The air in Scotland hangs heavy with history. Edinburgh's cityscape is studded with monuments to memories.
Walter Scott, Robert Louis Stevenson and John Knox all compete for our attention. In Dundee, Captain Scott's Discovery lies at anchor. In Aberdeen, King's and Marischal Colleges remind us of a time when the Granite City had as many universities for its citizens as England had for all of hers.
And while the hauntingly empty acres of the Highlands stand in mute memorial to the injustices visited on the victims of the clearances, Glasgow's magnificent architecture and art galleries remind us of the mercantile greatness of the Empire's second city.
For politicians north and south of the border, however, there is a danger of living in the past when thinking of Scotland. That is partly because its history is populated so thickly with great men and women who we might want to conscript for our contemporary battles.
Those of us on the centre-right will pray in aid of Adam Smith and David Hume, economic liberals and philosophical conservatives whose enlightenment thought laid the basis for later political action.
On the left, the examples of James Maxton and Keir Hardie can still inspire class strugglers to one more heave.
This has been a pioneering country all its life. As a home of learning in medieval times. A nursery of literacy and learning at the time of the Reformation. A champion of liberty during the Enlightenment. The turbine hall of the Industrial Revolution. A recruiting ground for freedom's fighters in two world wars. The birthplace of John Reith, who gave us public service broadcasting and as a powerful contributor to the last twenty-five years of economic growth. Scotland has much of which to be proud.
And one of the reasons we are tempted to look backwards is precisely because Scotland as a nation - and as part of the United Kingdom for over 300 years - has achieved so much.
But proud as that past and present are, I am convinced that for both Scotland, and the United Kingdom, our best days lie ahead of us.
And that even though it may be a great historical construct, the United Kingdom is actually even more of an inspiring model for the future.
Think of the key challenges of our times.
There's the risks and opportunities of globalisation - with populations moving, cultures clashing and new routes to prosperity.
And there's the impact of increasing economic competition from the new, economic power houses of the world.
The United Kingdom has the answers to both.
In an increasingly uncertain world, where risks proliferate and atomisation threatens our ability to look out for one another, nothing encapsulates the principle of pooling risk, sharing resources and standing together with your neighbour better than the United Kingdom.
Whether it's ensuring the same disability benefits for those in need from Motherwell to Maidstone or ensuring that the resources of sixty million taxpayers stand behind our banks.
Whether in Edinburgh or London, the United Kingdom is a warm and stable home that billions elsewhere envy.
And in an increasingly competitive world, where the future belongs to those who can collaborate, innovate and co-operate together best. The support a nation of sixty million can give, for example, to knowledge exchange between bio-engineers in Edinburgh and Oxford and venture capital for the best start-ups could be the envy of others.
So - I come here today with one simple message: I hope and wish that Scotland will vote to remain part of the UK.
That's not because I want to dragoon Scotland into an arrangement which is in my interests. Or, frankly, my party's interests.
I know the Conservative Party isn't currently Scotland's most influential political movement and so more than a little humility is called for when any contemporary Tory speaks in Scotland.
In fact some say it might be wiser not to speak at all.
As well as avoiding any criticism from the press - or politicians from other parties for "interfering" - it might be thought wise of me to just let Scotland, in every sense, go its own way.
And some people, not all of them Tories, have suggested that an independent Scotland might make it easier for my party to get a majority in Westminster. But that doesn't interest me.
I'm not here to make a case on behalf of my party, its interests or its approach to office.
I'm here to stand up and speak out for what I believe in. I believe in the United Kingdom. I'm a Unionist head, heart and soul. I believe that England, Scotland, Wales and Northern Ireland are stronger together than they would ever be apart.
It is time to speak out, whatever the consequences, because something very special is in danger - the ties which bind us in the country we call home.
The danger comes from the determination of the Scottish National Party to remove Scotland from our shared home.
Now it is absolutely right that since the SNP won the Scottish elections, they should be able to determine the business of the Scottish Parliament and the agenda of the Scottish Government.
They want to put the question of independence to the Scottish people and their ultimate ambition is clear: they want Scotland to leave the United Kingdom.
And it is right too that the choice over independence should be for the Scottish people to make.
But that choice should not be made - with its consequences for all of us - without explaining why I believe in the United Kingdom, and why it matters to so many of us.
Let's be clear, though, I'm not going to stand here and suggest Scotland couldn't make a go of being on its own, if that's what people decide. There are plenty of small, independent nation states of a similar size or even smaller.
Scotland could make its way in the world alongside countries like those.
