Don't forget 1603 and all that

The Prime Minister, in claiming that devolution is a threat to the future unity of the United Kingdom, is making the same mistakes he made at the end of the 1992 campaign and during the European election in early summer. The Conservatives suffer d ifficulties on devolution for the same reason as they do on Europe: they have an impoverished and historically inaccurate notion of the state.

When they claim that devolution would involve the United Kingdom being "broken up", they mean it would cease to be a unitary sovereign nation state. They appear to believe that is the only legitimate form of state. It is not: it has never been the only form of state, and in Western Europe it has only been the normal form of state during the short period between 1848 and 1957. Many of the world's most successful states have not been unitary states, have not been nation states and have not been controlledby a single sovereign power.

Only one nation state in modern Europe has had a near-continuous existence as such since the Middle Ages, and that is Portugal. It is no more typical of the state pattern of Europe than the grand duchy of Luxembourg. Nations are not God-given: they are mutable. The nations of the French, the Germans, the Italians and the Spaniards are not begotten but made historically; any claim that Belgium or the Netherlands have always been nation states is untenable.

Nor do all states necessarily have a unitary structure held together by a sovereign power which cannot be controlled but by itself. Spain, like Britain, is a union of several kingdoms brought about by dynastic causes. During what used to be called its "golden century" it was a union of states under the authority of a shared king. Each had its own Cortes (parliament), its own laws and its own customs.

General Franco, like John Major, believed this was a prescription for the break-up of Spain, and turned it into a unitary state with a single sovereign power in Madrid. King Juan Carlos believed this was a mistake and reverted to the older pattern of a union of states. I know no Spaniard who believes the union of Spain is less secure as a result.

Nor does every state have a single sovereign power. The 17th-century Dutch Republic, for example, was a union of seven semi-autonomous provinces involving an almost eternal exercise in consultation. What should, according to modern Conservative principles, have led to the collapse of the state led instead to what the English ambassador called "their prosperity beyond man's discourse". The sovereignty of the people in the United States is no more than theoretical. Their constitution set up a system of power-sharing.

In June, Mr Major made it clear that he does not understand that Britain is not a nation state. Britain was created in 1603 when James VI of Scotland inherited the throne of England and created the Union of the Crowns. This arrangement, which lasted 104 years, was a union of sovereign nation states under a common authority - a pattern more like the modern European Union than anything else with which we are familiar. James, in London, governed Scotland by what was, in effect, a system of devolution through a Scottish privy council and Scottish parliament in Edinburgh. The inevitable conflicts were mediated through the King's Bedchamber (the 17th-century equivalent of the Downing Street Policy Unit) in London. The system worked because the Scots attending the King in London and the Scots running the Privy Council in Edinburgh were personal friends and able to negotiate differences.

The system broke down in 1707 because England and Scotland did not have a common law of succession - a problem which will not be repeated under devolution. The Act of Union of 1707, which created a single state of Britain, was in the form of an international treaty. A Treaty of Union between two nations, in whatever constitutional form it may be expressed, can and should last no longer than both nations wish it to continue. If Mr Major does not accept that we are two nations, he might like to watch nexttime England plays at Hampden Park or Murrayfield and deny that he is watching an international.

Though Britain has been in the form of a single state, it has never been a completely unitary state. Those who discussed union in the 17th century used to argue, in much the same terms as Mr Major, that Britain could not be a single state until Scottish law was abolished and the state had a single system of law. They were wrong. The Act of Union also tried to limit the sovereignty of the Westminster parliament by forbidding it to legislate for the Scottish church. So even Britain fails to fit the stereotype of the unitary sovereign nation state. If we have got on so long without it, it cannot be indispensable.

Until we abandon the idea that the unitary sovereign nation state is the only form of political power and that anything else would "break up" the United Kingdom, we cannot even discuss some urgent questions. If we did make the change, we would be joiningthe majority. Whether that is wise or not, it must be an option.

Conrad Russell is professor of British history at King's College, London, and visiting Sir Henry Savile professor at Merton College, Oxford.