[comisar]

Well , I have played Europa-Universalis for more then a year one. I have modded it quite a lot in EU and I know a whole lot about it. I am new to SEIV, but both games are very similar, very detailed, deep and stategic with global scope.
I have to say that the diplomacy in SEIV from what I have seen so far is really lucking.
In addition to what Barnacle Bill mentions EU also holds a "Bad Boy" rating for each nation (there can be 200+ nations is any one time) That value increases as your empire become bigger and bigger, it will really jump if you competely take over another nation) If you bad boy value is the highest in a game you can eventually be expeced to be attacked by everyone! That value only decrases with time, so unless you want to fight everyone at once you have to control your aggresion.
If addition to bad boy there is stability setting. It goes from -3 to 3. Stability effects revolt risks, productuctivity and things like that. If you attack a nation without a cause your stability goes down. If you break an allience or any other aggrement with another nation it goes down. If you declare war on a nation with whom you have good relations with or nation that pays you tribute (vassal) stability goes down a lot. If you attack some nation with same religion as you the stability goes down. And stability of -3 is bad as you are not as productive and have to fight rebellions all the time + rebelious provinces do not pay taxes or give you any income.
Stability increases with time.
So what is a cause to war? For example if your ally get attacked you can choose not to help out but the ally with get a cause to go to war with you. There are many other things that are considered a cause to war, like you can state that you are protecting nation X and if anyone attacks that nation you have a cause of war againt that country, you can also claim to be defender of your religion and if any nation attacks a nation with your religius you get causes to war against them, etc.