Humans sometimes have phenomenal ability to keep doing the same thing over and over, even if it does not work. For example common people keep trying and trying the same dating methods that proven to not work. You can see that even among policy makers, who in theory supposed to know better. Yet despite being proven as unworkable over and over again, they keep trying the same solutions over and over again.
I am talking of course of trying to somehow reconcile two or several distinct people and somehow make them co-exist in the same common state. It never works. It did not work in Northern Ireland, in Lebanon, in Ethiopia, in Yugoslavia, in Bosnia and Kosovo after collapse of Yugoslavia, in Netherlands, in Belgium after Netherlands, in USSR, in pretty much all post-Soviet states and many more. Yet despite this consistent track record of failure, this same solution is offered to other people and places like Cyprus and Northern Sahara. Various UN mediators and members of global community keep offering various federal solutions that would get two sides with mutual hatred and irreconcilable differences to somehow work together, instead of doing the obvious and letting them split into two distinct states with reasonable border.
The only place where something like that ever worked is Switzerland. But Switzerland is but exception that only proves the rule. There are other things that do no work elsewhere, that somehow work in Switzerland only. Moreover if you actually look at Switzerland in detail, you will understand that it does not work even there. Sure Switzerland in multilingual but only on federal level. Most individual cantons are either monolingual or have a clearly dominant language. Thus there are no multilingual Swiss who live side by side no matter what their language is, instead there are clear internal borders that divide different languages from each other as well as different communities of the same language but other differences from each other. No one talks about acceptance there, instead they all know where each individual community begins and ends. An attempt to somehow erase these internal boundaries and make Switzerland into a unitary state was tried in early 19th century and was backed by Napoleon himself, but that collapsed within few years and federal divisions remain in place ever since.
Multiculturalism only works when either all people are migrants and no one has home advantage or when all minorities are no bigger than 5% and dispersed territorially so that they could not form ethnic enclaves with their own rules there or form a cohesive political party along ethnic or religious lines. That is how it is in most western states.
One post-Soviet state, Lithuania also falls into this category. Low rate or ethnic Russians in Lithuania prevents the dynamic that dominates society in neighboring Latvia and Estonia where native Estonians and Latvians are pitted against Latvian and Estonian Russians who have their own identity, culture, ethnic parties and even flag. That illustrates that these conflicts have nothing to do with any particular ethnicity, culture, location or religion but entirely due to relative sizes of the ethnicities. 5% could never elect to parliament their own equivalent of Tatyana Zhdanoka, who believes all ethnic Latvians are Nazis, but something like 10% or above can. The larger their relative rate, the worse animosity between them and the natives will be.
However lets also answer the question why all sort of bi-ethnic or bi-national states always devolve into their own version of Northern Ireland problem. To be completely precise, one may call them a 'finite number national' as say Yugoslavia who suffered from similar dynamic had 6 official ethnicities or nationalities and few more unofficial, one of which was larger than certain official ones. but its too long of a term so I will use bi-national instead. The point is to distinguish it from a kind of close to infinite number of cultures multicultural state, typical for western democracies, where foreign cultures are so many and dispersed, they are normally not counted separately or amount to an ethnicity or religion based autonomy/ghetto with their own de-jure or de-facto rules or power base.
So why multicultural states work and bi-cultural do not. Simple answer is the size. In a multicultural state each ethnicity is too small and/or dispersed to pose any meaningful threat to the majority. Thus locals mostly treat minorities with either curiosity or indifference. They may enrich their experience with their culture, cuisine or knowledge, but they could not form a power block of their own to challenge existing power structures. Even if they want power, they have no choice but to join existing institutions, political parties and such, boosting them instead of creating their own separate power bases that rival the existing ones. There they will have to appeal to locals and their sentiments to get somewhere. Through that gradually these people assimilate and even if they retain some of their original culture or identity, for the most part they become part of their new/host society. Their children would be even more integrated then they are, even if they married someone from their culture. Their grandchildren even more so. Gradually the multicultural society seamlessly absorbs such members, making them part of social fabric and enriching it even.
Those dynamics change however if any particular minority reaches either a certain size, I will say it's about 10% or achieves high concentration in a certain part of the country. It does not matter when they all are different as they will have more differences with each other compared to the majority. That changes dynamic. Instead of assimilating and integrating, the minority instead forms its own minority community based on ethnicity, language, culture or religion. From there on such community focuses on preserving their differences and identity. It becomes its own power based, focused on both self-preservation as distinct entity as well as advancement of their power and influence in a broader society.
The higher the number the worse the problem becomes. A 10% (of total population of a country) community will be able to preserve their distinct identity but will not be able to challenge the majority for control of society and will instead focus on growing their numbers and safeguarding their distinctiveness and power base. Meanwhile a 40% strong one might instead plot for a political takeover and then gradual replacement of the majority by their own members. A community might have a powerful foreign backer, like the state they originally came from or a foreign power, who seeks to undermine the state they are based in.
So, if you look closely at all the problem cases, they all have this close to even split in society. 60% Protestants and 40% Catholics in Northern Ireland. Same rate of Flemish and Walloons in Belgium or Latvians and Russians in Latvia. 50% of Russians in USSR or Serbs in Yugoslavia and the rest split between various minorities, some of which are rather large. 50% of Bosniaks in Bosnia. Less than 50% of any ethnicity in Ethiopia or Lebanon.
