Paradox Interactive is rather known for its games having incredible breadth and depth, and the deeply flavored historical romp that is Europa Universalis 4 is no exception. Running a successful nation requires much skill and expertise and, perhaps most of all: planning. To that end, players must be aware of what idea groups they have available to them when they are useful to take and what boons they will unlock as they invest monarch points into them.
Not all idea groups are created equally, with some granting very specific boons and some being more all-rounders that can benefit almost any nation; some are best taken at the early parts of the game, and some are useful no matter when they are taken. It is needless to say that a handful of these idea groups are considered to be of a much higher tier than the rest.
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Updated May 19, 2022 by Ryan Bamsey: Europa Universalis 4 receives updates pretty consistently, and the balance of power changes pretty drastically every now and then. We've taken another look at the Idea Groups in EU4 and made sure this article is still accurate.
12 Religious Ideas
Religious ideas can be a little situational depending on your location in the world, but they are crucial for any nation that decides to expand into a region populated with heathens or a nation that decides to change its religion.
This idea group also has some fringe benefits, including a nice +1 yearly prestige and the incredibly powerful Deus Vult idea, which grants nations permanent casus belli against heathens and heretics - a fantastic boon for any expansionist empire.
11 Quantity Ideas
If you find that you run out of manpower in every war you fight, this idea group could be the perfect fit for you. This idea group significantly boosts your manpower, giving you larger reserves and a higher recovery speed.
The biggest nations in the game won't really need to take this... but if they do, they'll find that they can do away with 'strategy' and throw wave after wave of willing men at their foes, crushing them with sheer numbers and might.
10 Humanist Ideas
Humanist is another great idea group for larger nations who intend to expand their borders even further, possibly even better than Religious if the nation doesn’t intend on a mid-game religion switch. The +25% religious unity and -2 national unrest are perfect for staving off even the worst threats of an uprising. Truly, this idea group is almost a must-have for players who like to play wide.
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The bonus for completing the entire idea group — a nice ten percent reduction in idea cost — makes Humanist ideas a fantastic early-game pick for most nations.
9 Trade Ideas
While this idea group is another group that has its usefulness hinging on location, Trade ideas are certainly adept at improving a nation’s ability to generate ducats. Everything about this idea group is based around improving a nation’s financial worth, and completing it grants a full three extra merchants, which will put that nation head and shoulders above nations that don’t take Trade ideas.
It’s a bit of a one-trick pony, but the efficiency with which it works makes this idea group an attractive idea to take at any stage of the game.
8 Government-Based Ideas
This idea group changes based on what type of government you have, so there is some variance in quality. That said, you can't really go wrong with the bonuses they provide. Most nations in the game have access to Aristocratic Ideas, which grant a neat reduction to Military technology costs and a whole new Diplomat.
Alternative idea groups include Divine for feudal theocracies, Indiginous for native tribes, and Plutocratic, reserved for republics. The latter is pretty great, as it enables some truly overpowered Policies and comes with bonuses to manpower and a free Merchant. It's a true all-rounder.
7 Quality Ideas
While some players lament this idea group’s less-than-useful split focus on the army and navy, with naval improvements often being maligned by many nations, Quality ideas remain a fantastic pick for any nation that expects to fight land battles.
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Simply put, the +10 percent combat ability for infantry, cavalry, and eventually artillery, makes this idea group very valuable — and doubly so for nations who foresee naval battles in their future, like England or Castile. The +5 percent discipline bonus received for completing the idea group is a lovely cherry on top, too.
6 Exploration Ideas
Exploration is a vital idea group to take for any nation that wishes to explore the colonization features, thanks to the idea ‘Quest for the New World,’ which allows the recruitment of explorers and conquistadors. This is especially important if you want to take advantage of the Leviathan DLC's colonization features.
Apart from colonization, though, Exploration is a great idea group for any nation hoping to expand overseas thanks to the +25 percent naval force limit modifier and the ability to fabricate claims in colonial nations.
5 Diplomatic Ideas
This idea group is extremely useful for basically any nation. Not only does it grant a great two extra diplomats, but it makes everything under the heading of diplomacy easier. Staving off coalitions with some improved relations? Quicker. Making allies with stronger nations? Easier. Want to break off a royal marriage? Simply done!
This idea group is even more important if you want to play within the Holy Roman Empire - improving relations and becoming friendly with the various elector nations is vital for success if you have your gaze on the throne itself. It can also help stave off an emperor's retribution to make friends with them before acting out within the empire's borders.
A nice boon from Diplomatic ideas is the +1 diplomatic relation, which is great for stacking up great allies or accruing a large number of vassals. Additionally, Diplomatic ideas enable some seriously good policies that improve diplomatic reputation even further.
4 Defensive Ideas
This idea group is one that many smaller nations should prioritize because of its ability to make its lands harder to traverse. With a bonus to enemy attrition and fort defense, this idea group is a great way to enable successful defensive strategies, such as hiding out behind powerful forts and descending on unsuspecting enemy armies.
One of the biggest boons that this idea group grants is the +15 percent army morale bonus, which is just great for making sure soldiers don’t flee if they roll badly during combat.
3 Influence Ideas
This idea group is almost crucial for players who wish to play with many vassals. Not only does it bring in more money from the aforementioned vassals, but it encourages taking more and more with bonuses to liberty desire reduction and diplomatic reputation. Additionally, there’s a +100 percent bonus to vassal force limit contribution, which will lead to massive armies even when most of a nation’s land is given to vassals.
The best of the best, however, is the 50 percent bonus to unjustified demands, which basically means you can demand more spoils after a war – this can equate to even more vassals in the long run, compounding the value of this idea group.
With the game's ever-increasing focus on vassals thanks to the governing capacity updates, this idea group becomes more and more attractive a choice.
2 Offensive Ideas
The biggest bonus that the Offensive Ideas group grants a nation is the automatic improvements to its generals and other army leaders, making the armies they lead that much more likely to succeed during battles. But, that is not all, as this idea group is an all-around fantastic idea group for a nation’s military might for some other benefits it grants.
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In addition to the great siege ability and discipline bonuses (which will shorten wars considerably thanks to quicker battles and shorter sieges), the army morale recovery bonus will make it so that a nation’s army bounces back from lost battles even quicker. Offensive ideas are almost mandatory for players who play… offensively.
1 Innovative Ideas
Innovative ideas are possibly the greatest ideas in the game, thanks to how applicable they are at any point. The third idea in the group grants a fantastic 10 percent reduction to technology costs for the rest of the game, and that is worth the price of admission alone. Between that and increased institution spread, a huge reduction in advisor costs, and a nice modifier to war exhaustion, this group is a great all-rounder.
This group also grants a host of fantastic policies that really accentuate the other idea groups taken. Of particular note is the policy granted by Innovative and Offensive ideas, which makes sieging a cinch.
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