The so-called discovery of childhood:
"Stages of life are artifacts, ideas with histories; the unborn, as a stage of life anyone could picture, dates only to the 1960s; adolescence is a useful contrivance; midlife is a moving target . . . . There have always been children, of course, but in other times and places, people have thought about them differently. The idea that children are born innocent and need protection from the world of adults is a product of the Enlightenment
. . . .
[Eventually] the amusing and precious and Lilliputian world of children had become a mainstay of Victorian middle-class culture: there were children's books, children's clothes, children's toys, and children's furniture . . . In the age of progress, with all of its machines, the world of adults was thought to be ruthless: cold, industrial, and grinding. Reformers wanted childhood, a world of little women and little men, to be a place apart, a paradise: the last mansion of happiness."
- Jill Lepore, The Mansion of Happiness