Early 20th-century Prime Minister Arthur Balfour is credited with saying history doesn't repeat itself, historians merely repeat one another.
It was a clever aphorism, albeit one that underplayed the cyclical nature of many political issues. The current discussion about British membership of the EU, for example, first took place in 1973-75, while the debate over Scottish independence is an echo of that concerning Ireland more than a century ago.
I don't just mean the broad outline of each debate, often the detail, rhetoric and discourse are remarkably similar, something brought vividly to life by Charles Townshend's recent book The Republic which charts the Irish fight for independence between 1918-23. He touches upon the Government of Ireland Act 1914, a little mourned piece of legislation that this year marks its centenary, Westminster's third - and nearly successful - attempt to create a devolved legislature in Dublin.
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Of course it was too little too late, a measure put on hold by the First World War and overtaken by events by the time hostilities ceased four years later, but nevertheless it remains a great what-if of 20th century British history. Amid a detailed catalogue of the violence perpetrated by both sides - mercifully something with no Scottish equivalent - Townshend charts the contours of Irish nationalism during a period of incredible constitutional flux.
While Sinn Fein talked the language of republicanism, many of its strategists privately accepted outright independence for Ireland neither enjoyed public support nor was likely to be granted by London. Eventually, Eamon de Valera settled upon the idea of "external association", an imaginative attempt to win the maximum possible sovereignty for Ireland within the then British Empire. Little separated that from the Dominion status favoured by ministers in London, thus a deal - the 1921 British-Irish Treaty - was possible.
Meanwhile, there were lengthy debates about whether Ireland was subsidised, currency and who should be head of state (the Salmond-like Arthur Griffith proposed a British-Irish "dual monarchy"), all familiar territory for the student of constitutional politics in 2014.
As another historian, Linda Colley, recently observed, the 1914 Government of Ireland Act also stands as a reminder alternative visions of the UK - not just Ireland or Scotland - are nothing new. Many Liberals envisaged devolution for Ireland as the first step in a wider process of "Home Rule all round", a UK federation in all but name.
Thus 1914 could also be seen as the high watermark of British federalism, a radical vision of a decentralised UK as the nexus of a worldwide empire (even the SNP, upon its founding in 1934, found the concept of Imperial Federation appealing). Colley clearly thinks this is something contemporary politicians ought to be studying more closely, and indeed there are signs more imaginative members of the Scottish Labour Party have been doing exactly that: just yesterday former Glasgow City Council leader Steven Purcell declared his support for a federal approach, complete with an English parliament.
Last week, meanwhile, former First Minister Henry McLeish urged his party to articulate a "modern, looser, flexible, federal" United Kingdom, while Jim Gallagher, recently unveiled as Better Together's new strategist, has also deployed the "f" word in his refreshingly thoughtful analysis of potential constitutional change.
Writing last September, he set out his ideal "union state", one that retained a combination of "economic integration and social solidarity". He continued: "Subject to that, it should be home rule all round and, as in federal countries worldwide, national parliaments should be funded by a mixture of a share of UK taxes."
A recent speech by Gordon Brown echoed this analysis reasonably closely.
Obviously this remains vague, but it still demonstrates the Scottish Labour Party isn't a spent force when it comes to constitutional reform (last year's interim report on further devolution remains a cogent and under-rated document). Alas, a few supportive remarks do not a federalist programme make, and it would be foolish to pretend Unionists are on the cusp of revisiting the spirit of 1914.
Yet I'm often puzzled at how intolerant certain public figures are when it comes to federalist chatter. I've been told off by shadow cabinet ministers for raising it and admonished privately by fellow commentators and publicly via Twitter. It's never going to happen they say. Curiously, the most dismissive are often supporters of devo-max or independence, both outcomes that would have been considered unrealistic 10 or 20 years ago, as indeed was devolution half a century earlier.
It is essentially a conservative argument, yet the leap from the present quasi-federal arrangement to a proper one (with a written constitution) is much shorter and arguably involves fewer intellectual contortions than the posited jump from the status quo to "independence-lite". Indeed, it would codify the unspoken consensus between the Yes and No camps that some things are best left to London and others Edinburgh, while satisfying the majority of Scots who desire neither independence nor no change.
Yes Scotland strategist Stephen Noon has acknowledged federalism would "give people in Scotland a great deal of what we want" (before slipping into the standard caveat about it being "out of reach", while Mr Salmond suggested federalists' timing "was slightly late". Yet, federalism arguably enjoys wider political support than independence. David Melding, the (Conservative) Deputy Presiding Officer of the Welsh Assembly, has made a lucid federalist case in several publications (endorsed by many Scottish Tories); the Scottish Liberal Democrats rebooted their federalist credentials last year, while even Nigel Farage talks of "a vibrant Scotland within a federal independent Britain".
All that can safely be claimed is there is something discernible taking shape in the undergrowth of the constitutional debate, a belated acknowledgement that what might be called the unfinished business of Blair-era constitutional reforms has to be acknowledged and, more to the point, addressed. But as Mr McLeish also wrote last week, that case has to be made now "with conviction and enthusiasm", for it makes little sense "to wait until 2015".
Alas, history tells us objectively sensible constitutional reform is often kicked into the long grass. Proponents of an elected House of Lords need look no further than the preamble to the 1911 Parliament Act for proof procrastination is almost a feature of the uncodified UK constitution, yet the case is there to be made. As Yeats wrote in the wake of the First World War, gloomily but perceptively: "The best lack all conviction, while the worst are full of passionate intensity."