Political boundaries don’t always align with groupings of language and culture, and they can be changed. Most, if not all, countries contain several ethnic groups or ‘peoples’, with distinctive cultural identities, who can live together in peaceful pluralism (4.4.1) – but sometimes separatist or ‘nationalist’ pressures emerge.
Kwame Anthony Appia identified the challenge of holding a country together in his 2016 Reith lecture: 
“What makes “us” a people, ultimately, is a commitment to governing a common life together.
The challenge this poses for liberal democracies is formidable. Liberal states depend upon a civic creed that’s both potent and lean—potent enough to give significance to citizenship, lean enough to be shared by people with different religious and ethnic affiliations.”
Appia’s emphasis on the word together implied a sense of shared values, and identifying with the country as a whole. He argued that
“the truth of every modern nation is that political unity is never underwritten by some pre-existing national commonality. What binds citizens together is a commitment… to sharing the life of a modern state, united by its institutions, procedures, and precepts.”
People feel a sense of kinship to others within their cultural group. If they have reason to be dissatisfied with the government of the country, the value of citizenship is diminished and they are more ready to listen to someone who offers to assert their cultural identity and break away.
Breaking away, to form a separate State, can seem attractive – particularly if it is romanticised. Ernest Renan, in asking What is a nation?, expressed a romantic view in 1882: “A nation is a soul, a spiritual principle”. He argued that ‘nations’ should be defined by people’s desire to connect with their ancestors and “the clearly expressed desire to continue a common life” – although he did not address the difference between ‘nations’ and politically-administered States.
Nationalist politicians can use the techniques of the ‘alt-right’, as described earlier (22.214.171.124), to mobilise people’s sense of cultural identity and rally support for a separatist cause – despite the damage to peace and security that results from ethnic divisiveness (126.96.36.199).
The key issue, in a political negotiation, is to identify what aspects of governance the separatists want control over. It may be possible to devolve control over education and some economic matters, for example, without totally dismantling existing political structures.
Some groups may break the law – using terrorism, possibly escalating to civil war – in an attempt to reset the basis of negotiation. Civil war, which is a subject for the next chapter (7.2.6), can only be resolved by returning to the negotiating table to find a political solution.
There are several ways of politically accommodating a degree of separation between different cultural groups within a country, as described in the following sub-sections:
- Tribalism is a traditional form of fragmented governance with shifting borders (188.8.131.52).
- A federal structure or regionalisation, allowing a high degree of political autonomy, has been successful in several countries (184.108.40.206).
- Secession, resulting in partition, is the most extreme form of separatism; it has often been very painful (220.127.116.11).
- Within a society, separatist enclaves and ghettos can be allowed, or be encouraged, to develop (18.104.22.168).
 The quoted passage comes from page 8 of the PDF file of the text of Appiah’s 2016 Reith lecture, entitled “Country“, which was available in January 2018 at http://downloads.bbc.co.uk/radio4/transcripts/2016_reith2_Appiah_Mistaken_Identities_Country.pdf. .