The case for keeping Scotland in the UK is "unquestionable", the Prime Minister has insisted.
Keeping the UK together is one of the "huge battles" faced by the Conservatives in the coming years, David Cameron said, as he pledged he will fight "every step of the way" to keep the country together.
With people in Scotland to vote in the independence referendum next year, Mr Cameron used his speech at the Scottish Conservatives' party conference in Stirling to make the case for the Union.
He defended the coalition Government's controversial welfare reforms, telling Tory activists they should be "proud that we're the party making the bold case on welfare".
With the UK spending review due later this month, the Prime Minister said there is "no turning back" with austerity, adding that the UK is not only stronger together but is also richer together, he said.
Addressing the independence debate, Mr Cameron told delegates: "Let's show that our case stacks up on paper. But let's also make sure it resonates with people too. Win in the head, and win in the heart."
The case for the Union is "not just about the cold, hard facts". The Prime Minister added: "It goes much, much deeper than that. This is about the future of our island. The next chapter in our story."
Mr Cameron said Scotland should remain part of a "dynamic, enterprising, prosperous, compassionate Britain" and that the UK should be a "country where we are cutting our deficit, not arguing about how to divide it up" and where "we are fixing welfare, not doubling the problem by splitting up".
He added: "Together we're unbeatable. United we're unstoppable. The case is unquestionable. Head, heart, body and soul, we will fight for our United Kingdom every step of the way."