I love Waitangi Day, love it for the history that hangs in the air and the tension that radiates from the Treaty grounds no matter what happens. I don't want the fireworks and frivolity of Australia Day, I prefer the truth.

I love it that we are haunted by a founding pact we can barely explain. I spent months last year studying other states established by British colonialism and none were quite like us. Treaties were made with other tribes of other places but not in the spirit of ours.

This country was not to be colonised without the consent of the natives. The chiefs who signed the Treaty probably did so for the sake of peace, good government and reliable law, all of which had become scarce commodities in Maori society since the arrival of firearms.

The convulsions the "musket wars" caused have been an unfashionable subject of historical research, but nothing else explains why powerful people would hand so much authority to the distant ruler of a tiny white minority.

Quite what sort of authority they had in mind is still a matter of academic debate. Possibly the chiefs imagined they were simply signing up with the British Empire, the most powerful entity in the world at the time, and could retain the kind of sovereignty that people of distinct ethnicity generally enjoyed in European empires of the 19th century.

Some Maori had travelled. They had seen a world that was not yet ruled entirely by nation states. Most of Europe was still governed as it had been for centuries, by imperial dynasties such as the Habsburg and Ottoman.

Those empires, when you study them today, were surprisingly liberal. For a long time they had been able to satisfy many different ethnic and religious constituents by according them a high degree of self-government.

The distinct ethnic strains spoke and wrote of themselves as "nations" without challenging the empire's authority overall. In fact they took pride in both their cultural nationality and their participation in a larger cosmopolitan state.

Habsburg Vienna, for example, was one of the cultural capitals of the age and Czechs, Jews, Hungarians and others were as prominent as Austrian Germans in its literary and political life.

Nationalism as we know it developed later in the 19th century, when liberal thinking decided that no nation was free unless it became an independent state.

During the 20th century that idea became so entrenched that the terms nation and state are now commonly used synonymously and it is inconceivable to most people that their state could comprise more than one nation.

But in 1840 all of that was still to come. When Maori looked around the globe at that time they saw not only the liberal empires of the European continent but free colonies on the Australian mainland where the Queen's writ was orderly without being oppressive.

That, I suspect, is what they signed up for. What they got was that, and much more. Namely, immigrants. Many more than they can have imagined.

It is easy to say in hindsight that they should have seen what would happen. But power can blind people to potential danger and the Maori who signed the Treaty still held power. They probably felt they could control any consequences.

By the time they realised what was happening the die was cast. A few rebelled. Most tried to make the best of it. Perhaps they decided that law and government were still preferable to what prevailed before.

But Britain soon handed government to the settlers and the law turned out to be an instrument for the division and transfer of land.

That's the truth. But the Treaty survives. It probably has a higher place in our consciousness now than it has ever had, and that is true of both sides in the debate over its meaning.

Don Brash will be at Waitangi this week because he thinks the Treaty made us one nation. Many Maori are there because it enshrines their sense of a distinct national sovereignty.

Early in his address at Orewa this week Brash re-affirmed his belief that "race" has no place in the decisions he would make for New Zealand.

Near the end of the speech he intimated his party would propose greater restrictions on immigration to preserve "our common values".

I got a chance to tell Brash directly this week that it doesn't really matter what he thinks or what I think. If Maori think we are not one nation, we are not.

If Maori are a nation they will organise themselves politically to give independent expression to themselves in the New Zealand state. They have now partially separated their parliamentary representation from the Labour Party and have four independent seats in the House.

The annual forum at Waitangi's Te Tii marae this weekend will hear a hint of the immense possibilities those seats present. The only thing the rest of us have to argue about is what we should do in response.

We could do what Brash suggests. We could abolish the Maori seats in Parliament, cancel all "race-based" health, education and welfare programmes, give tribes no more recognition than anybody else when developments are proposed in their traditional territory.

We could do all that, and worse, and Maori would probably endure it.

But Brash is not a tyrant and we are not a tyrannical majority. Sooner or later Maori will carve out a powerful place for themselves in New Zealand's politics and make this state express their national will and character as well as mine.

It may start to happen this year if the Maori Party sets about building a broad constituency.

The most the majority of us can do is thank goodness for the Treaty. It was a pact between distinct and powerful people to form a proud state for both, and we hear its echo wherever we are on Waitangi Day.

It was a great idea and it is going to be great when our descendants get there.