Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
FAULTY PARALLELISM
English teachers have long tried to root out faulty parallelisms, wherein, usually on either side of an and or a but, the writer places functionally different rather than functionally similar structures: He likes to swim and diving too. Only crude faulty parallelisms usually bother us; we speak and write a good many more that go unnoticed. One of the most noticeable, however, is the and who clause out of parallel with a preceding phrasal modifier: My father is a teacher very knowledgeable about his subject and who shows great enthusiasm as well. Say or write either My father is a teacher who is … and who shows … or My father is a teacher very knowledgeable … and very enthusiastic as well. See also PARALLELISM.
