"In Scotland, the people are sovereign". This is the foundation of the interim constitution that has been published in a draft bill by the Scottish government. In the event of a yes vote, this would provide the basis for the Scottish state during the first years of independence, pending the adoption of a permanent constitution some time after 2016.

The pro-independence parties – the Scottish National and Scottish Green parties – have long been committed to a written constitution. They envisage a country based, in common with the vast majority of the world's democracies, on a constitution that organises its institutions and protects fundamental rights. Their position is partly pragmatic. While an old established state, which retains the essence of pre-democratic institutions, may "muddle through" for centuries without clear constitutional protections, a newly independent state would need a written constitution to define itself, to reassure its citizens, to constrain its politicians, and to be taken seriously around the world.

A new constitution is also a way of giving effect to democratic principles and values. The interim constitution puts the people first, as well as proclaiming the principle of popular sovereignty and asserting that "the form of government in Scotland is a parliamentary democracy". It embodies the European convention on human rights, asserts the accountability of the government to the people, and calls on public officials to act with "integrity, honesty, objectivity and impartiality".

At a time when the UK government is celebrating Magna Carta and trying to enforce "British values" in schools; when the British establishment seems incapable of reforming either the electoral system or the House of Lords; and when even the moderate gains of the Human Rights Act are under threat – the Scottish government presents a more mature, principled and democratic constitutional settlement, with the sovereignty of the people at its core.

The draft interim constitution builds on an impressive record of Scottish institutional progress with cross-party appeal. Scotland already uses proportional representation. The powers of the crown in Scotland, with regard to the appointment of the first minister and the dissolution of parliament, are already curtailed by the Scotland Act. The "claim of right" – an assertion of popular sovereignty – was endorsed by the Scottish parliament with the aid of Labour and Liberal Democrat, as well as SNP and Green, votes. With these principles so widely endorsed across the political spectrum, it is hard to portray the draft constitution as stemming from the SNP alone.

As a document for consultation, the draft constitution leaves room for improvement. Even as an interim text, it is somewhat skeletal. Key institutional provisions, such as the electoral system and parliamentary terms of office, are not mentioned. It is envisaged that these provisions would be regulated by a revised Scotland Act. Transposing the relevant provisions of the act into the constitution would be a neater solution, and would reinforce the constitution's status and authority.

A more serious technical concern is the absence of entrenchment. Under present plans, the interim constitution and the Scotland Act would be amendable by an ordinary majority in parliament. This weakens the whole edifice, as constitutional guarantees would be subject to the political decisions of the parliamentary majority.

The interim constitution offers an independent Scotland a different future from that available in the UK: one where the people are acknowledged as the source of public power. A provision preventing laws changing the constitution from being enacted – unless endorsed either by a super-majority of parliament or by a referendum – would do much to help this interim constitution live up to these exciting promises.