Emily Thornberry is a forceful substitute for Jeremy Corbyn during Prime Minister’s Questions. But she was given as good as she got during her last outing. At the age of 16, she told the Commons last month, “we are free from parental control, we can leave home, we can start a family, we can get married, we can start work, we can pay taxes and we can join the forces.” So why – she asked David Lidington, who was standing in for Theresa May – can’t we vote?

This gave the well-briefed Cabinet Office Minister the opportunity to point out that it was “the last Labour Government who raised the legal age for buying cigarettes to 18, raised the age for selling knives to 18, raised the age for buying fireworks to 18 and raised the age for using a sunbed to 18”. Cue sound of punctured Thornberry.

Put party politics aside for a moment – votes at 16 would almost certainly favour Labour over the Conservatives – and weigh these curiosities. They are the right way of beginning to think about the matter, which the Commons will debate again sooner rather than later. A Bill tabled by a Labour MP failed last autumn. Another tabled by another is looking for its turn. On this site earlier this week, Nicky Morgan declared herself in favour. Peter Bottomley thinks likewise. So does Justine Greening. George Osborne has tweeted, with the engaging cynicism that so distinguishes him, that the Commons numbers give the Conservatives a choice. Back the winning side, and win credit for supporting another piece of social reform. Or else line up with a losing cause, and go down in flames – and further down in votes, too, among younger people.

In the short-term, he may be wrong. One private members’ bill has been talked out; the next may well be, too. But in the longer-term, the former Chancellor may have a point. The history of legislation is a journey from the heretical to the conventional: universal suffrage, votes for women, race relations laws, same-sex marriage, equalities legislation that protects disabled people.

It’s true that what may seem to be the march of progress can lead instead up a blind alley. Take eugenics. It was once backed by a big slice of the great and the good, including Winston Churchill; the then Archbishop of Canterbury; H.G.Wells, and the Webbs. (Who knows what convention of the age will seem an outrage in 50 years time?) But votes at 16 cannot reasonably be seen in the same light. And the flow of private members’ bills looks set to continue. We’re unaware of any sustained shift in polling that would back them up – even among the youngest tranche of voters, or people aged 16 or younger. None the less, Tories in general, and the Government in particular, should handle votes at 16 with care, given the division of the electorate by age last summer. The next generation is unlikely to be impressed by grumpy old sourpusses telling them that they’re too young to hold views that matter.

Instead, think again about those misapprehensions and incongruities. Thornberry said that one can pay taxes at 16. Yes, but one can at any age. She claimed that “we are free from parental control…we are free to get married”. Not so, outside Scotland. She said that we can join the armed forces – but, again, parental permission is required.

During the 1950s, only three per cent of young people went to University. Now, almost half do. So if entry to the world of work is thought to be the arbiter of the right to vote, the case for votes at 16 has actually gone backwards. But if one’s looking for arguments to the contrary, there is driving. One can do so at 17 – 16 in some cases – and yet not vote. And 16 year olds in one part of the country have voted. They did so during the Scottish referendum: Morgan’s argument for votes at 16 was precisely that this cat has been let out of the bag. But what would 16 or 17 year olds think were they allowed to vote, but not smoke? Push a piece of paper into a ballot box, but not lay themselves down on a sunbed? Register for a postal vote, but not buy a Roman candle? Some might feel just a bit, well, patronised, to use a word that sometimes comes up in this context.

This site feels a commission, a working group, an inquiry coming on – to look these inconsistencies, accidents of history and quirks, and see if some tidying-up and straightening-up is required. The long grass, we hear readers say. Yes: but the longest, the lushest, the deepest grass. The horses of prevarication are wiser than the tigers of denial. Better the long grass than No You Can’t.

And at the end of the process, one might be a bit nearer votes at 16. Or one might not. Experience abroad is not helpful to the cause. There is no firm evidence that lowering the voting age increases democratic participation. None of our EU neighbours, bar Austria, has votes at 16. We appreciate that Britain is leaving the Union, but there can be too much of a good thing.