Of course, every country in the world is facing new challenges and an independent Scotland would itself need to confront some big issues. There are those who argue about the volatility of dependence on oil, or the problems of debt and a big banking system.
And there is for some smaller nations the risk that independence can actually lead to greater dependence.
Certainly today Scotland has a currency which takes into account the needs of the Scottish economy as well as the rest of the United Kingdom when setting interest rates.
And it can borrow on rates that are amongst the lowest in Europe.
An independent Scotland would have to negotiate in future for things it now gets as of right.
But these challenges and the need to overcome them, they are not my point today.
My argument is simple. Of course Scotland could govern itself. So could England. But we do it so much better together.
I can - and will - enumerate a number of practical reasons for our United Kingdom.
But the reason I make the case is - partly - emotional. Because this is a question of the heart as well as the head.
The United Kingdom isn't just some sort of deal, to be reduced to the lowest common denominator.
It's a precious thing. It's about our history, our values, our shared identity and our joint place in the world.
I am not just proud of the Union because it is useful. I'm proud because it shapes and strengthens us all.
Just think of what we've achieved together. Scotland has contributed to the greatest political, cultural and social success story of the last three hundred years, the creation and flourishing of a United Kingdom built on freedom and inclusivity.
Individual nations can of course adhere around ancient myths, blood-soaked memories and opposition to others. But we have built a United Kingdom that also coheres around the values embodied in standing up for freedom and democracy around the globe. In free healthcare for all. Generous welfare for the poorest and championing the most vulnerable on the world stage.
A United Kingdom which is not monoglot, monochrome and minimalist but multi-national, multi-cultural and modern in every way. Our United Kingdom.
Founded on the strengths of our constitutional monarchy, parliamentary democracy and the rule of law. It's also the birthplace of the NHS, the BBC and Christian Aid.
We have shared achievements that more than match those of any other country in the world.
From Waterloo to the Second World War our servicemen and women have fought and won together. The liberation of Europe was a battle fought to the skirl of the pipes as Lord Lovat's Highlanders were among the first ashore on D-Day in the battle to defeat Hitler.
Your heroes are our heroes.
Men like Robert Dunsire who twice in one day crawled out of the trenches facing a hail of bullets to rescue injured men at the Battle of Loos. And Lance Corporal Liam Tasker - the dog handler who helped to save so many lives in Afghanistan before tragically being shot.
The Union has never been about shackling different nations: it's a free partnership, a joint effort, often driven by Scottish ideas and Scottish leadership.
From the industrial and commercial leadership of James Watt and Robert Owen centuries ago to Sir Bill Gammell and Ian Wood today.
And in Westminster the cause of progress has depended on the voices of politicians from Scotland - whether its been the liberalism of Henry Campbell-Bannerman and Joe Grimond. The progressive conservatism of Iain Macleod and George Younger, or the generous and humane radicalism of Donald Dewar and John Smith.
Together we have turned a group of off-shore European islands into one of the most successful countries in the world. But it's not just about what we have achieved together. It's about who we are together.
The ties of blood grow thicker. Far from growing apart we're actually growing together.
There are now more Scots living in England and English people living in Scotland than ever before. And almost half of Scots now have English relatives.
I am a classic case. My father's father was a Cameron. My mother's mother was a Llewellyn. I was born and have always lived in England.
I am proud to be English - but like so many others, I am proud to be British too.
Proud of the United Kingdom and Scotland's place within it.
Then there are the practical reasons for the Union to stay together. The Union helps to make Scotland stronger, safer, richer and fairer.
We're stronger, because through our shared Union we count for more together in the world than we would apart.
We have a permanent place on the UN Security Council real clout in NATO and Europe and unique influence with key allies all over the world.
Scottish pilots helped us to free Libya from tyranny and prevented a failed pariah state festering on Europe's Southern border potentially threatening our security and creating a more dangerous and uncertain world for Britain and for all our allies as well as for the people of Libya.
We're safer, not just because of the expertise and bravery our armed forces to which Scotland makes an immense contribution but also because of our policing expertise and security services respected the world over.
When a bomb went off at Glasgow Airport the full resources of the UK state went into running down every lead. Our tentacles reach from the border areas of Afghanistan and Pakistan to the CIA computers at Langley.
We're richer, because Scotland's 5 million people are part of an economy of 60 million with no boundaries, borders or customs but a common system, rules and currency which has helped to make us the 7th largest economy in the world.
