物物而不物於物 Wùwù érbùwù yúwù. The genius of the tongue-twister can't be captured in translation but even if you don't know Chinese it is worth reading the italicized Pinyin aloud to get a feel for it. The trick lies in the fact that what we consider nouns can be used as verbs in Chinese. So, to "child" someone means to infantilize them. Literally, this lines reads, "thing thing not thing by thing," which means roughly, "treat things as things, don't be turned into things by things." It sheds light on Zhuangzi's understanding of a "thing" as implies being a tool, a means to an end. Thus, being a thing in the opposite of being useless.