Inside he sat for a time doing nothing, not even thinking; his mind had become empty.

For a moment his mind became empty of all else.

I wonder if his mind can have become in any way unhinged.

Indeed his mind had become like a strongbox to which there was no key.

My mind, however, became as clear of thought as a fine summer sky.

My mind had become so dulled that I could no longer get upset about this fact.

My mind was becoming more and more active with questions.

It was as if, suddenly, his mind had become disembodied.

His mind became lively with the things he and Stony would say when they met.

How stiff and stuffy a mind can become with a little age on it.