This quote originates from God Bless You, Mr. Rosewater, a novel by Kurt Vonnegut Jr. published in 1965, capturing a bleak yet humanistic outlook prevalent in post-World War II American literature. Vonnegut, a keen observer of societal absurdities and human suffering, uses this statement to encapsulate his core ethical philosophy amidst a world he often depicted as chaotic and indifferent. The "rule" serves as a stark, secular commandment, urging empathy and compassion as the only truly meaningful directive in a seemingly meaningless existence.