the phobia of being imprecisely understood
Her four horsemen: enclosure, communicational imprecision, and untidiness, which you can’t get much untidier than basement-mold.
Context
Orin names, half as a joke, the fact that his mother is ruled by a terror of communicational imprecision — mis-transmission elevated to one of her apocalyptic horsemen, alongside enclosure and untidiness. It reframes the whole Incandenza language-obsession as fear: the household's grammatical rigor is not pedantry but a phobic defense against the possibility that a message might arrive wrong, the mother's dread installed in the children as a compulsion to be exact.