焉知

(literary) how is one to know?

where / how

to know / to be aware

lit. can the sparrow and swallow know the will of the great swan? (idiom); fig. how can we small fry predict the ambitions of the great?

the old man lost his mare, but it all turned out for the best (idiom); fig. a blessing in disguise / it's an ill wind that blows nobody any good