your own civ from attacking civs of other views/ideals/religions and perhaps that war would be less controversal in civs with similar views/ideals/religions, or make it easier to sign alliances.

Maybe fulfilling your cause (or at least making progress towards it) should count for victory points. COnversley, flubbing it when you've chanmpioned a cause should cost you some score.

That seems like a nice idea, better than making it a victorycondition that I first thought. Remembers me of Medieval: Total War that you could play for victorypoints, you were given a high number of points for building a citadel in Tripoli before a certain date for example. I thought it was a fun feature in that game.
I don't know if they kept it in Rome:Total War though.