Looking back on myself when I was 18, I'd have to disagree. At 18, I knew very, very little. Almost nothing about how the world worked. It took a lot of education - and self education - to understand the world more fully. My 18 year old self is an idiot compared to my 25 year old self and completely retarded compared to my 40 year old self. Also, people's brains stop developing around 25 years old, so there's still more biological maturing that needs to happen. Last, teenagers want to uproot the whole world because everything seems unfair. One big difference me of 18 and me of 25 is the ability to come to terms with the unfairness of life and differentiate unfairness due to misfortune and unfairness due to unjust, conscious action. That was difficult for me then.