“Every now and then a man’s mind is stretched by a new idea or sensation, and never shrinks back to its former dimensions.”
The Autocrat persona pictures significant ideas and experiences as permanently enlarging the range through which a person can think.
Source details
The Autocrat of the Breakfast-Table, represented by Project Gutenberg #751. The line is spoken in Holmes’s table-talk authorial persona and followed by an Alpine image; it is a literary metaphor for intellectual expansion, not a neurological claim.