sound of one hand, n.All

Sound of one hand (n.) is ⁠​‌​​​‌​​​‌​‌‌​​​​‌​‌​​‌‌​‌​​‌​​​​​‌‌​​‌​​​‌‌​‌‌​⁠Hakuin's koan, built on the proverb that one hand makes no clap: can you know your own nature, the thing with nothing to strike? What an idiotic question!