In the campaigns to capture the hearts and minds of Scots ahead of next week's independence referendum, much talk has swirled around everything from the fate of lucrative offshore oil and gas revenues to feelings about being governed by politicians in distant London.

But some issues have taken on greater significance in the run-up to the Sept. 18 referendum, which could end the 307-year union within the United Kingdom.

"By far the most effective campaign tools for knocking people from undecided into one of the two camps, and particularly in terms of compelling Yes support, have been the economy and currency on the one hand and Europe on the other and the implied threat of spending cuts," says Ailsa Henderson, a Windsor, Ont., native who is head of politics and international relations at the University of Edinburgh.

"That's been a very effective message."

Scotland independence vote

Experts say some of the most effective campaign tools for compelling Yes support have been the economy, currency, Europe and the implied threat of spending cuts. (Jeff J Mitchell/Getty)

Henderson, who is not associated with either side, can quickly rattle off a list of likely predictors for voting Yes.

"It's liking [head of the Yes side] Alex Salmond, it's feeling certain about the consequence of independence, whether you are correctly or not is another issue, but feeling certain … that you're going to get to use the pound, being absolutely convinced that you're going to get into [the European Union] and worrying that spending cuts are coming if you remain within the U.K."

For the No side, Henderson says it's the exact opposite.

Here are the four issues that may sway the debate.

1. Currency

One touchstone has been the British pound, and what currency an independent Scotland would use.

The Yes side is "saying that what they would like is to use the pound in a currency union, and if the U.K. government doesn't agree to the currency union, they'll use the pound anyway," says Henderson, the author of Hierarchies of Belonging: National Identity and Political Culture in Scotland and Quebec.

"The U.K. government points out that if you're using the pound without a currency union, you've got absolutely no influence over the levers of your own economy, so that's a tricky move."

Mark Carney, the Canadian-born governor of the Bank of England, has also waded into the issue, and said Scottish independence is "incompatible" with retaining the pound.

Frank Muller, a professor in the school of history at University of St. Andrews who is on the No side, says a currency union with the U.K. is "unlikely to be offered and — if it were offered — would be unlikely to work successfully — both economically and politically."

"I am therefore entirely at a loss as to how Scotland's currency question would be resolved in a solid, relatively shock-proof way," he wrote in an email.

But Steve Murdoch, another history professor at St. Andrews but on the Yes side, is less concerned about the pound and says there are countries that use currencies other than their own.

"I don't see that as problematic, whichever currency solution we use, whether it's the euro or whether it's the pound or whether it's a separate currency," he says, emphasizing, however, that he's not an economist.

2. Oil and gas revenues and the economy

Henderson says there are two issues wound up in the discussion around revenues from North Sea oil and gas.

"One is about how much oil is left and how long it can sustain Scotland, and then the other issue, of course, is how victim would we be to the changing price of oil."

Britain Scotland Referendum

Controlling a greater share of North Sea oil revenue is a key plank in Scottish First Minister Alex Salmond's Yes campaign, but many are questioning the accuracy of oil and gas data. (Andrew Milligan/Associated Press)

There are no clear answers to those questions, although many numbers reaching into the billions have been thrust around in the debate.

"We're getting wildly different expectations or wildly different predictions from different sides about how much oil is left, as well as wildly different predictions about how much oil will be worth," says Henderson.

Muller says he dislikes the idea that oil and gas belongs to "us Scots" and should not be shared in a wider community.

"Why should oil/gas revenues from the North Sea benefit a poor child in Stranraer and not a poor child in Newcastle? It is my rejection of the collective selfishness of nationalism that guides me here."

He says he is also concerned about "the proportionally much larger role this volatile and finite income stream would play in the financing of essential public services in an independent Scotland. The much larger, much more diverse U.K. income base offers a safer alternative."

Murdoch says there's no doubt games have been played with oil and gas data. He'd like to see more emphasis on renewable energy. He also thinks Scotland has other economic options.

"We've got other industries which are multi-billion-pound industries such as the whisky industry, but we've also got good farming, good fishing and I think that we can sustain ourselves without overemphasizing the oil revenue."

3. European Union membership

Whether an independent Scotland would be able to join the European Union has also become a focal point in the debate.

Among academic lawyers not attached to either side, a consensus seems to be emerging that Scotland would probably be able to get into the European Union, but the terms of membership would be "nowhere near as favourable as they are just now," says Henderson.

The referendum camps are firmly divided on the question.

"Yes are saying 'absolutely they'll let us in' and No are saying 'absolutely they won't,'" says Henderson.

Muller thinks the question of EU membership is important.

"Re-entering the EU would, in my opinion, be a lengthy, disruptive process," he says.

On the Yes side, Murdoch says he's "delighted to be a member of the European Union."

"I think it would be a tragedy if we couldn't remain within the European Union, and the biggest threat to the European Union is not whether Scotland votes [for] independence, it's the referendum the British government is going to hold either in 2016 or 2017."

4. Social policy and governing from Westminster

Henderson says issues of social policy have been much less important in the debate.

"It's only really started to surface recently and partly the reason it's started to surface is because the Yes side has changed campaign tactics," she says, stating that the Yes side has been talking more about spending cuts that could come from the U.K. government.

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Recent polls suggest falling support for the No side in the Scottish referendum. (Jeff J Mitchell/Getty)

Key to that debate is the future of the National Health Service.

The present Conservative U.K. government is "trying to dismantle that system," says Murdoch, who believes that if there were an independent Scotland, its main political parties would "all work together collectively to protect the institution."

Muller, while not specifically addressing issues around the NHS, says he finds the idea of government at different levels "wholly unproblematic."

"I am delighted that there are strong and effective Scottish institutions, but I think that there is a strong case for government at [the] U.K. level. I have no problem at all with these decisions being decided by an all-U.K. parliament for which I have a fair and equal vote."

Beyond the issues

While specific issues have been at the forefront of the debate, the discussion seems to reach beyond them to something more fundamental about Scots' involvement in civic life itself.

Muller says his personal motives for opposing Scotland's separation from the U.K. include "an aversion to the nationalist core of the project which makes me — a German national and naturalized U.K. citizen with an English wife — feel alienated and marginalized in what I perceive to be an increasingly narrow and less inclusive cultural and political context."

Murdoch looks at the debate differently and sees one benefit coming out of the run-up to it.

"If nothing else, it's a campaign that's actually got people talking, especially among the younger generation, people in their teens, people in their 20s, talking about politics in a way that we, well I, certainly never did," he said.

"I hope that whatever happens on the 19th [of September], we're all going to work together to maintain this vibrancy that we've got amongst the community and work together to get a better society."