The next sentence of neither supercilious nor supercilious is "neither arrogant nor impetuous", which comes from Nineteen Answers in a Small Room written by Zhu Zhiyu in the Ming Dynasty. The whole sentence is "sages have their own right way, neither humble nor supercilious, how can they be like this!"

Neither supercilious nor supercilious means neither supercilious nor supercilious. It describes a correct attitude towards people and a proper sense of proportion.