And so ends the old order,

With Indyref fever full boil.

Lefties campaign for a border,

Greenies shout Yay for the oil.

—Rosie Bell

In May 2011—almost a year to the day after I moved to Edinburgh—the Scottish National Party (SNP) won a parliamentary majority in the Holyrood elections. This, of course, was supposed to be impossible. Scotland's electoral system—in place since devolution in 1998—was designed to prevent majorities.

That result meant a referendum on Scottish independence became inevitable, although it was clear that achieving a "yes" to independence was always going to be a struggle. Not only did many people vote SNP in 2011 because they were furious with Scotland's other political parties; thanks to the country's idiosyncratic electoral boundaries, the SNP won a majority of seats (53.49 percent) with a plurality of the popular vote (44.04 percent).

For a long time, this political reality was reflected in the polls: the "yes" vote lagged behind, often by as much as 20 percent. Both campaigns lacked energy, and debate was restrained. Commentary focussed on the civility of the Scottish people, and the lesson in citizenship the country was giving the world, without appreciating that the civility often had its roots in a lack of engagement.

My first inkling that the debate over "Indyref," as it is called in Scotland, was changing in tone was when, as a lawyer at a commercial law firm, the partners told my colleagues and me not to take a public stance on the vote. Potential clients were starting to choose their advisers based on which way the firm in question was perceived to lean on independence. At first I thought it was just my firm, but word filtered back to me from friends in other firms: they'd received the same instruction, too.

Soon after, the polls began to narrow. Indyref debates around the country—once merely well attended—filled to bursting point. There was violence in Glasgow. The numbers registering to vote rose to unprecedented levels. Turnout on September 18 may well exceed 85 percent. People have been warned of long lines at voting stations.

Last week, the polls crossed for the first time, with "yes" taking a narrow lead. At time of writing, the result remains too close to call. The British pound sank against the U.S. dollar on the news, while the London Stock Exchange developed a notable case of the jitters.

Both camps have prepared detailed manifestos—running to hundreds of pages—outlining their vision for Scotland's future. The "no" camp, recognising the popularity of devolution, has promised more local autonomy for Scotland, and it is difficult to see how—assuming "no" wins on Thursday—the U.K. will avoid a federal political settlement of some sort.

Meanwhile, the "yes" camp has run hard on the political differences between Scotland and England. The Conservative Party is weak in Scotland: The country turned its face decisively against the Tories in the wake of Thatcherism. For all that Thatcher's economic reforms benefited the U.K. as a whole—and they did, enormously—many Scots remember the decay of shipbuilding on the Clyde and the Poll Tax (introduced a year earlier in Scotland than in England). The latter led to widespread tax resistance and, sometimes, riots. "Yes" has spoken often of a kinder, gentler, more equal, more progressive country than is Scotland's large neighbour to the south.

At least in recent times, the political differences have been marked on a national level. Remove Scotland from the rest of the U.K. in the general elections of 1964, 1974, and 2010 and the result would have been decisive Conservative majorities. However, the 2014 European Parliament elections were a salutary reminder that Scotland is less different from England than it thinks: The anti-EU, anti-immigration UKIP also polled well. Indeed, the combined UKIP and Conservative vote was greater than Labour's, and only just behind the SNP's.

Indyref's true complexity is incapable of description here, but four issues remain central. They are, in no particular order: oil, E.U. membership, currency, and pensions.

The SNP campaigned over many years for a greater return of North Sea revenues to Scotland (91 percent falls into Scottish territorial waters). Recent scaremongering about the North Sea running out of oil and gas by the "no" camp fails to recognise that it is a basic economic truth that oil fields remain productive at the margins while oil prices remain high. That it is more difficult to recover the resource matters little when there is still money to be made.

However, the U.K.'s tax regime encourages exploration in difficult-to-access oilfields, meaning that no government—including that of an independent Scotland—can keep the rate of return on oil and gas revenues constant.

When it comes to E.U. membership, it seems that an independent Scotland would eventually accede, but eventually is the key word. Many E.U. member states require referendums in their own countries before the larger trading bloc can admit a new country, and no member state of the E.U. has previously broken up with the smaller bit then applying to join.

This leaves lawyers in Brussels not only rather short of precedents, but also with awareness that Spain has serious separatist movements of its own. Inspired by the Scots, the Catalans and Basques may make a run for it. Both "yes" and "no" have mishandled the E.U. membership issue, failing to understand the legal complexities and, in some cases, providing information that is simply wrong: at one point, "yes" falsely claimed that Scotland would automatically become an E.U. member.

Spooked by the ailing euro across the channel, the Labour and Conservative Parties alike have rejected currency union with an independent Scotland. Scotland's First Minister, Alex Salmond, says that England is bluffing, and he may be right, but it remains true that currency union without true political or fiscal union is economic nightmare fuel, something the slow-motion train wreck of the euro seems to evince at least once a week.

As an alternative to formal currency union, "yes" has proposed "sterlingisation," where Scotland—much as Panama does with the U.S. dollar—uses the pound without England's permission. This would leave an independent Scotland without a central bank or a lender of last resort. It would undermine the SNP's plans for a debt-fuelled, social democratic utopia: The austerity would be swift and severe, any socialism followed by an aggressive move to free markets and deregulation. However, it would also impose prudence on Scotland's banks and probity on the financial sector, insulating Scotland from nasties like the Global Financial Crisis.

While oil, E.U. membership, and currency have been central to the debate for some time now—the sheer scale of the pensions crisis, both as it applies to the U.K. as a whole and a putative independent Scotland—has only come to the fore as the polls have narrowed. Americans often expectorate about their country's social security black hole, but the U.K.'s is off the scale. The state pension is a genuine Ponzi scheme: Current revenues are paying for current entitlements, combined with an ever-growing pool of recipients.

Within the U.K., Scotland's position is worse: its population is both older and sicker than that of England and Wales. The crisis would bite sooner, with public sector net borrowing (what needs to be borrowed over and above tax revenues) rising from 4 percent this decade to around 10 percent by mid-century. In short order, public debt would rise to 200 percent of GDP—and, as one commentator put it this week, "that's a larger hole than the one Greece is in."

When I departed the U.K. to work in Australia, I deliberately left my Indyref polling card behind. I thought it improper to vote on the future of a country in which I no longer lived. The wisdom of my decision was brought home to me while writing this piece. Were I still practising corporate law in Edinburgh, I would vote "no." Concerns for my future as a lawyer and the viability of Scottish companies would trump any desire to see something of an uncontrolled experiment with sterlingisation.

From afar, though, I hope "yes" wins the day, because I also think Scotland's robust civic culture would make a fair fist of independence. The socialism would evaporate, sure, but the country would not fall prey to the "resource curse" so common among small, oil-rich nations. That Scotland gifted the world the skeptical Enlightenment would stand it in good stead. Its current inhabitants may prove themselves worthy heirs to Adam Smith, David Hume, and all the rest.

Very glad I left that polling card behind.