The idiom 为所欲为 (wéi suǒ yù wéi), meaning "to do whatever one wants (often selfishly or lawlessly)", is formed through a distinct grammatical construction where the first 为 acts as a passive marker ("by"), 所 is a particle used in classical Chinese to introduce the agent of a passive verb, and 欲为 means "wants to do". Literally, it parses as "to be by that which one desires to do", but through idiomatic convention, it inverts to express the active sense of a person acting as the unchecked agent of their own desires, thus achieving its meaning of willful and arbitrary action.