Dear Nathan,

What you say is well and good - therefore the solution is to remove this arbitrary imposition called "18" altogether rather than shift it to "21".

You are very lucky that at the age of 18 you were allowed to stay at home, continue your education or otherwise do what you like - at that same age I was forced into the army, against my will. In fact I was already studying in university at the time, but was not allowed to continue.

Fortunately in Australia (for now), nothing forces you to move when you are "18" - that some idiot, perhaps a teacher, happened to say so and scare you with that number, whoever did so has no power over you and you can simply tell them to piss-off!

Nobody has a right to tell you what you may or may not do because you are deemed to be more developed or less developed: your life should be your own from the moment you are born, to do with it as you please (provided you do not hurt others). Also, while you raise concerns for those who are slow to develop, or of lower capacity, you should also consider the pledge of those who are of higher capacity and faster to develop: certainly they should not be punished or disadvantaged for not reaching some arbitrary number of years.

It is well known that a person's ability to assess risk and decision making is not fully formed until 25, but improves dramatically from 16 to 18. This is reflected in insurance loadings that heavily penalise drivers under 25, and even higher those under 20. Raising the age restricts people from making their own life decisions, and lowering the age exposes everyone to rash decisions.

However, there needs to be a line drawn somewhere, and at age 18, people leave schools and work for themselves. They can make their own life decisions and need to be responsible for them.

If you push kids instead of coddling them and barring any mental impairment they're usually capable adults by 18 plus the newer tradition of sharing accommodation with other young people provides many of the same benefits for social development as family life. Living in share houses in my twenties I passed some of the happiest years of my life, under the best of circumstances sharing household responsibilities with four or five other people you do become a sort of family whose members guide and protect each other.

I seem to recall the adult age being 21 while Lib governments were conscripting 18-year-olds to fight America's colonial war against Vietnam.