[oh_sigh]

> Why shouldn't we impose the same restrictions on say, a senile 95 year old with the mental age of 5 year old?

In that case, you aren't discriminating based on age. Unless you think for some reason that a 95 year old with the mental capacity of a 5 year old doesn't deserve a vote, but a 40 year old with the mental capacity of a 5 year old does deserve a vote.

[MaxfordAndSons]

Good point, in the case of voting it's a matter of mental age/capacity, not physical age. But I think there are analogous situations where it makes sense to age discriminate on both end for primarily physical reasons - contact sports, voluntary exposure to high g-forces, etc.