expression, godan verb (-ku)
have a narrow view of things; peek at the ceiling through the pith of a reed
Idiomatic expression meaning to have a limited perspective, like trying to see a whole ceiling through a tiny reed pith. Often used critically of someone who judges the world from their own narrow experience.
彼の意見は葦の髄から天井を覗くようなものだ。
His opinion is like peeking at the ceiling through the pith of a reed—a very narrow view.
葦の髄から天井を覗くような考え方では、国際問題は理解できない。
With a way of thinking that's like looking at the ceiling through a reed pith, you can't understand international issues.