Many authors have argued that we should make a clear conceptual distinction between mononational and multinational states. Yet the number of empirical examples they refer to is rather limited. France or Germany are usually seen as mononational, whereas Belgium, Canada, Spain and the UK are considered multinational. How should we classify other cases? Here we can distinguish between (at least) two approaches in the literature: statistical (i.e., whether significant national minorities live within a larger state and, especially, whether they claim self-government) and subjective (i.e., when citizens feel allegiance to sub-state national identities). Neither of them, however, helps us to resolve the problem. Is Italy multinational (because it contains a German-speaking minority)? Is Germany really mononational (in spite of the official recognition of the Danes and the Sorbs in some Länder)? On the other hand, is Switzerland the “most multinational country” (Kymlicka)? Let us assume that there is no definite answer to this dilemma and that it is all a matter of degree. There are probably few (if any) clearly mononational states and few (if any) clearly multinational states. Should we abandon this distinction in favour of other concepts like “plurinationalism” (Keating), “nations-within-nations” (Miller), “postnational state” (Abizadeh, Habermas), or “post-sovereign state” (MacCormick)? The article discusses these issues and, in conclusion, addresses the problem of stability and shared identity “plural” societies.