“There may be said to be two classes of people in the world; those who constantly divide the people of the world into two classes, and those who do not. Both classes are extremely unpleasant to meet socially, leaving practically no one in the world whom one cares very much to know.”

Cassandra (1860)
Context: The progressive world is necessarily divided into two classes — those who take the best of what there is and enjoy it — those who wish for something better and try to create it. Without these two classes the world would be badly off. They are the very conditions of progress, both the one and the other. Were there none who were discontented with what they have, the world would never reach anything better.

Source: The Second Summer of the Sisterhood

The Tragic Sense of Life (1913), IX : Faith, Hope, and Charity

Source: The Way of All Flesh (1903), Ch. 26

Source: Still Life with Woodpecker (1980)

Change the World Without Taking Power (2002)

Vanity Fair (February 1920)
Variant: There may be said to be two classes of people in the world; those who constantly divide the people of the world into two classes, and those who do not.
Context: There may be said to be two classes of people in the world; those who constantly divide the people of the world into two classes, and those who do not. Both classes are extremely unpleasant to meet socially, leaving practically no one in the world whom one cares very much to know.

Humor in Psychotherapy (2007)