We are celebrating, in Britain today, the centenary of women winning the right to vote. In 1918, the vote was extended to all men over 21, and to women of the propertied class and over 30 years of age. It was to be ten more years before all women over 21 got the vote.

We are used to thinking that with all adult men and women having the vote, and the voting age having been lowered to usually 18, we have achieved universal suffrage. But that is not right. A whole class of citizens are still denied the power of the vote: children.

That matters. The interests of children are light-weight in the competition over public policy. The Family Allowance that was introduced in the great welfare reforms at the end of World War II, has subsequently shrivelled in real value, the result being high rates of poverty among children. It has not had enough political support. In the great austerity drive after 2008, pensions have been singularly protected from any erosion in value. Pensioners have the vote and use it.

It is mostly though obvious that children cannot have the vote, but that is sloppy thinking. It was once thought obvious that women could not vote. The battle against “the obvious” is the first bastion. In The Subjection of Women (1869) John Stuart Mill said it thus: “.. the burthen is hard on those who attack an almost universal opinion ..”

The logic is that children should not have the vote because they cannot vote, but that is to confuse two separate questions, the should-question and the could-question. If we for a moment set practicalities aside in our minds, and ask only the should-question, we would surely conclude, theoretically, that children should have the vote. The principle of universal suffrage is that all citizens have an equal interest in government matters and that therefore all citizens should have an equal say. In the abstract, that must include children no less than other categories of citizens.

The question, then, is really if they could have the vote. If a practical way could be found, there is no issue of principle standing in the way.

In recent years, great advances have been made in the recognition of children’s rights. In many ways children are now, in law, citizens rather than subjects. For example, children have property rights. Children cannot manage property, but that is not taken to mean that they cannot have property. The practical solution is that someone is appointed to be the custodian of the property on behalf of the child, until the child is old enough to take care of it himself or herself. The custodian has a duty to manage the property in the best interest of the young owner.

The similar logic in respect to the vote would be that all children have the right to vote but that this right is managed on behalf of the child by a custodian until the child comes of age, now sometimes referred to as demeny voting.. That’s a practical solution that solves the could-question. Since there is no independent should-question standing in the way, the matter should be resolved.

The solution I have advocated  is that the children’s vote is managed on their behalf by the mother (or the father if the mother is absent) so that the mother is the custodian of a second vote in addition to her own irrespective of the number of children. There are other ways it could be done, but this has been my preferred arrangement. There is every reason to trust that mothers would manage the second vote on behalf of their children and not as a second vote for themselves, just as we trust custodians to manage property.

There is a small lobby in democratic countries in favour of the children’s vote. Not a powerful lobby – we have not yet won the battle against “the obvious” – but a persistent lobby. I first lent my voice to this following in an article in the then International Herald Tribune on 14 December 1996, under the heading “In a Democracy, Children Should get the Vote.” The progress that is being made is for a lowering of the voting age to 16, which has been introduced in some democracies and is coming elsewhere. But since there is a way that concurs with current legal thinking to include all children in the power of the vote, there should be no reason not to go the whole way.