koan
/ˈkəʊɑːn/noun
- a paradoxical anecdote or riddle without a solution, used in Zen Buddhism to demonstrate the inadequacy of logical reasoning and provoke enlightenment（佛教禅宗的）公案（悖论性轶事或不解之谜, 用以论证逻辑推理的不充分并启迪迷悟）。
词源
Japanese, literally 'matter for public thought', from Chinese gōngàn 'official business'.