u/BEADGCFBbEbAbDbGb

The ultimate metaphor in GONe is the keyholes, the fact that as humans we are like these infinite rooms of thoughts and associations trying to squeeze out and communicate with each other through these tiny keyholes. Another thread is logic as it pertains to true communication “You don’t feel anything about [formal logical theorems] they have no connotation.”
The character Neil also repeatedly references his introductory class to the subject throughout the story. Incidentally, every issue of the textbook “A concise introduction to logic” features a key on the cover.