So, in general, it seems like we're okay with discriminating people based on essential mutable characteristics and non-essential characteristics, but not based on essential immutable characteristics.

Illnesses are non-essential characteristics. A human doesn't necessarily have an illness. We're okay with discriminating towards people based on this. You can't become a pilot if you have severe problems with your vision and you can't operate heavy machinery if you get regular seizures.

Age is essential, a human must have an age, but it's mutable. A human must also have a height and weight, but they're also mutable. We're generally okay with discriminating based on all of these. You can't go on certain rides if you're too tall or too short, you can't vote if you're too young, you can't ride horses if you're too heavy and you can't give blood if you're too light.

Race, sex and sexuality are essential and immutable. In the west people seem to be converging on it not being okay to discriminate based on essential immutable characteristics. I agree with this and I see race, sex, sexuality as far more intimately tied to the essence of a human being than their age, height, weight or list of illnesses.

If you disagree with these distinctions and groupings, that's fine. But then I don't think there's much of a point in us continuing as it'll simply take too long, heh.

So, having read all of the above, my first objection to myself is "So I think we should be okay with taking a person's right to vote based on their height? It falls in the same category as age.". To that objection I'd say no, we should not. Note that in all the above examples of discrimination the basis for the discrimination is that the discriminated group can't do the activity safely/competently. We're usually not okay with baseless discrimination. You can't disallow disabled people from buying your cake, you can't disallow short people from eating at your restaurant and you can't disallow young people from operating a camera. These would all be baseless and the characteristics being discriminated don't relate to the actions in any meaningful way.

In this same sense, young people can't vote safely/competently and voting is important enough for us to desire safe/competent voting. A young persons brain simply is not developed enough to be able to reason in some ways an adult can. A young person is also far too attached to their parents. The parents will have such a huge amount of influence that giving children the right to vote is the same as giving their parent another vote.

Now, this leads to another conclusion which I'm not entirely comfortable with. If we're okay with not giving a person the right to vote based on age-caused lack of reasoning ability, shouldn't we also be taking away the ability to vote from adults who are deemed to have the reasoning ability of someone below the age of majority? I'm not sure to be honest. I suppose we're just legislating for the average though and the average person above the age of majority has a greater reasoning ability than the average person below the age of majority. So even people well below the average, below even the young people average, are treated as though they're average.

This says nothing about what the age of majority should be, mind you. 18? 12? 45? Who knows. But I find it reasonable that a age limit should exist and that it has enough basis to still call it a democracy.

Thank you for attending my TED talk :)