And far from growing apart our economies are growing together. A fifth of all Scottish workers are employed by firms registered in Scotland but owned by companies based elsewhere in rest of the UK. And Scotland sells twice as much to the rest of the UK as to the rest of the world put together.
And we're fairer. Not just because we all benefit from being part of a properly-funded welfare system, with the resources to fund our pensions and health-care needs, but because there is real solidarity in our United Kingdom.
When any part of the United Kingdom suffers a shock or a set back, the rest of the country stands behind it. Whether it is floods in the West Country, severe weather in the north or the economic dislocation that has hit different parts of our economy at different times and in different ways we are there for each other.
And together we have the power to do much in the world to promote fairness. One issue that is very close to my heart is aid. And this is an issue where Scottish people have a huge influence.
Together as a UK we have the 2nd biggest aid budget in the world. Through the UK, Scotland has global reach. And with that we are saving thousands of lives and helping people in some of the poorest parts of the world to forge a new future.
From the famine in the Horn of Africa to the support for people in North Africa and the Middle East as they seek new freedoms that we and others take for granted.
So I believe there are emotional and practical reasons why the Scotland is better off in the Union - and why we are all better off together than apart. But I don't think that is enough.
I also understand why people in Scotland want to express their identity as Scots strongly and to have greater control over their lives. I believe in real devolution and want to make devolution work better.
I want a Scotland where more people own their own homes. Where more people keep more of their money. With secure jobs and a secure future for their children.
A Scotland where businesses can innovate and create the wealth and opportunities so vital to local communities breaking down the barriers to entrepreneurship that have for too long held Scotland back.
I believe in devolution not because I see it as a mechanism for obtaining power - hardly the case for my party in Scotland - but because I believe in giving people choice and a real say of their own affairs.
I passionately believe that local is best. And the decentralisation of power is one of the core aims of the Coalition government I lead.
One of my first acts as Prime Minister of the United Kingdom was to come here to Scotland to meet Alex Salmond and to show that I want the governments in Westminster and Holyrood - whoever they are and whichever party they are from - to work together to get the best for Scotland.
To listen to Scotland - to act on Scotland's voice and govern in Scotland's interests.
On that first visit I said the only political input into senior Scottish civil service appointments should come from the First Minister and I delegated my previous responsibility to the Cabinet Secretary.
A small symbolic gesture of the kind of change I want to bring about. Since then Ministers in Holyrood and Westminster have been meeting regularly. And soon a much bigger change will become law.
The Scotland Bill hasn't got the attention yet that it deserves. But it's an incredible opportunity for Scots.
Not London telling Edinburgh which powers it can have - but opening up Scotland's choice to expand the ones it needs.
By implementing the recommendations of the Calman Commission - devolving new powers to the Scottish Parliament including for the first time the ability to raise tax revenue and borrow for capital and current expenditure the Scottish government is getting real choice over how and when to invest in long-term projects that will benefit future generations.
And let me say something else about devolution. That doesn't have to be the end of the road.
When the referendum on independence is over, I am open to looking at how the devolved settlement can be improved further. And yes, that means considering what further powers could be devolved.
But that must be a question for after the referendum, when Scotland has made its choice about the fundamental question of independence.
When Scotland has settled this question once and for all - and ended the uncertainty that could damage and hold back Scotland's prospects and potential.
So I believe the strengths that have served us through the centuries are precisely the ones we most need today.
Our United Kingdom is a modern Union: one that evolves, that protects us and that allows our different nations to grow stronger because we share the same secure foundations - institutions that celebrate diversity and turn it into a strength.
Scotland's greatest poet said we should "see ourselves as others see us" - and that's worth doing.
Because our Union isn't some antique imposition. It's living, free and adaptable.
It's admired around the world as a source of prosperity, power and security.
Just think for a moment: could you explain to someone in America, or France, or Australia what was so intolerable about Great Britain that we decided to build artificial barriers between our nations?
I don't believe that the people of Scotland any more than the people of any other part of the United Kingdom want to turn inward and away from each other at this time.
I believe - indeed it's my reason for being in politics - that it's when you pull together, when you set aside difference, when you roll up your sleeves in a common endeavour you can achieve things which are truly worthwhile, even noble, which you could never accomplish on your own.
For me the principle that we work best when we work together without coercion or conscription, bullying or bossiness, in a spirit of shared service sums up what's best about our countries.
That's what the United Kingdom stands for - common endeavour.
Being part of something bigger - a greater Britain in which the virtues of sharing, standing together and making a difference for our fellow citizens guide our every action.
If anything's worth fighting for that surely is; which is why I'm ready for the fight for our country's life.