I define full adulthood as being the age of what I call Full Legal Responsibility. This is the age at which if you break any law, you are held fully accountable for your actions and do not receive a lesser penalty for being a minor. This is where the legal age for drinking or engaging in other such vices should be set, and no higher.
In a nutshell, with full legal rights should come full legal responsibilities. On the other hand, with full legal responsibilities should come full legal rights.
For example, if you are considered a fully responsible adult in the eyes of the law at age 18, by which I mean if for example, at age 18, you are charged with say, drug trafficking, would face the full criminal penalty if found guilty, then it is reasonable that you should be able to choose to drink alcohol or engage in any other legal vice you care to think of.
In this case, we should also stop referring to 18-20-year-olds as "youth". A youth is someone not yet a legal adult, that is, under 18 years of age, and using this term to refer to 18-20-year-olds only reinforces the fallacious view that they are not adults. This is the mistake American "youth rights" campaigners keep making when arguing for a lower drinking age. Having the drinking age at 18 is NOT about youth rights, it's about the rights of adults aged 18 to 20.
It should be emphasised that a 'minor' is legally defined as someone under the age of majority, that is, under 18 years of age in most countries and US states. Using the term to refer to people under the age of 21 is not legally correct.
I advocate that 18-20-year-olds from across America gather on Capitol Hill with adult size dummies to protest against the drinking age and other such laws that treat them as children.
On the other hand, we could just define legal adulthood at 21 instead of at 18. But then 18-20-year-olds, if they break the law, must be treated as minors in the justice system, not face the full penalties for most crimes, and be sent to separate juvenile prisons. An age restriction of 21 to purchase and consume either alcohol or legal cannabis may be reasonable in this case.
18 may still be defined as the age of 'majority', that is, the age at which you gain independence from your parents and are no longer considered a 'minor'. It may also be set as the age at which you can vote and do a whole range of other things. But it is not the same as Full Legal Responsibility, which could be set at 21 years of age.
What do you think? Do you think you should be considered a full legal adult at 18 or at 21? I would like to hear your point of view and engage in a constructive debate. So feel free to comment.