A kōan ( /ˈkoʊ.ɑːn/; Chinese: 公案; pinyin: gōng'àn; Korean: 공안 (kong'an); Vietnamese: công án) is a story, dialogue, question, or statement, which is used in Zen-practice to provoke the "great doubt", and test a student's progress in Zen practice.

The word koan, literally "public case", comes from the Japanese pronunciation of the Chinese characters (公案).

Kōan is a Japanese rendering of the Chinese term (公案), transliterated kung-an (Wade-Giles) or gōng'àn (Pinyin).

Chung Feng Ming Pen (中峰明本 1263–1323) wrote that kung-an is an abbreviation for kung-fu an-tu (公府之案牘, Pinyin gōngfǔ zhī àndú, pronounced in Japanese as kōfu no antoku), which referred to a "public record" or the "case records of a public law court" in Tang-dynasty China.Kōan/kung-an thus serves as a metaphor for principles of reality beyond the private opinion of one person, and a teacher may test the student's ability to recognize and understand that principle.

Commentaries in kōan collections bear some similarity to judicial decisions that cite and sometimes modify precedents. An article by T. Griffith Foulk claims

Jack Kornfield (born 1945) is a teacher in the vipassana movement of American Theravada Buddhism. He trained as a Buddhist monk in Thailand, Burma and India, including as a student of the Thai monk Ajahn Chah. He has taught meditation worldwide since around 1974.

After graduating from Dartmouth College in 1967, Kornfield joined the Peace Corps and was assigned to the Public Health Service in northeast Thailand, where there are several Buddhist forest monasteries. Here he met Ajahn Chah, who became his teacher. Upon returning to the United States in 1972, Kornfield co-founded the Insight Meditation Society in Barre, Massachusetts, with Sharon Salzberg and Joseph Goldstein.

Kornfield holds a Ph.D. in clinical psychology from Saybrook Institute. He is also a founding teacher of the Spirit Rock Center in Woodacre, California, where he currently lives.

Kornfield's work has focused on integrating Eastern spiritual teachings in an accessible way for Western students.

His books include

Kornfield lectures were featured by Joe Frank on his radio series "The Other Side."

Joe Frank (born August 19, 1938) is an American radio artist known best for his often philosophical, humorous, surrealist, and sometimes absurd monologues and radio dramas.

Joe Frank was born Joseph Langermann in August 1938 in Strasbourg, France near the border of Germany to Meier Langermann (then 51) and his wife Friederike (then 27), while in transit from Germany (where they were living, although they were Polish citizens). Being Jewish, his family was fleeing Nazi Germany and moving to New York City, where they arrived on April 12, 1939. Bills to allow the family into the country were passed in the U.S. Congress twice, the first having been vetoed by President Roosevelt. Joe's father died when he was 5 years old. The next year his mother married Freddy Frank and changed Joe's last name.

In his twenties, Frank studied at Hofstra University in New York and later at the Iowa Writers' Workshop. Frank taught English literature at the Dalton School in Manhattan when he became interested in the power of radio.