Discussion is an exchange of knowledge; argument an exchange of ignorance.

Quillen contrasts two modes of talk. “Discussion” implies a cooperative search for understanding—participants share information, revise views, and treat the topic as larger than any one ego. “Argument,” in his sharper sense, is not reasoned debate but adversarial sparring: people trade assertions, slogans, and misunderstandings, often more invested in winning than in learning. The aphorism critiques the social psychology of conflict—how pride and identity can replace curiosity—while also offering a practical norm for dialogue: if the exchange is producing more heat than light, it has likely shifted from inquiry to performance. Its enduring appeal lies in how quickly it diagnoses unproductive conversation.