What are the motifs in It's like This by Stephen Dobyns?

Existence is a recurring idea. What is existence? this poem seems to be asking. Is it one's identity? If so, what does that mean? What is identity if everyone sees a person as someone that he or she is not? Should one conform to what others think, even if those definitions do not in any way match one's self-definition? Why do those definitions differ so widely?