"Common Denominator" by John D. MacDonald is a science fiction novel written in the early 1950s. The story revolves around the interactions between humans and the Argonauts, an advanced alien civilization. It explores themes of societal evolution, the necessity for maturity in a species, and the consequences of unchecked human impulses. In the narrative, Lambert, a chief of the Bureau of Racial Maturity, becomes intrigued by the Argonauts after a successful cultural exchange. He discovers that the Argonauts had faced similar challenges to humanity but found a drastic solution to violence and instability: a form of self-administered euthanasia activated by a personal impulse to self-harm. This controversial practice allowed their society to thrive by weeding out potential sources of instability, ultimately leading to a content but stagnant civilization. The story culminates with Lambert reflecting on the implications of this practice and questioning if humanity could adopt such measures to survive its own destructive tendencies. Lambert's decision to leave his job in the ending suggests a broader contemplation on ethical governance and the future of humanity. (This is an automatically generated summary.)