Such spit brings about the worst qualities and traits humans capable of. Tribalism, us vs them, pettiness, malice, cruelty and willingness to do the worst things imaginable. Both sides grow to see each other as existential threat and begin to focus on exterminating other ethnic groups instead of finding ways to live better together.
In bi-ethnic state politics devolve from based on socio-economic issues and policy debate into one based on ethnicity. At 10% rate politics not yet devolve into ethnic one, but a minority interest party may be present among the usual socio-economic ones. However at higher rate of minorities (around 20% to 30%), politics and political parties devolve to tribalism and people begin to vote for parties that represent their ethnicity and religion rather than economic interests. If you look at Northern Ireland, its impossible to distinguished various unionist parties based on their economic stances as this clearly takes back seat and essentially ignored over the overreaching issue of opposition to Catholics and preserving union with UK. In Bosnia or even Belgium its no different, parties do not have their ethnicities in their names but locals all know who represent which ethnicity.
This voting based on ethnicity compromises the very reason why democracy is such a workable system, that makes state responsive to its people. Ethnic parties are not created to represent needs and desires of the people, they are created as power vehicles for their ethnicities, to either gain or keep power in the hands of the ethnicity it represeents: keep us in charge and them out in plain terms. Such parties will not hesitate to make descisions that are detrimental to society as whole in order to shore up their grip on power. Over time this will make life miserable.
A society in such bi-ethno states are no better. Unlike outsiders who may say, why could not they all get along. Locals all know who is who and will almost certainly only cater to members of their own ethnicity while denying the same for other ethnicities. Even when in constitution and various laws discrimination is officially forbidden, the person in charge can still figure out how to deny something to an outsider, while lying about the real reasons for such denial. Petty spite, akin to a preverbal joke or person wishing to lose one leg so that his neighbor loses both, becomes a norm of life. Sometimes it comes to completely absurd situations where ethnically Serb acting mayor of Mostar deliberately sabotaged rubbish collection in the city for no other reason but to drawn local Croats and Bosniaks in rubbish, as they are by far outnumber Serbs in the city. It sound like a sick joke, but it actually happens in Mostar maybe even now. That makes even Northern Irish look sane in comparison.
However what drives this seamlessly insane behavior? Are they all stupid, these people in bi-ethnic states. Far from it. If it was an insanity it would not repeat itself over and over again under similar conditions all across the cultures, religions and continents.
The answer is survival instinct, a fundamental subconscious trait, present in human's psychology, that dates back to prehistoric times. Once the two ethnicities start to perceive each other as an existential threat, all gloves are off. They will stop at nothing to either completely destroy or neuter the other group. No amount of various peace agreements, power sharing deals or international monitoring could possibly stop the two groups from trying to completely obliterate their enemies. Both sides will go to the wits end to exploit and abuse the rules to damage the rival group as much as possible. If they can fight conventional war, they will. If they cannot they will still fight by other means, routinely misusing political and economic power to harm their enemies.
That is why Northern Irish unionists refuse to participate in government. Because it would allow their catholic republican enemies to be a First Minister, so they would rather have no government than let their enemies be in charge. That is why different ethnic groups in Bosnia routinely misuse Dayton Agreement provisions to harm each other, rather than share power and govern together as was the intention of Great Powers who sponsored it. List goes on.
This applies not just to politicians, but to common people too. The moment they see you are from a rival community, they will refuse to help, or hire and so on. Among other things, Catholics in Northern Ireland complained Protestants simply refuse to hire them for any good jobs the moment they know applicant is a Catholic. It no different in Bosnia or elsewhere where one ethnic identity decides who is allowed an who is not. Prohibitions against discrimination will do nothing as those in charge will make up some legal reason to deny job or help to their enemies. As much as a outsider might fight it difficult to tell two rivals apart, locals always know who is who and will treat people based on ethnicity.
To top it all up, if sides fought an active conflict. Then animosity grows many fold. No matter who started it and who is at fault, both sides will only see or care for their own casualties and grievances and will never forgive the other side who did this. Active conflict leads towards both sides dehumanising their opponents as some kind of inhuman beings unworthy of existence. For example both Russians and Ukrainians are now calling each others Nazis. Ukrainians cheer at each Russian death. And many Russians on X openly deny Ukrainians even a personhood or a say over their country fate, a rhetoric even worse that what actual Nazi use to say about Jews. Restoring relationship from that point is impossible.
Because of the above, the only solution to bi-national states as well as various ethnic conflicts is their split up into two or more independent states. All attempts to somehow reconcile the two sides and make them somehow co-exist together is but a fools errand that always lead towards misery or even quiet but complete extermination of one side by another.
Thus global peace efforts should focus not on reuniting places like Cyprus or Western Sahara but on an orderly and organised split up between the sides and mutual recognition of new borders. When people cannot coexist each other, its pointless to try and make them. One should instead help them split up and begin living separately from each other.
Yes, it will lead towards creation of new states and alter global maps, but its the only method that is both humane and ultimately workable. It will gradually lead towards more stability as new states will be much more safe and stable, because lack of any ethnic or religious split would eliminate most if not all grounds for civil and political strife, that might lead towards civil wars or events like Troubles in Northern Ireland.
All living cells multiply by dividing into two, this is a fundamental principle of life. By extension human societies grow and multiply by dividing into smaller groups and growing on their own. Trying to re-unite such societies would be going against natural order of things and nothing good will ever come from it.




