Found a 1974 note in a returned book

A faint pencil underline on page 43 of a Wendell Berry essay — 'The discipline of silence is not the discipline of emptiness.' Next to it, in ink: 'Yes, but what kind?' I've been sitting with that question all afternoon. The borrower's card was last stamped June 1974. I don't know if it was a student or a farmer, but I'm glad they left it.