WITHOUT parodying conventional wisdom too far, many believe that an independent Scotland would be a state of, by, and for the SNP, with Alex Salmond as its perpetual leader, and little or no room for erstwhile Unionists.

The First Minister's speech to the Foreign Press Association last Tuesday changes that conventional wisdom. By announcing his commitment to a written constitution in an independent Scotland, he made a clear distinction between the state – ie, the permanent democratic institutions of Scotland – and the government that might happen to hold office as a result of any given future election. The referendum is nothing less than a choice between two states.

When it comes to the vote, people will be confronted with two boxes. The one marked "No" is a vote for the old, creaking, unwritten UK constitution. This has allowed the Libor scandal, unethical financial services, Leveson, Iraq and the MPs' expenses scandal; where the electoral system is unfit for purpose; the unelected House of Lords cannot be reformed; and where clerics make laws (an arrangement shared only with Iran).

The one marked "Yes" stands for a good constitution, a civic, democratic, Scotland, where the people are sovereign, rights are protected, and government is both representative and responsible. In that new state, governments will come and go; parliamentary majorities will wax and wane; Labour prime ministers of Scotland will spar with SNP leaders of the opposition. The state will belong not to one person, nor one party, but to the whole community of the realm.

Thanks to Salmond's announcement, it has become sensible to ask what an erstwhile Unionist might want from an independent Scotland. And it is likely the former Unionist and the former Nationalist will both want similar things: the protection of fundamental rights; a fair and free electoral process; an independent judiciary; and a political system in which power can peacefully and democratically be transferred from one government to another.

It might seem strange to attach so much importance to an announcement about a constitution. Constitutions, it is often thought, are for dusty legal geeks, and of only peripheral interest to voters concerned with the practical bread-and-butter issues of everyday life.

Through a process of public meetings, research and publications, the Constitutional Commission has been working to dispel this notion, arguing for a clearer understanding of what is at stake here. We have conducted an important educational drive to make citizens aware of constitutional matters, bringing more light into this heated debate. We contend that nothing has greater bearing on the policies which concern everyday life than the distribution of power in society: who rules; how did they get there; what constraints are placed upon them; who are they accountable to; and how can we get rid of them? These are the key questions that a constitution answers.

The constitution is not only the supreme law that protects rights and democratic processes. It expresses a state's commitment to itself, its citizens, and the rest of humanity. It represents what a nation stands for, and what it will not stand for. Most states believe this is so important that they expressly put it in writing, in one document – capable of being amended, but protected against transitory or unilateral changes by the government of the day.

The adoption of a new constitution will have to wait until after independence, but now is the time for Scots to think about the kind of constitution we need. We must discuss the key institutional provisions – parliament, government, head of state, judiciary, civil service and so on. Luckily, on these matters which actually constitute the organs of self-government, we have good models to work from, and there is unlikely to be major disagreement. This meets the first role of a constitution, which is to provide democratic ground rules and fundamental rights. The Constitutional Commission would like this to be clarified in the forthcoming White Paper and put into an interim constitutional framework from the outset. Interestingly, the Green Party makes much the same argument.

Then, after independence, with the interim constitutional framework in place, a participatory convention can be established, as the Scottish Government suggests, to determine the details of a lasting constitution for approval by the sovereign people.

Everyone, even those unconvinced by independence but desirous of better governance, can get involved in this constitutional conversation: we live here, and if there is to be a Scottish state it ought to be a state that belongs to all of us. We are called to be the founding mothers and fathers of a new and possibly great democracy, and every honest voice, hopeful heart and constructive hand should be encouraged to share in this work.

Writing Scotland: the blueprint for our future nation starts here

By John Drummond