He is wrong because of "Women themselves are children"....
That could be described, at best, as a statement of his times based on biased observation and nothing to do with biological developmental (or, ironically, psychological fact).
The brain development of men and women in terms of emotional maturity relies pretty much on the same "training" as it were. It relies on the same development of the wiring in our brain.
Anyone who can, for example, demonstrate even a degree of self regulation, has developed a degree of emotional maturity. Therefore, those of us who demonstrate significant self regulation are, in effect, adults regardless of gender.
I acknowledge, that in Schopenhauer's day, there were really no significantly advance studies in how we mature, so he was forced, in effect to make a guess. He got it wrong because of the above.
As to....
Postmodern Trendoid III wrote on Jul 2
nd, 2015 at 6:33pm:
He's wrong because you hurt me.
I have previously given you more credit for reading, comprehension and degree of critical thinking.... You see that, I was wrong obviously - like I said, we can all get it wrong with our opinions....
The correct quote is "big children".
Given that more women gravitate to child-rearing and nursing, and not to garbage collection or astrophysics, there must be some genetic predisposition underlying this propensity. Despite a concerted social engineering campaign, the pattern hasn't been altered to much degree.