Youth ages, immaturity is outgrown, ignorance can be educated, drunkenness sobered, but stupid lasts forever.
Aristophanes
For many, immaturity is an ideal, not a defect.
Mason Cooley
Immaturity is the incapacity to use one's intelligence without the guidance of another.
Immanuel Kant
It is the highest creatures who take the longest to mature, and are the most helpless during their immaturity.
George Bernard Shaw