The extent of Labour's defeat will have come as a bombshell.

Privately, Labour insiders were hopeful of retaining more than 10 seats in Scotland. The enormous swing to the SNP wouldn't be uniform. Incumbency and "shy Unionist" tactical voters would save some of their best people. In the event, the roaring Scottish lion blew them all away.

Having featured heavily in the election campaign, Scotland is prominent in the aftermath too. The Labour Party, English people generally and especially English politicians just don't "get" Scotland. Nicola Sturgeon has warned David Cameron that he "cannot ignore what has happened". But what has happened? What does the roar of the lion mean?

On the question of independence, Scotland voted No by a good margin in September. Last Thursday, Scotland elected 56 MPs from a party for which full independence is the raison d'etre. At the same time, Ms Sturgeon has explicitly said the Westminster election of 2015 provides no mandate for a second referendum and, according to the latest opinion polls (whatever they are now worth), the "no to independence" vote remains in the ascendency.

The left of the Labour Party points to Scotland as firm evidence that it should abandon the centre ground, yet the SNP manifesto essentially matched Labour's proposed tax increases and spending plans. On devolved taxation, the SNP put full fiscal responsibility before the electorate and many Scots voted for it. Today, the SNP backs away from the idea because of the huge deficit it would create.

Is it any wonder that some people are finding all of this hard to understand? Ah, these are mere details, I hear you say, ultimately irrelevant in the face of the great tidal movements of history that sweep peoples to independence.

It's a truism that, when emotion meets detail in politics, emotion wins out, which is key to understanding nationalism's purchase. It's an empty political vessel, ideologically neutral, ready to be filled with content from any part of the political spectrum. It thrives, though, on a burning sense of injustice, a belief that the natural order of things has been defied. This helps to explain why de-colonisation occurred in the 1960s as a cascade, not grounded on pragmatic arguments about the economic or political viability of the nation-state, but on a complete collapse in the legitimacy of empires and the glaring inequity of a racialised division of power.

But Scotland is not under imperial tutelage. This is not an anti-colonial moment. The idea that Scotland is oppressed within the Union is convincing only to a small minority of Scottish people. And far from being the "failed state" Tom Devine claimed it to be during the referendum campaign, the United Kingdom is a liberal polity evidently capable of reform: witness the whole project of devolution since 1997. The scope for the British state to devolve further powers to Scotland is still large, and the willingness to do so palpable across Westminster.

Oh well, this all just makes independence inevitable. This view is being expressed across Scotland and England too, where many have grown impatient with the "Scottish problem" and arguments for why the Union ought to survive seem far from compelling.

Therein lies the problem. When Scotland revisits the independence question, economic details will return to the fore, but they will not be sufficient. If emotion and rhetoric are governing forces in politics, and the narrative of inevitable independence goes unchallenged, it may come to appear self-evident and thus become self-fulfilling.

So what is the normative case for the Union in the 21st century? It's essentially a liberal one. It says that cooperation, the sharing of resources and pooling of sovereignty are a better state of affairs than a recidivist nationalism that seeks to reconstruct a 19th century world of imagined divisions and invented barriers in Europe.

Ideologically, the modern case for the Union is actually very similar to the one for the EU, and as the EU referendum approaches, it will be interesting to see the SNP denounce the Tory right's arguments for self-determination. Sooner or later the SNP's contradictions will catch up with them.

Dr Collins is a Lecturer in British History in the Department of History, and the Director for Democracy and Institutional Change at the Global Governance Institute, University College London.