This phrase, from The Analects, stands for extrapolating many things from one. It describes a state of learning that Confucius (551-479 BC) hoped his students would reach. The concept entails understanding the underlying principles of a single matter and using that knowledge to discern other matters that follow the same principles. Confucius used the metaphor of “one corner” and “three corners” to exemplify this process of knowledge extension, widely known as “drawing inferences by analogy.”

Confucius said, “I do not teach a student who is not eager to learn; I do not provide guidance to a student until he wishes to express himself but is unsure how to do it. If I impart one concept to him, and he fails to infer three other related aspects from it, then further instruction is futile. (The Analects)