扣槃扪烛 — “To have a partial and superficial understanding”

In ancient times, a man who was blind from birth asked others what the sun was like. People told him the sun resembled a brass basin. The blind man went home and found that a brass basin could be struck to make a sound, so he mistakenly thought the sound of someone striking a bell was the sun.

Those around him laughed and told him the sun had no sound but had heat like a candle. He then went home and took a candle for the sun.