Next year Scots will be asked to make a huge political decision: whether to stay in the UK or to go it alone. As Britain’s Prime Minister I’ve always been clear that this is a decision for people living in Scotland to make. But I do care passionately about the outcome – and I will make the case for the UK with everything I’ve got. For me that case comes down to two things: heart and head.

It’s about heart because our nations share a proud and emotional history. Over three centuries we have built world-renowned institutions like the NHS and BBC, fought for freedom and democracy in two World Wars, and pioneered and traded around the world. Our ancestors explored the world together and our grandfathers went into battle together as do our kith and kin today – and this leaves deep, unbreakable bonds between the peoples of these islands.

But the case for the UK is about head as well as heart – our future as well as our past. I have no time for those who say there is no way Scotland could go it alone. I know first-hand the contribution Scotland and Scots make to Britain’s success – so for me there’s no question about whether Scotland could be an independent nation. The real question is whether it should – whether Scotland is stronger, safer, richer and fairer within our United Kingdom or outside it. And here, I believe, the answer is clear.

Britain is admired around the world as a source of prosperity, power and security. Those glorious Olympics last summer reminded us just what we were capable of when we pull together: Scottish, English, Welsh, Northern Irish, all in the same boat – sometimes literally. If you told many people watching those Olympics around the world that we were going to erect barriers between our people, they’d probably be baffled. Put simply: Britain works. Britain works well. Why break it?

Of course there are difficult challenges to face and tough choices to make. There always are – in government and in our everyday lives.

These wouldn’t disappear if Scotland broke apart from the UK. But those arguing for separation want to force you to make another choice – to choose between Scotland and Britain. I say why should you be forced to make that choice?

Our United Kingdom is four nations united for the common good of all its citizens. With its own Scottish Government and Parliament within the UK, Scots can take important decisions affecting their daily lives: decisions about what their children are taught at school; the way in which hospitals provide care; and how public transport operates across the country.

Scots can take all of these decisions and more to meet the specific needs of Scotland – and they can do so without losing the benefits of being part of the UK and having a full say in its future – economic strength and opportunity, international influence and national security.

Scotland within the UK has a system of government that offers the best of both worlds. Why swap Scottish MPs, Scottish Cabinet Ministers and Scots throughout UK institutions, for one Scottish Ambassador in London?

So what should happen from here until the vote? I know those arguing for independence are already preparing their separation transition plan, as though they’ve got this in the bag, but to me that is wrong. It’s like fast-forwarding to the closing credits before you’ve been allowed to see the movie. The Scottish people still have many months to think about this decision and they are hungry for facts, evidence and expert opinion to help them make up their minds.

As one of Scotland’s two governments, the UK Government has a duty to help inform people with hard facts. So we’ll be providing expert-based analysis to explain Scotland’s place within the UK and how it might change with separation – and our first paper is published tomorrow. We don’t shy away from putting facts and evidence before the Scottish people. We want you to scrutinize, challenge and form your own opinion.

This must not be a leap in the dark, but a decision made in the light of day.

This big question is for Scotland to decide. But the answer matters to all of our United Kingdom. Scotland is better off in Britain. We’re all better off together and poorer apart.

Related information

Read the Scotland Analysis paper: devolution and the implications of Scottish independence.