何以 is a literary adverb meaning 'how?' or 'why?'. It appears in formal or classical Chinese writing and in set phrases such as 何以见得 ('how do you know?'). Unlike colloquial 怎么 or 为什么, 何以 carries a refined, elevated tone and is rarely used in everyday speech. It is placed before the verb or predicate in a question: 何以 + verb phrase.