expression
anyone can make a mistake; even Homer nods
Proverb meaning that even the wisest or most capable person can err. The literal image is that even a polished mirror cannot reflect its own back side.
彼ほどの専門家でも間違えることがある。明鏡も裏を照らさずだ。
Even an expert like him can make mistakes. Even a polished mirror cannot reflect its reverse side.
A classical Japanese proverb. The exact origin is uncertain, but it draws on the metaphor of a mirror that cannot show its own back.